Os cientistas usando o Telescópio Espacial Hubble da NASA/ESA produziram novos mapas de Júpiter, que mostram as contínuas mudanças que ocorrem com a famosa Grande Mancha Vermelha. As imagens também revelam uma rara estrutura em forma de onda na atmosfera do planeta que não tinha sido vista por décadas. A nova imagem é a primeira de uma série de retratos anuais dos planetas externos do Sistema Solar, que nos darão um novo olhar desses mundos remotos, e ajudarão os cientistas a estudarem como eles mudam com o passar do tempo.
Nessa nova imagem de Júpiter, uma grande quantidade de feições foi capturada incluindo ventos, nuvens e tempestades. Os cientistas por trás dessas novas imagens, as obtiveram usando a Wide Field Camera 3 do Hubble, num período de observação de mais de 10 horas e produziram assim dois mapas completos do planeta, a partir das suas observações. Esses mapas fizeram com que fosse possível determinar a velocidade dos ventos em Júpiter, com a finalidade de identificar diferentes fenômenos na sua atmosfera além de traquear as suas feições mais famosas.
As novas imagens confirmam que a grande tempestade que tem existido na superfície de nuvens de Júpiter por no mínimo 300 anos, continua a encolher, mas mesmo que desapareça, ela irá morrer lutando. A tempestade, conhecida como Grande Mancha Vermelha, é vista aqui fazendo seus movimentos em espiral no centro da imagem do planeta. Ela tem diminuído de tamanho de maneira muito rápida de ano em ano. Mas agora, a taxa de encolhimento parece ter reduzido novamente, mesmo apesar da mancha ser cerca de 240 quilômetros menor do que era em 2014.
Karakterisasi Letusan Merapi menggunakan Data SAR (Synthetic Aperture Radar)Achmad Darul
The document summarizes research using Synthetic Aperture Radar (SAR) data and other remote sensing data to characterize eruptions of Mount Merapi volcano in Indonesia over the last decade. SAR data from 1996-2006 was used to detect and analyze pyroclastic flow deposits from each eruption. ALOS/PALSAR SAR data observed the large 2010 eruption, detecting pyroclastic deposits 7 times larger than 2006. Interferometric SAR, thermal infrared data, and field measurements were used to analyze ground deformation, lava dome growth, and surface temperatures as precursors to the 2010 eruption. Inflation was detected in 2008 and 2010 via SAR interferometry.
Observed glacier and volatile distribution on Pluto from atmosphere–topograph...Sérgio Sacani
Pluto has a variety of surface frosts and landforms as well as a
complex atmosphere1. There is ongoing geological activity related
to the massive Sputnik Planum glacier, mostly made of nitrogen (N2)
ice mixed with solid carbon monoxide and methane2, covering the
4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planum1,3
near the anti-Charon point. The glacier has been suggested to arise
from a source region connected to the deep interior, or from a sink
collecting the volatiles released planetwide1. Thin deposits of N2
frost, however, were also detected at mid-northern latitudes and
methane ice was observed to cover most of Pluto except for the
darker, frost-free equatorial regions2. Here we report numerical
simulations of the evolution of N2, methane and carbon monoxide
on Pluto over thousands of years. The model predicts N2 ice
accumulation in the deepest low-latitude basin and the threefold
increase in atmospheric pressure that has been observed to occur
since 19884–6. This points to atmospheric–topographic processes as
the origin of Sputnik Planum’s N2 glacier. The same simulations also
reproduce the observed quantities of volatiles in the atmosphere and
show frosts of methane, and sometimes N2, that seasonally cover the
mid- and high latitudes, explaining the bright northern polar cap
reported in the 1990s7,8 and the observed ice distribution in 20152.
The model also predicts that most of these seasonal frosts should
disappear in the next decade.
Historical and Contemporary Trends in the Size, Drift, and Color of Jupiterʼs...Sérgio Sacani
The Great Red Spot on Jupiter has been shrinking over the past 150+ years based on historical records and spacecraft observations. Recent data from 1979-2017 show the Spot shrinking longitudinally at a rate of 0.194 degrees per year and latitudinally at 0.048 degrees per year. Its westward drift has also been accelerating, increasing about 0.002 degrees per day each year. High resolution images allow analysis of changes in the Spot's color, winds, and internal structure over this time period.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
Galaxy dynamics and the mass density of the universeSérgio Sacani
Dynamical evidence accumulated over the
past 20 years has convinced astronomers that luminous matter
in a spiral galaxy constitutes no more than 10% of the mass of
a galaxy. An additional 90% is inferred by its gravitational
effect on luminous material. Here I review recent observations
concerning the distribution of luminous and nonluminous
matter in the Milky Way, in galaxies, and in galaxy clusters.
Observations of neutral hydrogen disks, some extending in
radius several times the optical disk, confirm that a massive
dark halo is a major component of virtually every spiral. A
recent surprise has been the discovery that stellar and gas
motions in ellipticals are enormously complex. To date, only for
a few spheroidal galaxies do the velocities extend far enough to
probe the outer mass distribution. But the diverse kinematics
of inner cores, peripheral to deducing the overall mass distribution,
offer additional evidence that ellipticals have acquired
gas-rich systems after initial formation. Dynamical results are
consistent with a low-density universe, in which the required
dark matter could be baryonic. On smallest scales of galaxies
[10 kiloparsec (kpc); H. = 50 kmsec'lmegaparsec'11 the
luminous matter constitutes only 1% of the closure density. On
scales greater than binary galaxies (i.e., .100 kpc) all systems
indicate a density -10% of the closure density, a density
consistent with the low baryon density in the universe. If
large-scale motions in the universe require a higher mass
density, these motions would constitute the first dynamical
evidence for nonbaryonic matter in a universe of higher
density.
A new study developed three algorithms to automatically determine the boundaries of scatter plots used in the triangle method for estimating evapotranspiration from satellite data. The algorithms were tested on data from northern China and showed improved consistency over manual boundary selection. Algorithm II performed best by separating scatter plots into upper and lower regions before boundary fitting. The new automatic method enables more objective and repeatable evapotranspiration estimates at regional scales from remote sensing data.
On some structural_features_of_the_metagalaxySérgio Sacani
Progress in a group of investigations designed
to discover some of the structural details in individual galaxies and in the
Metagalaxy is reported in the following pages.
(a) The first section is concerned with the distribution of cluster-type
Cepheids in high galactic latitude. To the 169 already known in latitudes,
greater than or equal to ± 20o
, the systematic variable star programme carried
on at Harvard has added 312, mostly fainter than magnitude 13-0. With
allowance for absorption and for uncertainties yet remaining in the mean
absolute magnitude of these stars, the thickness of the Milky Way, so far
as this type of star is concerned, is not less than twenty-five kiloparsecs ;
he extent of the Milky Way in its own plane, by the same criterion, is more
than thirty kiloparsecs, perhaps much more.
(b) The extent of the Milky Way in the anti-centre quadrant is considered
on the basis of classical and cluster-type Cepheids ; provisionally
it is found that the galactic system reaches to a distance of at least ten
kiloparsecs in longitude 150o
.
(r) More than six hundred new variables have been found in the Large
Magellanic Cloud and measured for position, ranges and median magnitudes ;
the frequency of periods is not unlike that for the classical Cepheids in the
galactic system ; the light curves also are comparable in all details. The
Magellanic Cepheids, like the galactic classical Cepheids, are concentrated
in regions of high star-density.
(d) Further study of the period-luminosity relation in the Large Magellanic
Cloud permits its revision and strengthening for the Cepheids of
highest absolute magnitude. An observed deviation from the relation
that had previously been found for the Small Cloud is probably to be
attributed to scale error in the magnitude system. No seriously disturbing
Karakterisasi Letusan Merapi menggunakan Data SAR (Synthetic Aperture Radar)Achmad Darul
The document summarizes research using Synthetic Aperture Radar (SAR) data and other remote sensing data to characterize eruptions of Mount Merapi volcano in Indonesia over the last decade. SAR data from 1996-2006 was used to detect and analyze pyroclastic flow deposits from each eruption. ALOS/PALSAR SAR data observed the large 2010 eruption, detecting pyroclastic deposits 7 times larger than 2006. Interferometric SAR, thermal infrared data, and field measurements were used to analyze ground deformation, lava dome growth, and surface temperatures as precursors to the 2010 eruption. Inflation was detected in 2008 and 2010 via SAR interferometry.
Observed glacier and volatile distribution on Pluto from atmosphere–topograph...Sérgio Sacani
Pluto has a variety of surface frosts and landforms as well as a
complex atmosphere1. There is ongoing geological activity related
to the massive Sputnik Planum glacier, mostly made of nitrogen (N2)
ice mixed with solid carbon monoxide and methane2, covering the
4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planum1,3
near the anti-Charon point. The glacier has been suggested to arise
from a source region connected to the deep interior, or from a sink
collecting the volatiles released planetwide1. Thin deposits of N2
frost, however, were also detected at mid-northern latitudes and
methane ice was observed to cover most of Pluto except for the
darker, frost-free equatorial regions2. Here we report numerical
simulations of the evolution of N2, methane and carbon monoxide
on Pluto over thousands of years. The model predicts N2 ice
accumulation in the deepest low-latitude basin and the threefold
increase in atmospheric pressure that has been observed to occur
since 19884–6. This points to atmospheric–topographic processes as
the origin of Sputnik Planum’s N2 glacier. The same simulations also
reproduce the observed quantities of volatiles in the atmosphere and
show frosts of methane, and sometimes N2, that seasonally cover the
mid- and high latitudes, explaining the bright northern polar cap
reported in the 1990s7,8 and the observed ice distribution in 20152.
The model also predicts that most of these seasonal frosts should
disappear in the next decade.
Historical and Contemporary Trends in the Size, Drift, and Color of Jupiterʼs...Sérgio Sacani
The Great Red Spot on Jupiter has been shrinking over the past 150+ years based on historical records and spacecraft observations. Recent data from 1979-2017 show the Spot shrinking longitudinally at a rate of 0.194 degrees per year and latitudinally at 0.048 degrees per year. Its westward drift has also been accelerating, increasing about 0.002 degrees per day each year. High resolution images allow analysis of changes in the Spot's color, winds, and internal structure over this time period.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
Galaxy dynamics and the mass density of the universeSérgio Sacani
Dynamical evidence accumulated over the
past 20 years has convinced astronomers that luminous matter
in a spiral galaxy constitutes no more than 10% of the mass of
a galaxy. An additional 90% is inferred by its gravitational
effect on luminous material. Here I review recent observations
concerning the distribution of luminous and nonluminous
matter in the Milky Way, in galaxies, and in galaxy clusters.
Observations of neutral hydrogen disks, some extending in
radius several times the optical disk, confirm that a massive
dark halo is a major component of virtually every spiral. A
recent surprise has been the discovery that stellar and gas
motions in ellipticals are enormously complex. To date, only for
a few spheroidal galaxies do the velocities extend far enough to
probe the outer mass distribution. But the diverse kinematics
of inner cores, peripheral to deducing the overall mass distribution,
offer additional evidence that ellipticals have acquired
gas-rich systems after initial formation. Dynamical results are
consistent with a low-density universe, in which the required
dark matter could be baryonic. On smallest scales of galaxies
[10 kiloparsec (kpc); H. = 50 kmsec'lmegaparsec'11 the
luminous matter constitutes only 1% of the closure density. On
scales greater than binary galaxies (i.e., .100 kpc) all systems
indicate a density -10% of the closure density, a density
consistent with the low baryon density in the universe. If
large-scale motions in the universe require a higher mass
density, these motions would constitute the first dynamical
evidence for nonbaryonic matter in a universe of higher
density.
A new study developed three algorithms to automatically determine the boundaries of scatter plots used in the triangle method for estimating evapotranspiration from satellite data. The algorithms were tested on data from northern China and showed improved consistency over manual boundary selection. Algorithm II performed best by separating scatter plots into upper and lower regions before boundary fitting. The new automatic method enables more objective and repeatable evapotranspiration estimates at regional scales from remote sensing data.
On some structural_features_of_the_metagalaxySérgio Sacani
Progress in a group of investigations designed
to discover some of the structural details in individual galaxies and in the
Metagalaxy is reported in the following pages.
(a) The first section is concerned with the distribution of cluster-type
Cepheids in high galactic latitude. To the 169 already known in latitudes,
greater than or equal to ± 20o
, the systematic variable star programme carried
on at Harvard has added 312, mostly fainter than magnitude 13-0. With
allowance for absorption and for uncertainties yet remaining in the mean
absolute magnitude of these stars, the thickness of the Milky Way, so far
as this type of star is concerned, is not less than twenty-five kiloparsecs ;
he extent of the Milky Way in its own plane, by the same criterion, is more
than thirty kiloparsecs, perhaps much more.
(b) The extent of the Milky Way in the anti-centre quadrant is considered
on the basis of classical and cluster-type Cepheids ; provisionally
it is found that the galactic system reaches to a distance of at least ten
kiloparsecs in longitude 150o
.
(r) More than six hundred new variables have been found in the Large
Magellanic Cloud and measured for position, ranges and median magnitudes ;
the frequency of periods is not unlike that for the classical Cepheids in the
galactic system ; the light curves also are comparable in all details. The
Magellanic Cepheids, like the galactic classical Cepheids, are concentrated
in regions of high star-density.
(d) Further study of the period-luminosity relation in the Large Magellanic
Cloud permits its revision and strengthening for the Cepheids of
highest absolute magnitude. An observed deviation from the relation
that had previously been found for the Small Cloud is probably to be
attributed to scale error in the magnitude system. No seriously disturbing
A 2 4_determination_of_the_local_value_of_the_hubble_constantSérgio Sacani
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to
reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%.
The bulk of this improvement comes from new, near-infrared observations of Cepheid
variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling
the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these
in turn leverage the magnitude-redshift relation based on 300 SNe Ia at z <0.15. All
19 hosts as well as the megamaser system NGC4258 have been observed with WFC3
in the optical and near-infrared, thus nullifying cross-instrument zeropoint errors in the
relative distance estimates from Cepheids. Other noteworthy improvements include a
33% reduction in the systematic uncertainty in the maser distance to NGC4258, a larger
sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to
the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of
Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW)
Cepheids.
This study analyzed transit observations of the Neptune-mass exoplanet GJ 436b taken with the Hubble Space Telescope. The transmission spectrum was found to be featureless, ruling out cloud-free hydrogen-dominated atmosphere models with high significance. The flat transmission spectrum is consistent with either an atmosphere containing high-altitude clouds located at a pressure of around 1 millibar, or a relatively hydrogen-poor atmosphere with 3% hydrogen and helium by mass. Bayesian atmospheric modeling showed that cloudy hydrogen-dominated or high-metallicity hydrogen-poor atmospheres provide the best fits to the data. Further observations are needed to distinguish between these scenarios.
Kepler-1647b is the largest and longest-period Kepler transiting circumbinary planet discovered to date. It orbits an eclipsing binary star system with an orbital period of approximately 1100 days, making it one of the longest-period transiting planets known. The planet is around 1.06 times the size of Jupiter and perturbes the times of the stellar eclipses, allowing its mass to be measured at 1.52 times that of Jupiter. Despite its long orbital period compared to Earth, the planet resides in the habitable zone of the binary star system throughout its orbit. The discovery of this unusual planetary system provides insights into theories of planet formation and dynamics in multiple star systems.
Remote Sensing Methods for operational ET determinations in the NENA region, ...NENAwaterscarcity
Workshop on Operationalizing the Regional Collaborative Platform to Address ‘Water Consumption, Water Productivity and Drought Management’ in Agriculture, 27 - 29 October 2015, Cairo, Egypt
A terrestrial planet_candidate_in_a_temperate_orbit_around_proxima_centauriSérgio Sacani
At a distance of 1.295 parsecs,1 the red-dwarf Proxima Centauri (α Centauri C, GL 551,
HIP 70890, or simply Proxima) is the Sun’s closest stellar neighbour and one of the best studied
low-mass stars. It has an effective temperature of only 3050 K, a luminosity of 0.1 per
cent solar, a measured radius of 0.14 R⊙
2 and a mass of about 12 per cent the mass of the
Sun. Although Proxima is considered a moderately active star, its rotation period is 83
days,3 and its quiescent activity levels and X-ray luminosity4 are comparable to the Sun’s. New
observations reveal the presence of a small planet orbiting Proxima with a minimum mass of
1.3 Earth masses and an orbital period of 11.2 days. Its orbital semi-major axis is 0.05 AU,
with an equilibrium temperature in the range where water could be liquid on its surface.5
Evapotranspiration estimation with remote sensingIqura Malik
This document provides an overview of estimating evapotranspiration (ET) using remote sensing. It discusses several methods and satellites used for deriving ET estimates remotely, including the Landsat, MODIS, Sentinel-2, and MSG programs. The MOD16 and LSA-SAF MSG algorithms for calculating ET from MODIS and MSG data respectively are described in detail. A case study is mentioned that compares ET estimates from the MOD16 and LSA-SAF MSG products.
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
This document summarizes a book about using GPS for precise relative positioning of formation flying satellites. The book focuses on using dual-frequency GPS data and integer ambiguity resolution to determine relative positions between satellites with accuracy of a few millimeters. It describes processing techniques like the Lambda method to resolve integer ambiguities in real-time. Formation flying has benefits for earth observation and gravity field mapping missions by coordinating smaller satellites.
Плутон светится в рентгеновском диапазонеAnatol Alizar
Chandra detected X-rays from Pluto in 2014 and 2015 observations, finding 8 photons in the 0.31-0.60 keV band. No photons were detected from 0.60-1.0 keV. Allowing for background, there was a statistically significant detection of X-rays from Pluto. Charge exchange between solar wind ions and Pluto's atmosphere can produce X-rays and may explain the detection, but the observed rate is higher than expected given New Horizons measurements of Pluto's atmosphere and solar wind conditions. The solar wind may be focused within 60,000 km of Pluto to produce the detected X-ray emission.
Hankerson_2012_Estimation of evapotranspiration from fields with and without ...Brett Hankerson
This document summarizes a study that used the METRIC (Mapping Evapotranspiration at high Resolution with Internalized Calibration) model to estimate evapotranspiration (ETa) rates from fields with cover crops and fields without cover crops in northeastern South Dakota. The study utilized remote sensing imagery from 9 dates between May and October, including 5 dates during the cover crop season. METRIC estimates of ETa were compared to ETa estimates from a Bowen-Ratio Energy Balance System (BREBS) and were found to successfully differentiate between fields with and without cover crops, with the METRIC estimates being within 7% of the BREBS estimates for the cover crop season.
This document analyzes carbon flux estimations in the Arctic based on MODIS vegetation indices. It aims to improve understanding of CO2 dynamics in the Arctic by upscaling satellite data to model Net Ecosystem Exchange (NEE). The study evaluates four MODIS products - MCD15A3, MOD13A1, MOD13Q1, and MYD09GA - to determine which best estimates NEE based on vegetation indices like LAI and NDVI at 12 Arctic sites. Results show that MOD13Q1, with 250m resolution and 16-day temporal resolution, provides the best NEE estimations compared to the other products and field data. Finer spatial resolution is needed to accurately model Arctic landscape heterogeneity and carbon
Met Éireann has expanded from monitoring Irish climate to conducting climate modelling. It was initially involved in regional climate modelling through projects like C4I. It has since joined the EC-Earth consortium to run its own global climate model. EC-Earth simulations will be contributed to CMIP5 and used for national climate impact research. Met Éireann also maintains regional modelling capabilities and plans high-resolution regional simulations.
The document summarizes research from images taken by the New Horizons spacecraft of Charon, Pluto's largest moon. The images reveal Charon has a reddish polar cap at its north pole. Thermal models show the pole experiences long periods of extreme cold temperatures due to Charon's high obliquity and long seasons. The researchers hypothesize that methane and other volatiles escaping from Pluto's atmosphere become cold-trapped at Charon's winter pole, where they are processed by radiation into non-volatile organic compounds that remain on the surface to form the red cap. Spectral and compositional evidence supports this mechanism of seasonal accumulation of photolyzed volatiles to explain Charon's unique polar color
Атмосфера Земли медленно теряет кислородAnatol Alizar
This document summarizes research on reconstructing past atmospheric oxygen (O2) levels over the past 800,000 years using O2/N2 ratios measured from ancient air bubbles trapped in ice cores from Greenland and Antarctica. The main findings are:
1) O2/N2 ratios from multiple ice cores show a consistent decline of 8.4‰ per million years over the past 800,000 years, equivalent to a 0.7% decline in atmospheric O2 levels.
2) This decline is unlikely to be explained by changes in air bubble formation processes or other non-atmospheric factors, as argon/nitrogen ratios from the same ice cores show an inconsistent increasing trend over the same
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
This document reports the discovery of a newly discovered optical Einstein ring (ER) called the "Canarias Einstein Ring". It was discovered serendipitously in imaging data from the Dark Energy Camera. Follow-up spectroscopy with the Gran Telescopio CANARIAS confirmed the nature of the system, with the lens being an early-type galaxy at a redshift of z=0.581 and the source being a starburst galaxy at z=1.165. Analysis of the system determined the Einstein radius to be 2.16 arcseconds and the total enclosed mass producing the lensing effect to be 1.86 ± 0.23 × 1012 solar masses.
The wonderful complexity_of_the_mira_ab_systemSérgio Sacani
The ALMA observations of the Mira AB binary system reveal an amazingly complex circumstellar environment shaped by multiple dynamical processes. In the blue wing of the CO emission line, opposing large arcs form a bubble structure around Mira A, possibly created by the wind from Mira B blowing into Mira A's expanding envelope. In the main line component, spiral arcs are seen around Mira A that appear relatively flat and oriented in the orbital plane. An accretion wake is also visible trailing Mira B. The companion is marginally resolved with a separation of 0.487 arcseconds from Mira A.
This document summarizes research using pulsar timing array data to search for gravitational waves from binary supermassive black holes. The authors analyzed 11 years of timing data for 4 millisecond pulsars and placed an upper limit on the characteristic strain amplitude of the gravitational wave background of Ac,yr < 1.0×10-15 at 95% confidence. This limit is inconsistent with current models of binary supermassive black hole evolution and gravitational wave emission. It suggests binary evolution may be more efficient than assumed or the gravitational wave background is weaker than predicted. Improved pulsar timing data could help distinguish between possible explanations for the non-detection.
The high mass_stelar_initial_mass_function_in_m31_clustersSérgio Sacani
Em uma pesquisa feita com o Telescópio Espacial Hubble da NASA, analisando imagens de 2753 jovens, aglomerados estelares azuis, na vizinha galáxia de Andrômeda, a M31, os astrônomos descobriram que a M31 e a nossa própria galáxia, possuem uma porcentagem similar de estrelas recém-nascidas, com base na massa estudada.
Identificando qual porcentagem de estrelas tem uma massa particular, dentro de um aglomerado, ou sua Função de Massa Inicial, IMF, os cientistas podem interpretar melhor a luz de galáxias distantes e entender a história de formação das estrelas no universo.
A intensa pesquisa, agrupou 414 mosaicos fotográficos feitos pelo Hubble da M31, uma colaboração única feita entre astrônomos, cientistas cidadãos, voluntários que forneceram uma ajuda valiosa em analisar a montanha de dados do Hubble.
“Dada a quantidade de imagens do Hubble, nosso estudo da IMF, não seria possível sem a ajuda dos cientistas cidadãos”, disse Daniel Weisz, da Universidade de Washington em Seatle. Weisz, é o principal autor do artigo que foi publicado no dia 20 de Junho no The Astrophysical Journal.
A 2 4_determination_of_the_local_value_of_the_hubble_constantSérgio Sacani
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to
reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%.
The bulk of this improvement comes from new, near-infrared observations of Cepheid
variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling
the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these
in turn leverage the magnitude-redshift relation based on 300 SNe Ia at z <0.15. All
19 hosts as well as the megamaser system NGC4258 have been observed with WFC3
in the optical and near-infrared, thus nullifying cross-instrument zeropoint errors in the
relative distance estimates from Cepheids. Other noteworthy improvements include a
33% reduction in the systematic uncertainty in the maser distance to NGC4258, a larger
sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to
the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of
Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW)
Cepheids.
This study analyzed transit observations of the Neptune-mass exoplanet GJ 436b taken with the Hubble Space Telescope. The transmission spectrum was found to be featureless, ruling out cloud-free hydrogen-dominated atmosphere models with high significance. The flat transmission spectrum is consistent with either an atmosphere containing high-altitude clouds located at a pressure of around 1 millibar, or a relatively hydrogen-poor atmosphere with 3% hydrogen and helium by mass. Bayesian atmospheric modeling showed that cloudy hydrogen-dominated or high-metallicity hydrogen-poor atmospheres provide the best fits to the data. Further observations are needed to distinguish between these scenarios.
Kepler-1647b is the largest and longest-period Kepler transiting circumbinary planet discovered to date. It orbits an eclipsing binary star system with an orbital period of approximately 1100 days, making it one of the longest-period transiting planets known. The planet is around 1.06 times the size of Jupiter and perturbes the times of the stellar eclipses, allowing its mass to be measured at 1.52 times that of Jupiter. Despite its long orbital period compared to Earth, the planet resides in the habitable zone of the binary star system throughout its orbit. The discovery of this unusual planetary system provides insights into theories of planet formation and dynamics in multiple star systems.
Remote Sensing Methods for operational ET determinations in the NENA region, ...NENAwaterscarcity
Workshop on Operationalizing the Regional Collaborative Platform to Address ‘Water Consumption, Water Productivity and Drought Management’ in Agriculture, 27 - 29 October 2015, Cairo, Egypt
A terrestrial planet_candidate_in_a_temperate_orbit_around_proxima_centauriSérgio Sacani
At a distance of 1.295 parsecs,1 the red-dwarf Proxima Centauri (α Centauri C, GL 551,
HIP 70890, or simply Proxima) is the Sun’s closest stellar neighbour and one of the best studied
low-mass stars. It has an effective temperature of only 3050 K, a luminosity of 0.1 per
cent solar, a measured radius of 0.14 R⊙
2 and a mass of about 12 per cent the mass of the
Sun. Although Proxima is considered a moderately active star, its rotation period is 83
days,3 and its quiescent activity levels and X-ray luminosity4 are comparable to the Sun’s. New
observations reveal the presence of a small planet orbiting Proxima with a minimum mass of
1.3 Earth masses and an orbital period of 11.2 days. Its orbital semi-major axis is 0.05 AU,
with an equilibrium temperature in the range where water could be liquid on its surface.5
Evapotranspiration estimation with remote sensingIqura Malik
This document provides an overview of estimating evapotranspiration (ET) using remote sensing. It discusses several methods and satellites used for deriving ET estimates remotely, including the Landsat, MODIS, Sentinel-2, and MSG programs. The MOD16 and LSA-SAF MSG algorithms for calculating ET from MODIS and MSG data respectively are described in detail. A case study is mentioned that compares ET estimates from the MOD16 and LSA-SAF MSG products.
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
This document summarizes a book about using GPS for precise relative positioning of formation flying satellites. The book focuses on using dual-frequency GPS data and integer ambiguity resolution to determine relative positions between satellites with accuracy of a few millimeters. It describes processing techniques like the Lambda method to resolve integer ambiguities in real-time. Formation flying has benefits for earth observation and gravity field mapping missions by coordinating smaller satellites.
Плутон светится в рентгеновском диапазонеAnatol Alizar
Chandra detected X-rays from Pluto in 2014 and 2015 observations, finding 8 photons in the 0.31-0.60 keV band. No photons were detected from 0.60-1.0 keV. Allowing for background, there was a statistically significant detection of X-rays from Pluto. Charge exchange between solar wind ions and Pluto's atmosphere can produce X-rays and may explain the detection, but the observed rate is higher than expected given New Horizons measurements of Pluto's atmosphere and solar wind conditions. The solar wind may be focused within 60,000 km of Pluto to produce the detected X-ray emission.
Hankerson_2012_Estimation of evapotranspiration from fields with and without ...Brett Hankerson
This document summarizes a study that used the METRIC (Mapping Evapotranspiration at high Resolution with Internalized Calibration) model to estimate evapotranspiration (ETa) rates from fields with cover crops and fields without cover crops in northeastern South Dakota. The study utilized remote sensing imagery from 9 dates between May and October, including 5 dates during the cover crop season. METRIC estimates of ETa were compared to ETa estimates from a Bowen-Ratio Energy Balance System (BREBS) and were found to successfully differentiate between fields with and without cover crops, with the METRIC estimates being within 7% of the BREBS estimates for the cover crop season.
This document analyzes carbon flux estimations in the Arctic based on MODIS vegetation indices. It aims to improve understanding of CO2 dynamics in the Arctic by upscaling satellite data to model Net Ecosystem Exchange (NEE). The study evaluates four MODIS products - MCD15A3, MOD13A1, MOD13Q1, and MYD09GA - to determine which best estimates NEE based on vegetation indices like LAI and NDVI at 12 Arctic sites. Results show that MOD13Q1, with 250m resolution and 16-day temporal resolution, provides the best NEE estimations compared to the other products and field data. Finer spatial resolution is needed to accurately model Arctic landscape heterogeneity and carbon
Met Éireann has expanded from monitoring Irish climate to conducting climate modelling. It was initially involved in regional climate modelling through projects like C4I. It has since joined the EC-Earth consortium to run its own global climate model. EC-Earth simulations will be contributed to CMIP5 and used for national climate impact research. Met Éireann also maintains regional modelling capabilities and plans high-resolution regional simulations.
The document summarizes research from images taken by the New Horizons spacecraft of Charon, Pluto's largest moon. The images reveal Charon has a reddish polar cap at its north pole. Thermal models show the pole experiences long periods of extreme cold temperatures due to Charon's high obliquity and long seasons. The researchers hypothesize that methane and other volatiles escaping from Pluto's atmosphere become cold-trapped at Charon's winter pole, where they are processed by radiation into non-volatile organic compounds that remain on the surface to form the red cap. Spectral and compositional evidence supports this mechanism of seasonal accumulation of photolyzed volatiles to explain Charon's unique polar color
Атмосфера Земли медленно теряет кислородAnatol Alizar
This document summarizes research on reconstructing past atmospheric oxygen (O2) levels over the past 800,000 years using O2/N2 ratios measured from ancient air bubbles trapped in ice cores from Greenland and Antarctica. The main findings are:
1) O2/N2 ratios from multiple ice cores show a consistent decline of 8.4‰ per million years over the past 800,000 years, equivalent to a 0.7% decline in atmospheric O2 levels.
2) This decline is unlikely to be explained by changes in air bubble formation processes or other non-atmospheric factors, as argon/nitrogen ratios from the same ice cores show an inconsistent increasing trend over the same
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
This document reports the discovery of a newly discovered optical Einstein ring (ER) called the "Canarias Einstein Ring". It was discovered serendipitously in imaging data from the Dark Energy Camera. Follow-up spectroscopy with the Gran Telescopio CANARIAS confirmed the nature of the system, with the lens being an early-type galaxy at a redshift of z=0.581 and the source being a starburst galaxy at z=1.165. Analysis of the system determined the Einstein radius to be 2.16 arcseconds and the total enclosed mass producing the lensing effect to be 1.86 ± 0.23 × 1012 solar masses.
The wonderful complexity_of_the_mira_ab_systemSérgio Sacani
The ALMA observations of the Mira AB binary system reveal an amazingly complex circumstellar environment shaped by multiple dynamical processes. In the blue wing of the CO emission line, opposing large arcs form a bubble structure around Mira A, possibly created by the wind from Mira B blowing into Mira A's expanding envelope. In the main line component, spiral arcs are seen around Mira A that appear relatively flat and oriented in the orbital plane. An accretion wake is also visible trailing Mira B. The companion is marginally resolved with a separation of 0.487 arcseconds from Mira A.
This document summarizes research using pulsar timing array data to search for gravitational waves from binary supermassive black holes. The authors analyzed 11 years of timing data for 4 millisecond pulsars and placed an upper limit on the characteristic strain amplitude of the gravitational wave background of Ac,yr < 1.0×10-15 at 95% confidence. This limit is inconsistent with current models of binary supermassive black hole evolution and gravitational wave emission. It suggests binary evolution may be more efficient than assumed or the gravitational wave background is weaker than predicted. Improved pulsar timing data could help distinguish between possible explanations for the non-detection.
The high mass_stelar_initial_mass_function_in_m31_clustersSérgio Sacani
Em uma pesquisa feita com o Telescópio Espacial Hubble da NASA, analisando imagens de 2753 jovens, aglomerados estelares azuis, na vizinha galáxia de Andrômeda, a M31, os astrônomos descobriram que a M31 e a nossa própria galáxia, possuem uma porcentagem similar de estrelas recém-nascidas, com base na massa estudada.
Identificando qual porcentagem de estrelas tem uma massa particular, dentro de um aglomerado, ou sua Função de Massa Inicial, IMF, os cientistas podem interpretar melhor a luz de galáxias distantes e entender a história de formação das estrelas no universo.
A intensa pesquisa, agrupou 414 mosaicos fotográficos feitos pelo Hubble da M31, uma colaboração única feita entre astrônomos, cientistas cidadãos, voluntários que forneceram uma ajuda valiosa em analisar a montanha de dados do Hubble.
“Dada a quantidade de imagens do Hubble, nosso estudo da IMF, não seria possível sem a ajuda dos cientistas cidadãos”, disse Daniel Weisz, da Universidade de Washington em Seatle. Weisz, é o principal autor do artigo que foi publicado no dia 20 de Junho no The Astrophysical Journal.
Uma questão fundamental na astrobiologia, é: se a vida pode ser transportada entre planetas extrassolares, e sistemas planetários? Uma equipe de astrofísicos norte-americanos propôs uma nova estratégia para responder a essa questão com base no princípio que a vida alienígena que surgiu via espalhamento – num processo chamado de panspermia – exibirá mais aglomerados do que a vida que surge espontaneamente.
Existem duas maneiras básicas para a vida ter se espalhado além de sua estrela hospedeira.
A primeira seria por meio de um processo natural de arremessamento de asteroides e cometas. A segunda seria por meio da vida inteligente que deliberadamente viajaria pelo espaço.
Um novo artigo, aceito para publicação no Astrophysical Journal Letters, não lida como a panspermia ocorre. Ele simplesmente pergunta: se ela ocorreu, nós poderíamos detectá-la? Em princípio, a resposta é sim.
O modelo desenvolvido pela equipe no Harvard-Smithsonian Center for Astrophysics assume que as sementes de um planeta vivo se espalham em todas as direções.
O Telescópio Espacial Hubble das agências espaciais, NASA e ESA fez imagens de três magníficas seções da Nebulosa do Véu em 1997. Agora, um novo conjunto de imagens espetaculares feitas com a Wide Field Camera 3 do Hubble captura essa bela remanescente estelar com detalhes novos e surpreendentes e revela sua expansão nos últimos anos.
Derivando seu nome da delicada estrutura filamentar, a bela Nebulosa do Véu, é uma das remanescentes de supernovas mais conhecidas. Ela se formou da violenta morte de uma estrela com uma massa vinte vezes maior que a massa do Sol que explodiu a cerca de 8000 anos atrás. Localizada a aproximadamente 2100 anos-luz da Terra, na constelação de Cygnus, o Cisne, essa nuvem brilhante e colorida de detritos brilhantes se espalha por aproximadamente 110 anos-luz.
Em 1997, a Wide Field and Planetary Camera 2 do Hubble, a WFPC2, fotografou a Nebulosa do Véu, fornecendo visões detalhadas da sua estrutura. Agora, sobrepondo as imagens da WFPC2 com os novos dados obtidos pela Wide Field Camera 3, a WFC3, os cientistas podem ter acesso a detalhes ainda maiores de modo que eles possam estudar como a nebulosa se expandiu desde que ela foi fotografada a 18 anos atrás.
O centro da nossa Via Láctea é um lugar misterioso. Não somente está a milhares de anos-luz de distância, mas está também escondido sob grande quantidade de poeira de modo que a maior parte das estrelas em seu interior são invisíveis. Pesquisadores de Harvard, estão propondo uma nova maneira de limpar a neblina e registrar as estrelas ali escondidas. Eles sugerem observar os comprimentos de onda de rádio provenientes das estrelas supersônicas.
“Existem muitas, nós não sabemos sobre o centro galáctico, e nós queremos aprender muito”, disse o principal autor do estudo Idan Ginsburg do Harvard-Smithsonian Center for Astrophysics (CfA). “Usando essa técnica, nós podemos encontrar estrelas que ninguém observou antes”.
A grande trajetória do centro da nossa galáxia para a Terra é repleta de tanta poeira que até mesmo dos trilhões de fótons de luz visível que veem em nossa direção, somente um fóton atingirá nossos telescópios. Ondas de rádio, de uma diferente parte do espectro eletromagnético, possui energia mais baixa e comprimentos de onda maiores. Elas podem passar pela poeira de forma ilesa.
Uma equipe de astrônomos norte-americanos descobriu o par de buracos negros supermassivos mais próximos até agora no universo.
O par de buracos negros está localizado no centro do quasar chamado de PKS 1302-102, a aproximadamente 3.5 bilhões de anos-luz de distância.
Esses dois buracos negros estão separados de apenas uma semana-luz e estão num movimento espiral um em direção ao outro que deve acabar com uma colisão cataclísmica.
Em contraste, o par de buracos negros mais próximos descoberto até então estava separado de aproximadamente 20 anos-luz.
A propable milli_parsec_supermassive_binary_black_hole_in_the_nearest_quasar_...Sérgio Sacani
Astrônomos usando o Telescópio Espacial Hubble da NASA descobriram que a Markarian 231 (Mrk 231), a galáxia mais próxima da Terra que abriga um quasar, é alimentada por dois buracos negros centrais girando violentamente um em relação ao outro.
A descoberta sugere que os quasares, os brilhantes núcleos das galáxias ativas, podem normalmente abrigar dois buracos negros centrais que caem, um na órbita do outro como resultado da fusão de duas galáxias. Como um par de patinadores, o buraco negro duplo gera uma tremenda quantidade de energia que faz o núcleo da galáxia que o abriga se sobrepor ao brilho da população de bilhões de estrelas da galáxia, que os cientistas então identificam como quasares.
Os cientistas procuraram nas observações de arquivo do Hubble feitas na radiação ultravioleta emitida do centro da Mrk 231 para descobrir o que eles descrevem como propriedades extremas e surpreendentes.
The abundance of_x_shpoaed_radio_sources_implications_for_the_gravitational_w...Sérgio Sacani
Devem existir menos buracos negros supermassivos binários nos núcleos das galáxias do que se pensava anteriormente, disse uma equipe de cientistas da Universidade de Brandeis em Waltaham, Massachussets, e do Instituto de Pesquisa Raman em Bangalore, na Índia.
A maior parte das galáxias massivas no universo devem abrigar no mínimo um buraco negro supermassivo em seus núcleos.
Quando duas galáxias colidem, seus buracos negros se juntam, formando uma dança colossal que resulta numa combinação de par. Esse processo é a mais intensa fonte de ondas gravitacionais no universo, que ainda precisam ser diretamente detectadas.
“As ondas gravitacionais representam a próxima fronteira da astrofísica, e sua detecção levará a novas ideias sobre o universo. É importante se ter a maior quantidade de informação possível sobre as fontes dessas ondas”, disse o Dr. David Roberts, um membro da equipe da Universidade de Brandeis.
An evolucionary missing_link_a_modest_mass_early_type_galaxy_hosting_an_over_...Sérgio Sacani
O buraco negro supermassivo de uma galáxia descoberta recentemente é bem maior do seria possível, de acordo com as atuais teorias da evolução galáctica. Novo trabalho, realizado por astrônomos na Universidade Keele e da Universidade Central Lancashire, mostra que o buraco negro é muito massivo do que deveria ser, se comparado com a massa da galáxia ao redor. Os cientistas publicaram os resultados em um artigo no Monthly Notices of The Royal Astronomical Society.
A galáxia, SAGE0536AGN, foi inicialmente descoberta com o Telescópio Espacial Spitzer da NASA na luz infravermelha. Apesar de ter no mínimo 9 bilhões de anos de vida, ela contém um núcleo galáctico ativo, um AGN, um objeto incrivelmente brilhante resultante da acreção de gás por um buraco negro supermassivo central. O gás é acelerado a altíssimas velocidades devido ao imenso campo gravitacional do buraco negro, fazendo com que o gás emita luz.
A equipe agora também confirmou a presença de um buraco negro medindo a velocidade do gás movendo-se ao seu redor. Usando o Southern African LArge Telescope, os cientistas observaram que uma linha de emissão de hidrogênio, no espectro da galáxia (onde a luz é dispersada em suas diferentes cores – um efeito similar é visto usando um prisma) é alargada pelo Efeito Doppler, onde o comprimento de onda (a cor) da luz de um objeto é desviada para o azul e para o vermelho dependendo se ele está se movendo para perto ou para longe nós. O grau de alargamento implica que o gás está se movendo ao redor numa alta velocidade, um resultado do forte campo gravitacional do buraco negro.
An extreme starburst_in_the_core_of_a_rich_galaxy_cluster_at_z_1_7Sérgio Sacani
Os astrônomos descobriram um raro tipo de aglomerado de galáxias que tem seu coração repleto de novas estrelas. A descoberta inesperada, aconteceu com a ajuda dos telescópios espaciais da NASA Spitzer e Hubble, e sugere que galáxias gigantescas no núcleo desses aglomerados massivos podem crescer de maneira significante se alimentando de gás roubado de outras galáxias.
“Normalmente, as estrelas no centro dos aglomerados de galáxias, são velhas e mortas, essencialmente fósseis estelares”, disse Tracy Webb da Universidade McGill, em Montreal, no Canadá, principal autor do artigo que descreve as descobertas publicado na edição de 20 de Agosto do Teh Astrophysical Journal. “Mas nós acreditamos que a gigantesca galáxia no centro desse aglomerado está gerando novas estrelas de maneira furiosa depois de realizar uma fusão com uma galáxia menor”.
Os aglomerados de galáxias são grandes famílias de galáxias unidas e agrupadas pela gravidade. A nossa Via Láctea reside em um pequeno grupo de galáxias, chamado de Grupo Local, que por sua vez reside na periferia do gigantesco superaglomerado de galáxias Lanikea com 100000 galáxias (Lanikea signifiva “céu imensurável” em havaiano).
O aglomerado nesse novo estudo, é chamado pelos astrônomos de SpARCS1049+56, e tem no mínimo 27 galáxias, e uma massa combinada equivalente a 400 trilhões sóis. Ele está localizado a cerca de 9.8 bilhões de anos-luz na direção da constelação de Ursa Major. O objeto foi inicialmente descoberto usando o Spitzer e o Telescópio Canadá-França-Havaí, localizado no monte Mauna Kea no Havaí, e confirmado, usando o Observatório W.M. Keck, também no Mauna Kea.
Fifteen years of_xmm_newton_and_chandra_monitoring_of_sgr_a_evidence_for_a_re...Sérgio Sacani
Três telescópios de raios-X têm monitorado o buraco negro supermassivo no centro da Via Láctea, na última década e meia observando o seu comportamento. Essa longa campanha de monitoramento tem revelado algumas novas mudanças nos padrões desse buraco negro de 4 milhões de massas solares conhecido como Sagittarius A* (Sgr A*).
O painel inferior do gráfico principal desse post é uma visão da região ao redor do Sgr A*, onde as cores vermelha, verde e azul, representam os raios-X de baixa, média e alta energia detectados pelo Observatório de Raios-X Chandra da NASA. O Sgr A* não é visto na imagem, mas ele está mergulhado no ponto brando na ponta final da seta. Os outros dois telescópios envolvidos nessas observações de raios-X de 15 anos foram o XMM-Newton da ESA e o Swift Gamma Ray Burst Explorer da NASA, mas seus dados não estão incluídos nessa imagem.
Dentro do último ano, o buraco negro normalmente tranquilo, tem mostrado um aumento no nível de flares de raios-X com relação à sua taxa típica. Esse aumento nos flares de raios-X coincide com a passagem perto do Sgr A* do misterioso objeto chamado G2. Os astrônomos estão rastreando o G2 por anos, pensado originalmente como uma extensa nuvem de gás e poeira. Contudo, depois da passagem próxima do Sgr A* no final de 2013 sua aparência não mudou muito, a menos do fato de ter sido levemente estirado pela gravidade do buraco negro. Isso levou a novas teorias que o G2 não era uma nuvem de gás, mas uma estrela ou um par de estrelas dentro de um casulo empoeirado.
Detection of magnetic_fields_in_both_b_type_components_of_epsilon_lupi_system...Sérgio Sacani
Uma equipe de astrônomos detectou um chamado campo magnético fóssil em ambos os componentes de um sistema estelar binário, chamado de Epsilon Lupi.
Epsilon Lupi, também conhecida como HD 136504, é uma estrela binária brilhante, localizada na constelação do hemisfério sul de Lupus.
O par de estrelas está localizado a aproximadamente 500 anos-luz de distância da Terra, e cada estrela tem entre 7 e 8 vezes a massa do Sol, e combinadas, elas têm cerca de 6000 vezes a luminosidade do Sol.
Os astrônomos sabem de muito tempo que a Epsilon Lupi é um sistema binário, mas não tinham ideia de que as duas estrelas pudessem possuir campos magnéticos.
“A origem do magnetismo entre estrelas massivas é um mistério e essa descoberta pode ajudar a trazer uma luz numa questão de por que essas estrelas possuem campos magnéticos”, disse Matt Shultz da Universidade de Queen no Canadá, e o principal autor do artigo aceito para publicação no Monthly Notices of the Royal Astronomical Society e que descreve a descoberta.
The abundance of_x_shaped_radio_sources_vla_survey_of_52_sources_with_off_axi...Sérgio Sacani
This document summarizes a study of 52 radio sources identified as candidate X-shaped radio galaxies from a previous survey. Higher resolution radio images were made of these sources using archival VLA data. The images reveal that:
- 60% of sources are actually double radio galaxies with twin lobes that have off-axis extensions, usually with inversion symmetry.
- At most 20% appear to be genuinely X-shaped with independent transverse features centered on the host galaxy.
- The remaining 20% do not fall clearly into the above categories.
- Optical identifications of host galaxies were made for most sources using SDSS and DSS images.
New m embers_of_the_tw_hydrae_association_and_two_accreting_m_dwarfs_in_scorp...Sérgio Sacani
Uma descoberta acidental de uma coleção de jovens estrelas do tipo anãs vermelhas perto do nosso Sistema Solar, poderiam nos dar uma rara ideia da formação planetária em câmera lenta. Os astrônomos da The Australian National University a ANU e a University of New South Wales, a UNSW, em Canberra, descobriram grandes discos de poeira ao redor de duas estrelas, mostrando sinais de planetas em processo de formação.
“Nós achamos que a Terra e todos os planetas se formaram de discos como esses, assim é fascinante ver um potencial novo sistema solar se formando”, disse o principal pesquisador Dr. Simon Murphy, da ANU Research School of Astronomy and Astrophysics.
“Contudo, outras estrelas dessa idade normalmente não têm mais discos. Os discos das anãs vermelhas parecem viver mais do que os de estrelas mais quentes como o Sol. Nós não entendemos por que”, disse o Dr. Murphy.
Radio continum emission_of_35_edge_on_galaxies_observed_with_the_vlaSérgio Sacani
Usando um dos maiores rádio observatórios do mundo, o Very Large Array do National Radio Astronomy, um grupo de astrônomos descobriram que os halos ao redor dos discos das galáxias espirais são muito mais comuns do que se pensava anteriormente.
A equipe, dirigida pela Dra. Judith Irwin, da Universidade de Queens, em Kingston, ON, Canadá, observou 35 galáxias espirais próximas de lado, de 11 a 137 milhões de anos-luz de distância da Terra.
As galáxias espirais, como a nossa própria Via Láctea ou a famosa Galáxia de Andrômeda, possuem uma vasta maioria de suas estrelas, gás, e poeira num disco plano em rotação com braços espirais. A maior parte da luz e das ondas de rádio observadas com telescópios veem de objetos localizados nesse disco.
“Nós sabíamos antes que alguns halos existiam, mas, usando o poder total do VLA atualizado e o poder total de algumas técnicas de processamento de imagens, nós descobrimos que esses halos são muito mais comuns entre as galáxias espirais do que nós pensávamos antes”, explicou a Dra. Irwin.
Flaring from the_supermassive_black_hole_in_mrk335_studied_with_swift_and_nustarSérgio Sacani
Os comportamentos estranhos e desconcertantes dos buracos negros tornam-se cada dia menos misteriosos, com as novas observações feitas com as missões Swift e NuSTAR da NASA. Os dois telescópios espaciais registraram um buraco negro supermassivo no meio de uma gigantesca explosão de luz de raio-X, ajudando os astrônomos a tentarem resolver um grande quebra-cabeça: Como os buracos negros supermassivos emitem flares?
Os resultados sugerem que os buracos negros supermassivos emitem flares de raios-X, quando suas coroas circundantes, fontes de partículas extremamente energéticas, são atiradas ou lançadas para fora dos buracos negros.
“Essa é a primeira vez que nós somos capazes de linkar o lançamento da coroa com uma flare”, disse Dan Wilkins, da Universidade de Saint Mary em Halifax, no Canadá e principal autor do artigo que descreve os resultados na revista Monthly Notices of The Royal Astronomical Society. “Isso nos ajudará a entender como os buracos negros supermassivos alimentam alguns dos objetos mais brilhantes do universo”.
Os buracos negros supermassivos não emitem luz por si só, mas eles as vezes são circundados por discos de material quente e brilhante. A gravidade do buraco negro puxa o gás ao redor, aquecendo esse material e fazendo com que ele brilhe com diferentes tipos de luz. Outra fonte da radiação perto do buraco negro é a coroa. As coroas são feitas de partículas altamente energéticas que geram luz de raio-X, mas os detalhes sobre sua aparência, ou como elas se formam, ainda não são claros.
3d modeling of_gj1214b_atmosphere_formation_of_inhomogeneous_high_cloouds_and...Sérgio Sacani
Uma equipe de cientistas da Universidade de Washington e da Universidade de Toronto foram os primeiros a simular nuvens exóticas em 3D na atmosfera de um exoplaneta.
O objeto em questão, é o GJ 1214b, um exoplaneta chamado de mini-Netuno que foi descoberto, seis anos atrás pelos astrônomos no Harvard-Smithsonian Center for Astrophysics.
Também conhecido como Gliese 1214b, esse mundo tem cerca de 2.7 vezes o diâmetro da Terra e uma massa quase 7 vezes maior que a massa do nosso planeta. Ele está localizado a cerca de 52 anos-luz de distância na constelação de Ophiuchus.
O planeta orbita a estrela anã vermelha, GJ 1214, a cada 38 horas, a uma distância de 1.3 milhões de milhas.
De acordo com estudos prévios, o planeta tem uma atmosfera rica em água ou hidrogênio com extensas nuvens.
“Deve existir altas nuvens ou uma névoa orgânica na atmosfera – como nós observamos em Titã. Sua temperatura atmosférica excede o ponto de fusão da água”, disse o Dr. Benjamin Charnay, um dos membros da equipe da Universidade de Washington.
First discovery of_a_magnetic_field_in_a_main_sequence_delta_scuti_star_the_k...Sérgio Sacani
Coralie Neiner do Laboratory for Space Studies and Astrophysics Instrumentation, LESIA (CNRS/Observatoire de Paris/UPMC/Université Paris Diderot) e Patricia Lampens (Royual OIbservatory of Belgium), descobriram a primeira estrela magnética do tipo delta Scuti, através de observações espectropolarimétricas, realizadas com o telescópio CFHT. As estrelas do tipo delta Scuti, são estrelas pulsantes, sendo que algumas delas mostram assinaturas atribuídas para um segundo tipo de pulsação. A descoberta mostra que isso é na verdade a assinatura de um campo magnético. Essa descoberta tem importantes implicações para o entendimento do interior das estrelas.
Dois tipos de estrelas pulsantes existem entre as estrelas com massa entre 1.5 e 2.5 vezes a massa do Sol: as estrelas do tipo delta Scuti e as estrelas do tipo gamma Dor. A teoria nos diz que as estrelas com temperatura entre 6900 e 7400 graus Kelvin podem ter ambos os tipos de pulsação. Essas são então chamadas de estrelas híbridas. Contudo, o satélite Kepler da NASA tem detectado um grande número de estrelas híbridas com temperaturas maiores ou menores do que esse limite pensado anteriormente. A existência dessas estrelas híbridas com temperaturas maiores é algo muito controverso, já que desafia o nosso entendimento sobre as estrelas pulsantes do tipo delta Scuti e gamma Dor.
The vvv survey_reveals_classical_cepheids_tracing_a_young_and_thin_stellar_di...Sérgio Sacani
Com o auxílio do telescópio VISTA instalado no Observatório do Paranal do ESO, astrônomos descobriram uma componente anteriormente desconhecida da Via Láctea. Ao mapear a localização de uma classe de estrelas que variam em brilho chamadas Cefeidas, foi descoberto um disco de estrelas jovens enterradas por trás de espessas nuvens de poeira no bojo central.
O rastreio público do ESO VISTA Variables in the Vía Láctea (VVV) [1] usa o telescópio VISTA instalado no Observatório do Paranal para obter imagens múltiplas em épocas diferentes das regiões centrais da nossa Galáxia nos comprimentos de onda do infravermelho [2]. O rastreio está descobrindo uma enorme quantidade de novos objetos, incluindo estrelas variáveis, aglomerados e estrelas em explosão (eso1101, eso1128, eso1141).
Uma equipe de astrônomos, liderada por Istvan Dékány da Pontificia Universidad Católica de Chile, utilizou dados deste rastreio, obtidos entre 2010 e 2014, para fazer uma descoberta notável — um componente anteriormente desconhecido da Via Láctea, a Galáxia que nos acolhe.
On the theory_and_future_cosmic_planet_formationSérgio Sacani
A Terra chegou cedo para a festa no universo em evolução. De acordo com um novo estudo teórico, quando o nosso Sistema Solar nasceu a 4.6 bilhões de anos atrás, somente 8% dos planetas possivelmente habitáveis que serão formados no universo, existiam. E, a festa não terminaria até quando o Sol queimasse por outros 6 bilhões de anos. A totalidade desses planetas, 92%, não tinham nascido.
Essa conclusão é baseada no acesso dos dados coletados pelo Telescópio Espacial Hubble da NASA e o prolífico caçador de exoplanetas, o Observatório Espacial Kepler.
“Nossa principal motivação foi entender o lugar da Terra no contexto do resto do universo”, disse o autor do estudo Peter Behroozi do Space Telescope Science Institute (STScI), em Baltimore, Maryland, “Comparado a todos os planetas que irão se formar no universo, a Terra, na verdade chegou cedo”.
Olhando distante no espaço e no tempo, o Hubble, tem dado aos astrônomos um verdadeiro “álbum de família”, das observações da galáxia que mostra a história da formação do universo à medida que as galáxias cresciam. Os dados mostram que o universo estava gerando estrelas numa taxa elevada a 10 bilhões de anos atrás, mas a fração do gás hidrogênio e hélio do universo que estava envolvida era muito baixa. Hoje, o nascimento de estrelas está acontecendo numa taxa muito mais lenta do que a muito tempo atrás, mas existe muito gás deixado para trás disponível que o universo continuará gerando estrelas e planetas por muito tempo ainda.
A precise water_abundance_measurement_for_the_hot_jupiter_wasp_43bSérgio Sacani
This document presents a precise measurement of the water abundance in the atmosphere of the exoplanet WASP-43b using transmission and thermal emission spectroscopy from the Hubble Space Telescope. The key findings are:
1) The water content of WASP-43b's atmosphere is consistent with solar composition at planetary temperatures, ranging from 0.4 to 3.5 times the solar water abundance.
2) This metallicity measurement extends the trend seen in the solar system of lower metal enrichment for higher mass planets.
3) Measuring a planet's water content constrains its formation location in the protoplanetary disk and provides insight into planetary formation models.
This document presents an analysis of transit spectroscopy observations of three exoplanets - WASP-12 b, WASP-17 b, and WASP-19 b - using the Wide Field Camera 3 instrument on the Hubble Space Telescope. The observations achieved almost photon-limited precision but uncertainties in the transit depths were increased by the uneven sampling of the light curves. The final transit spectra for all three planets are consistent with the presence of a water absorption feature at 1.4 microns, though the amplitude is smaller than expected from previous Spitzer observations possibly due to hazes. Due to degeneracies between models, the data cannot unambiguously constrain the atmospheric compositions without additional observations.
High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019Sérgio Sacani
Imaging observations of Jupiter with high spatial resolution were acquired beginning in 2016, with a cadence of 53
days to coincide with atmospheric observations of the Juno spacecraft during each perijove pass. The Wide Field
Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) collected Jupiter images from 236 to 925 nm in 14
filters. The Near-Infrared Imager (NIRI) at Gemini North imaged Jovian thermal emission using a lucky-imaging
approach (co-adding the sharpest frames taken from a sequence of short exposures), using the M′ filter at 4.7 μm.
We discuss the data acquisition and processing and an archive collection that contains the processed WFC3 and
NIRI data (doi:10.17909/T94T1H). Zonal winds remain steady over time at most latitudes, but significant
evolution of the wind profile near 24°N in 2016 and near 15°S in 2017 was linked with convective superstorm
eruptions. Persistent mesoscale waves were seen throughout the 2016–2019 period. We link groups of lightning
flashes observed by the Juno team with water clouds in a large convective plume near 15°S and in cyclones near
35°N–55°N. Thermal infrared maps at the 10.8 micron wavelength obtained at the Very Large Telescope show
consistent high brightness temperature anomalies, despite a diversity of aerosol properties seen in the HST data.
Both WFC3 and NIRI imaging reveal depleted aerosols consistent with downwelling around the periphery of the
15°S storm, which was also observed by the Atacama Large Millimeter/submillimeter Array. NIRI imaging of
the Great Red Spot shows that locally reduced cloud opacity is responsible for dark features within the vortex. The
HST data maps multiple concentric polar hoods of high-latitude hazes.
The deep blue_color_of_hd189733b_albedo_measurements_with_hst_stis_at_visible...Sérgio Sacani
The document summarizes a study that measured the geometric albedo of the exoplanet HD 189733b across visible wavelengths using Hubble Space Telescope observations. It found an albedo of 0.40 ± 0.12 at 290-450 nm that decreased to below 0.12 at 450-570 nm, suggesting optically thick clouds reflecting light at shorter wavelengths and sodium absorption suppressing reflection beyond 450 nm. This wavelength-dependent albedo implies HD 189733b would appear deep blue in color at visible wavelengths.
The document summarizes observations of water in Jupiter's stratosphere made by the Herschel Space Observatory. Herschel/HIFI obtained a 5x5 pixel map of a water emission line, finding that water decreases from southern to northern latitudes. Herschel/PACS also obtained water maps. Infrared Telescope Facility observations of methane were used to constrain stratospheric temperatures. The latitudinal distribution of water cannot be explained by temperature variations and rules out interplanetary dust as the main water source. The observations provide evidence that Jupiter's stratospheric water originated from the 1994 Shoemaker-Levy 9 comet impacts.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
Mapping the Skies of Ultracool Worlds: Detecting Storms and Spots with Extrem...Sérgio Sacani
Extremely large telescopes (ELTs) present an unparalleled opportunity to study the magnetism,
atmospheric dynamics, and chemistry of very low mass stars (VLMs), brown dwarfs, and exoplanets.
Instruments such as the Giant Magellan Telescope - Consortium Large Earth Finder (GMT/GCLEF),
the Thirty Meter Telescope’s Multi-Objective Diffraction-limited High-Resolution Infrared Spectrograph
(TMT/MODHIS), and the European Southern Observatory’s Mid-Infrared ELT Imager and Spectrograph (ELT/METIS) provide the spectral resolution and signal-to-noise (S/N) necessary to Doppler
image ultracool targets’surfaces based on temporal spectral variations due to surface inhomogeneities.
Using our publicly-available code, Imber, developed and validated in Plummer & Wang (2022), we
evaluate these instruments’abilities to discern magnetic star spots and cloud systems on a VLM star
(TRAPPIST-1); two L/T transition ultracool dwarfs (VHS J1256−1257 b and SIMP J0136+0933); and
three exoplanets (Beta Pic b and HR 8799 d and e). We find that TMT/MODHIS and ELT/METIS are
suitable for Doppler imaging the ultracool dwarfs and Beta Pic b over a single rotation. Uncertainties
for longitude and radius are typically . 10◦
, and latitude uncertainties range from ∼ 10◦
to 30◦
.
TRAPPIST-1’s edge-on inclination and low υ sin i provide a challenge for all three instruments while
GMT/GCLEF and the HR 8799 planets may require observations over multiple rotations. We compare
the spectroscopic technique, photometry-only inference, and the combination of the two. We find
combining spectroscopic and photometric observations can lead to improved Bayesian inference of
surface inhomogeneities and offers insight into whether ultracool atmospheres are dominated by spotted
or banded features.
The pristine nature of SMSS 1605−1443 revealed by ESPRESSOSérgio Sacani
SMSS J160540.18−144323.1 is the carbon-enhanced metal-poor (CEMP) star with the lowest iron abundance ever measured, [Fe/H] =
−6.2, which was first reported with the SkyMapper telescope. The carbon abundance is A(C) ≈ 6.1 in the low-C band, as the majority of the stars
in this metallicity range. Yet, constraining the isotopic ratio of key species, such as carbon, sheds light on the properties and origin of these elusive
stars.
Aims. We performed high-resolution observations of SMSS 1605−1443 with the ESPRESSO spectrograph to look for variations in the radial
velocity (vrad) with time. These data have been combined with older MIKE and UVES archival observations to enlarge the temporal baseline. The
12C/
13C isotopic ratio is also studied to explore the possibility of mass transfer from a binary companion.
Methods. A cross-correlation function against a natural template was applied to detect vrad variability and a spectral synthesis technique was used
to derive 12C/
13C in the stellar atmosphere.
Results. We confirm previous indications of binarity in SMSS 1605−1443 and measured a lower limit 12C/
13C > 60 at more than a 3σ confidence
level, proving that this system is chemically unmixed and that no mass transfer from the unseen companion has happened so far. Thus, we confirm
the CEMP-no nature of SMSS 1605−1443 and show that the pristine chemical composition of the cloud from which it formed is currently imprinted
in its stellar atmosphere free of contamination.
Astronomy from the Moon: From Exoplanets to Cosmology and Beyond in Visible L...Sérgio Sacani
We review what could be astronomy from the Moon in the next decades in the visible domain.
After a short review observational approaches, from photometry to high contrast and high angular
resolution imaging, We essentially focus on some promising scientific objectives, from Solar
System to the extragalactic domain. At the end, I add a proposal to use the Earth-Moon system to
test fundamental physics. Since this meeting is dedicated to the next decades of Astronomy from
the Moon, we consider projects and science objectives for several decades from now.
1) This study uses a deep learning model to estimate stratospheric gravity wave potential energy (GW Ep) averaged over 20-30 km using ERA5 reanalysis data and terrain data as inputs. The model is trained using GW Ep values calculated from COSMIC radio occultation data as labels.
2) The results show the model can effectively estimate the zonal trend of GW Ep but with larger errors in low latitudes than mid-latitudes. Seasonal variations are also seen in the estimated GW Ep.
3) The estimated GW Ep shows the effect of the quasi-biennial oscillation, though its amplitude may be less than that of the measured GW Ep from COSMIC data.
This document summarizes the results of infrared transmission spectroscopy of the exoplanets HD 209458b and XO-1b using the Hubble Space Telescope's Wide Field Camera 3 instrument. Key findings include:
- Both planets exhibited water absorption of approximately 200 ppm at the peak water absorption wavelength of 1.38 microns.
- The water absorption measured for XO-1b contradicts stronger absorption reported from previous observations using a different instrument.
- The weak water absorption measured for HD 209458b is consistent with previous observations of weak molecular absorption features for this planet.
- Model atmospheres including uniformly distributed extra opacity can approximately account for the water measurements as well as previous sodium absorption measurements for
This summary provides the key details from the document in 3 sentences:
Galactic winds play an important role in galaxy evolution but are difficult to detect, so the document describes developing a novel graphical user interface method to detect wind emissions in distant galaxy spectra from surveys like DEEP2 and DEEP3. The interface allows for efficient inspection of individual galaxy spectra to remove errors before stacking, and determines distances to emission lines through Gaussian fitting or 1D collapsing to measure wind extent. No extended wind emissions were found in either survey using this new procedure.
- Astrônomos descobriram que uma pequena estrela, do tamanho de Júpiter, possui uma tempestade muito parecida com a Grande Mancha Vermelha e que está ali, persistente por dois anos.
- Enquanto nos planetas, esse tipo de característica é normal, em estrelas essa é a melhor evidência encontrada até hoje.
- A estrela é chamada de W1906+40 e pertence a uma classe de objetos frios chamados de Anãs-L.
- Elas são consideradas estrelas pois fundem átomos e geram luz, como o Sol faz, enquanto que as anãs marrons são conhecidas como estrelas que falharam, pois elas não possuem o processo de fusão atômica em seu interior.
- Nesse novo estudo os astrônomos foram capazes de verificar as mudanças na atmosfera da estrela por dois anos. A técnica usada foi semelhante à de detecção de exoplanetas, analisando a curva de luz da estrela, que apresentava quedas, mas que não era por questão de planetas.
- Os astrônomos usaram o Spitzer e estudaram a luz infravermelha da estrela, que revelou uma gigantesca mancha escura que não era uma mancha magnética estelar, mas sim uma tempestade com um diâmetro equivalente ao de 3 Terras. O spitzer foi capaz de estudar camadas diferentes da atmosfera da estrela e esses dados junto com os dados do Kepler, revelaram com clareza a tempestade estelar.
- Futuras observações serão realizadas usando os dois equipamentos para tentar identificar esse tipo de tempestade em anãs marrons, por exemplo, e tentar descobrir se esse tipo de fenômeno é muito comum, ou é raro no universo.
The extremely high albedo of LTT 9779 b revealed by CHEOPSSérgio Sacani
Optical secondary eclipse measurements of small planets can provide a wealth of information about the reflective properties
of these worlds, but the measurements are particularly challenging to attain because of their relatively shallow depth. If such signals
can be detected and modeled, however, they can provide planetary albedos, thermal characteristics, and information on absorbers in
the upper atmosphere.
Aims. We aim to detect and characterize the optical secondary eclipse of the planet LTT 9779 b using the CHaracterising ExOPlanet
Satellite (CHEOPS) to measure the planetary albedo and search for the signature of atmospheric condensates.
Methods. We observed ten secondary eclipses of the planet with CHEOPS. We carefully analyzed and detrended the light curves using
three independent methods to perform the final astrophysical detrending and eclipse model fitting of the individual and combined light
curves.
Results. Each of our analysis methods yielded statistically similar results, providing a robust detection of the eclipse of LTT 9779 b
with a depth of 115±24 ppm. This surprisingly large depth provides a geometric albedo for the planet of 0.80+0.10
−0.17, consistent with
estimates of radiative-convective models. This value is similar to that of Venus in our own Solar System. When combining the eclipse
from CHEOPS with the measurements from TESS and Spitzer, our global climate models indicate that LTT 9779 b likely has a super
metal-rich atmosphere, with a lower limit of 400× solar being found, and the presence of silicate clouds. The observations also reveal
hints of optical eclipse depth variability, but these have yet to be confirmed.
Conclusions. The results found here in the optical when combined with those in the near-infrared provide the first steps toward
understanding the atmospheric structure and physical processes of ultrahot Neptune worlds that inhabit the Neptune desert.
The Variable Detection of Atmospheric Escape around the Young, Hot Neptune AU...Sérgio Sacani
This document summarizes observations from the Hubble Space Telescope of the young hot Neptune exoplanet AU Mic b, which orbits the nearby M dwarf star AU Mic. The observations aimed to detect atmospheric escape of neutral hydrogen through absorption in the stellar Lyman-alpha emission line. Two visits were obtained, one in 2020 and one in 2021, corresponding to transits of the planet. A stellar flare was observed and removed from the first visit data. In the second visit, absorption was detected in the blue wing of the Lyman-alpha line 2.5 hours before the white light transit, indicating the presence of high-velocity neutral hydrogen escaping the planet's atmosphere and traveling toward the observer. Estimates place the column density of this material
Herschel galactic plane_survey_the_global_distribution_of_ism_gas_componnentSérgio Sacani
This document summarizes a study using Herschel observations of the [C ii] 158μm line to analyze the distribution of different gas components in the Milky Way galaxy. The observations provide high-resolution maps of [C ii] emission across the Galactic plane. By comparing these maps to observations of HI, CO, and other tracers, the study finds that [C ii] emission is associated with spiral arms between 4-10 kpc from the Galactic center. It estimates that [C ii] traces dense photon-dominated regions (47%), CO-dark H2 gas (28%), cold atomic gas (21%), and ionized gas (4%). The study also analyzes the distribution of cold neutral medium versus
This document summarizes a blind HI survey of the southern Milky Way zone of avoidance conducted with the Parkes radio telescope. The survey detected 883 galaxies at Galactic longitudes 212° < l < 36° and latitudes |b| < 5° to a sensitivity of 6 mJy per 27 km/s channel. Fifty-one percent of detections had known optical/near-infrared counterparts, while 27% had new counterparts identified. The survey delineated large-scale structures in the Puppis and Great Attractor regions for the first time. Several newly identified galaxy concentrations and clusters were revealed that help trace the Great Attractor Wall.
EUV fine structure and variability associated with coronal rain revealed by S...Sérgio Sacani
Coronal rain is the most dramatic cooling phenomenon of the solar corona. Recent observations in the visible and UV
spectrum have shown that coronal rain is a pervasive phenomenon in active regions. Its strong link with coronal heating through the
Thermal Non-Equilibrium (TNE) - Thermal Instability (TI) scenario, makes it an essential diagnostic tool for the heating properties.
Another puzzling feature of the solar corona, besides the heating, is its filamentary structure and variability, particularly in the EUV.
Aims. We aim to identify observable features of the TNE-TI scenario underlying coronal rain at small and large spatial scales, to
understand the role it plays in the solar corona.
Methods. We use EUV datasets at unprecedented spatial resolution of ≈ 240 km from the High Resolution Imager (HRI) in the EUV
(HRIEUV) of the Extreme Ultraviolet Imager (EUI) and SPICE on board Solar Orbiter from the spring 2022 perihelion.
Results. EUV absorption features produced by coronal rain are detected at scales as small as 260 km. As the rain falls, heating
and compression is produced immediately downstream, leading to a small EUV brightening accompanying the fall and producing
a ‘fireball’ phenomenon in the solar corona. Just prior to impact, a flash-like EUV brightening downstream of the rain, lasting a
few minutes is observed for the fastest events. For the first time, we detect the atmospheric response to the rain’s impact on the
chromosphere and consists of upward propagating rebound shocks and flows partly reheating the loop. The observed widths of the
rain clumps are 500 ± 200 km. They exhibit a broad velocity distribution of 10 − 150 km s−1
, peaking below 50 km s−1
. Coronal
strands of similar widths are observed along the same loops co-spatial with cool filamentary structure seen with SPICE, which we
interpret as the Condensation Corona Transition Region. Matching with the expected cooling, prior to the rain appearance sequential
loop brightenings are detected in gradually cooler lines from corona to chromospheric temperatures. Despite the large rain showers,
most cannot be detected in AIA 171 in quadrature, indicating that line-of-sight effects play a major role in coronal rain visibility. Still,
AIA 304 and SPICE observations reveal that only a small fraction of the rain can be captured by HRIEUV.
Conclusions. Coronal rain generates EUV structure and variability over a wide range of scales, from coronal loop to the smallest
resolvable scales. This establishes the major role that TNE-TI plays in the observed EUV morphology and variability of the corona.
An Earth-sized exoplanet with a Mercury-like compositionSérgio Sacani
Earth, Venus, Mars and some extrasolar terrestrial planets1
have a mass and radius that is consistent with a mass fraction
of about 30% metallic core and 70% silicate mantle2
. At the
inner frontier of the Solar System, Mercury has a completely
different composition, with a mass fraction of about 70%
metallic core and 30% silicate mantle3
. Several formation or
evolution scenarios are proposed to explain this metal-rich
composition, such as a giant impact4, mantle evaporation5
or the depletion of silicate at the inner edge of the protoplanetary
disk6. These scenarios are still strongly debated.
Here, we report the discovery of a multiple transiting planetary
system (K2-229) in which the inner planet has a radius
of 1.165 ± 0.066 Earth radii and a mass of 2.59 ± 0.43 Earth
masses. This Earth-sized planet thus has a core-mass fraction
that is compatible with that of Mercury, although it was
expected to be similar to that of Earth based on host-star
chemistry7
. This larger Mercury analogue either formed with
a very peculiar composition or has evolved, for example, by
losing part of its mantle. Further characterization of Mercurylike
exoplanets such as K2-229 b will help to put the detailed
in situ observations of Mercury (with MESSENGER and
BepiColombo8) into the global context of the formation and
evolution of solar and extrasolar terrestrial planets.
Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanetGOASA
1) The transmission spectrum of the exoplanet HAT-P-11b was observed using Hubble and Spitzer space telescopes.
2) Water vapor absorption was detected at 1.4 micrometers in the atmosphere, indicating a clear atmosphere down to 1 mbar pressure.
3) The detection of water vapor and relatively large atmospheric scale height places an upper limit on the abundance of heavy elements in the atmosphere of around 700 times the solar value, consistent with core accretion planet formation theories.
Similar to First results from_the_hubble_opal_program_jupiter_in_2015 (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Travis Hills' Endeavors in Minnesota: Fostering Environmental and Economic Pr...Travis Hills MN
Travis Hills of Minnesota developed a method to convert waste into high-value dry fertilizer, significantly enriching soil quality. By providing farmers with a valuable resource derived from waste, Travis Hills helps enhance farm profitability while promoting environmental stewardship. Travis Hills' sustainable practices lead to cost savings and increased revenue for farmers by improving resource efficiency and reducing waste.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
2. >650 nm (Wong 2010). Standard flatfield corrections remove
fringing error when the targetʼs spectral energy distribution is
the same as the continuum spectrum of the calibration lamps
used to construct the flatfields themselves. However, Jupiterʼs
spectrum is different, particularly near methane absorption
bands, requiring additional correction. Our FQ889N images
were corrected by about 2%, using preliminary fringing
flatfields (Wong 2011) generated using the disk-averaged
reflectance spectrum of Jupiter (Karkoschka 1998) convolved
with the solar spectrum (Colina et al. 1996).
After corrections, each image was navigated to find the
planet center using iterative ellipsoid limb fitting with Jupiterʼs
known radii and geocentric distance and assigned proper sub-
Earth and sub-solar latitude and longitude. Navigated images
were then adjusted for limb darkening using a Minnaert
approximation (ratio of the cosines of the incident and emission
angles raised to the k power) with the k coefficients listed in
Table 1, and projected onto planetographic cylindrical maps.
These maps were then mosaicked in each wavelength, except
F467M, which was saturated, to produce global maps for
further analysis, Figures 1(a) and (b). These maps are publicly
available at https://archive.stsci.edu/prepds/opal/.
3. ANALYSES AND RESULTS
3.1. Zonal Wind Field
Jupiterʼs zonal wind profile is known to be relatively stable
with time, with only small (10–20 m s−1
) variations at some
wind jet peaks (Limaye 1989; Simon-Miller & Gierasch 2010;
Asay-Davis et al. 2011). The OPAL data set will allow for the
retrieval of a full two-dimensional wind field, requiring
iterative automated retrievals to generate sufficient density of
wind vectors. However, a quick comparison of the zonal wind
field can be performed with a simple cross-correlation between
the two global maps. Figure 2 shows such a correlation,
computed from 360° of longitude and at every 0°.1 of latitude,
using the global maps in the F631N filter; the retrieved zonal
wind is plotted at the displacement with maximum correlation
(solid black line). While the profile retrieval can be further
refined, the preliminary result shows very good agreement with
both the Cassini (blue line, Porco et al. 2003) and Voyager (red
line, Simon-Miller & Gierasch 2010) zonal wind profiles.
Manual measurements (plus symbols) indicate that the changes
in the zonal jets, compared with Voyager and Cassini are real.
Notably, the peak of the 24° N jet is at about 153 m s−1
,
between the Cassini and Voyager values of 138 and 184 m s−1
,
respectively. Other jets’ differences are due, in part, to
differences in the presence of features with distinct drift rates
in the different epochs. For example, near 7° S, the Hubble data
show a higher zonal average, but the large South Equatorial
disturbance, visible during Voyager and again during Cassini
was not present in 2015; it moves more slowly that the zonal
wind, and may be related to large wave phenomena (Beebe
et al. 1989; Simon-Miller et al. 2012). Changes in other jets
require a more detailed analysis of the cloud features, retrieval
of the full 2D wind circulation, and masking of vortices and
other discrete features with distinct drift rates (e.g., Asay-Davis
et al. 2011; Barrado-Izagirre et al. 2013), efforts that are
beyond the scope of this initial report.
3.2. Spectral Comparisons
As the map in Figure 1 shows, many red features are visible
for spectral analysis. The Great Red Spot (GRS) still appears
very orange, as it did in 2014 (Simon et al. 2014). Oval BA, to
its southeast, is somewhat paler, with a whitish core and fainter
orange annulus. The North Equatorial Belt (NEB) and cyclonic
barges in the northern hemisphere remain the visibly reddest
features on the planet (Sanchez-Lavega et al. 2013; Simon et al.
2015b). Filters in the OPAL program were specifically chosen
to allow comparison of the spectral characteristics of these
features with previous data sets. Figure 3 shows the 2015
OPAL data (red symbols) of the core of the GRS and reddest
regions of the NEB with other data sets from 1995 to 2014.
Note that the F467M filter was saturated across much of the
planet, but red regions far from the saturation were usable.
The overall UV to green absorption in the GRS remains
consistent with measurements from 2014, though the 889-nm
methane absorption band brightness has returned to its pre-
Table 1
OPAL Data Acquired
Rotation 1 (2015 January 19 02:00 to 12:30 UT)
Filter Minnaert k Notes Analyses
F631N .999 L Spectral,
Winds
F502N .950 L Spectral,
Waves
F395N .850 L Spectral,
Waves
F467M n/a Saturated Spectral
FQ889N 1.00 Slight saturation in GRS core in
10:28 UT frame, corrected for
fringing
Spectral,
Waves
F658N .999 L Spectral
F275W n/a L Spectral,
Waves
F547M .970 Slight saturation near the equator Spectral
Rotation 2 (2015 January 19 15:00 to 23:40 UT)
Filter Minnaert k Notes Analyses
F631N .999 L Spectral,
Winds
F502N .950 L Spectral,
Waves
F395N .850 L Spectral,
Waves
F467M n/a Saturated Spectral
FQ889N 1.00 Corrected for fringing Spectral,
Waves
F658N .999 L Spectral
F275W n/a L Spectral,
Waves
F343N .850 L Spectral
2
The Astrophysical Journal, 812:55 (8pp), 2015 October 10 Simon, Wong, & Orton
3. 2014 value, indicating less haze reflectivity compared with
2014. The evolution of the GRS—a color change coincident
with increased haze reflectivity, followed by a decrease in haze
but constant color—is distinctly different from the evolution of
other Oval BA (the smaller red storm to the south and east in
Figure 1), where a one time color change occurred along with
no change in haze reflectivity (Wong et al. 2011). These details
may prove important in determining the identity and control-
ling processes of red chromophores on Jupiter, as well as the
evolution of large anticyclones. The NEB spectrum remains
nearly constant at all wavelengths.
3.3. GRS Properties
Hubble data in 2014 confirmed that the GRSʼs longitudinal
width has decresed significantly since 2012 (Simon
et al. 2014). In 2015 it spanned 13°.9 of longitude and 9°.7 of
latitude. This represents a return to the normal longitude
shrinkage rate of ∼0°.19/year, while the latitude extent
increased slightly over the 2014 measurements. It is currently
centered near 22°.4 S latitude, and its color indicates that there
is still decreased interaction with the nearby zonal wind jets
(Simon et al. 2014). The time resolution of the Hubble
observations are not sufficient to determine whether the
Figure 1. Jupiter global map from Hubble OPAL data, Rotation 1. Images are mapped between 79°.9 N and 79°.9 S latitude at 0°.1/pixel resolution and color is
constructed from red = 631, green = 502, and blue = 395-nm maps, respectively. (b) The same as Figure 1(a), from Rotation 2.
3
The Astrophysical Journal, 812:55 (8pp), 2015 October 10 Simon, Wong, & Orton
4. observed size/shape changes have any periodic components
analogous to oscillations seen by Voyager in Neptuneʼs Great
Dark Spot (Smith et al. 1989; LeBeau & Dowling 1998).
An interesting feature in the 2015 data, however, is the
internal GRS appearance. The core region, usually the most
prominent at violet wavelengths, has been gradually shrinking,
concurrent with its overall size changes (see Simon-Miller et al.
2002, Figure 3). By 2014, this separate core was largely absent
(Simon et al. 2014), and, in 2015, filamentary structures can be
seen spiralling near the core, Figure 4. Over 10 hours, the
motion in this structure is apparent. It was not possible to
retrieve a detailed velocity field in 2014, due to Ganymedeʼs
shadow in the region, but the velocities that were measured
were consistent with previous measurements. Preliminary
manual measurements confirm velocities in the range of
100–150 m s−1
, as expected, but the OPAL data will enable
later detailed flow field mapping.
3.4. Baroclinic Instability and Waves
The OPAL data also show a feature not previously observed
in Hubble images, a small-scale wave in the NEB, see Figures 5
and 6. These fine-scale waves reside in the cyclonic region of
the wind field, below several anticyclones to the north and at
the same latitudes as a series of small cyclonic cells, as denoted
in Figure 5. They are visible in both global maps, and at all
continuum wavelengths from 343 to 658 nm; they may be
visible at 275 and 889-nm, though at very low contrast levels.
The features have a wavelength of about 1° (1200 km), larger
than the 300 km mesoscale waves seen in Voyager and New
Horizons data (Hunt & Muller 1979; Reuter et al. 2007; Simon
et al. 2015a).
As shown in Figure 6, these waves span ∼2°–3° of latitude
covering the cyclonic flank of the westward jet that peaks at
17° N. Although the wave is visible in multiple images, it is
difficult to identify the same wave crests from frame to frame in
large time separations, even in the filter with best contrast,
F395N, Figure 6 middle and bottom panels. Wave crest
identification is not unique over a 20-hr separation and no
detectable wave motions were possible. Short 1-hr time
separations are too short to confirm velocities, given the large
velocity uncertainties over such a short time period at the
available spatial resolution.
Figure 2. Hubble wind profile found from cross-correlation of the maps in
Figure 1. The blue line is the Cassini profile in late 2000 (Porco et al. 2003) and
the red line is from Voyager in 1979 (Simon-Miller & Gierasch 2010). The new
wind profile matches previous profiles at most latitudes; manual measurement
checks of wind jet magnitude are shown by + symbols.
Figure 3. Reflectance spectra of the North Equatorial Belt and Great Red Spot from 1995 to 2015. The darkest spots of the NEB remain stable in color, while the GRS
retains the increased blue absorption seen in 2014.
4
The Astrophysical Journal, 812:55 (8pp), 2015 October 10 Simon, Wong, & Orton
5. This type of wave is similar in appearance to terrestrial wave
formation in a baroclinic instability (see Holton 1992, Figure 6.5).
On the Earth, baroclinic instabilities explain mid- to high-latitude
cyclone generation, and waves form along with cyclonic features
(Charney 1947; Eady 1949). On the giant planets, such instabilities
may play a role in wind jet formation (e.g., Kaspi & Flierl 2007).
Using the Earth analogy, we can examine the characteristics of the
OPAL wave for consistency with a baroclinic wave.
Figure 4. Jupiterʼs Great Red Spot in F395N (bottom) and F631N (top), with System III W. longitude and planetographic latitude labeled. The left panels are from the
first rotation, and the right panels are 10 hr later. Internal structures in the right panels have rotated counterclockwise relative to the left panels.
Figure 5. Limited longitude region centered on 16° N latitude. Small-scale waves are superimposed on other cloud structures in the North Equatorial Belt, including
cyclones at the same latitude. Anticyclones are visible to the north corresponding to the anticyclonic shear region of the background wind field.
5
The Astrophysical Journal, 812:55 (8pp), 2015 October 10 Simon, Wong, & Orton
6. One diagnostic is the meridional size of the wave features.
Stone (1969) showed that for most baroclinic waves, the
meridional scale should be on the order of the radius of
deformation. However, Simmons (1974) showed that if the jet
width scale is larger than the deformation radius, the waveʼs
meridional extent can be between the two in scale.
Gierasch et al. (1979) modeled Jupiterʼs atmosphere using a
nearly adiabatic deep layer beneath the clouds. Unlike the Eady
(1949) terrestrial model with a rigid lower boundary, this
scheme had drastically reduced growth rates of baroclinic
instabilities due to the influence of the deep neutrally stable
layer. Conrath et al. (1981) examined this again and found that
for westward jets that are broad (where the deformation scale is
much smaller than the jet width), the Eady modes are still
suppressed, but Charney modes (Charney 1947) are allowed
and the disturbance can be a mix of barotropic and baroclinic
instabilities if deformation radius and jet width are comparable.
The main difference between the Eady and Charney modes is
the influence of the gradient of the Coriolis parameter, which
makes Charney mode growth less dependent on the bottom
boundary condition. Conrath et al. (1981) hypothesized that the
jet widths in Jupiterʼs atmosphere, at least 3–10 times the
tropospheric deformation radius, would enable transfer of
energy from eddies to jets. Instabilities are baroclinic within
this range.
The atmospheric radius of deformation is defined as
L NH f ,∣ ∣=
where N is the Brunt–Vaisala frequency, H is the scale height,
and f is the Coriolis parameter. The Coriolis parameter, f, is
9.1 × 10−5
s−1
at 15° N planetographic latitude. The pressure
scale height, H = kB T/m g, is 25 km, using a temperature of
160 K (near the NH3 cloud base), an effective gravity of
Figure 6. Wave crest location and evolution. In the top panel, the Cassini wind profile is plotted over a color map, showing that the waves reside in the cyclonic shear
region. The middle and bottom panels show F395N maps 20 hr apart, showing that little wave evolution or motion has occurred.
6
The Astrophysical Journal, 812:55 (8pp), 2015 October 10 Simon, Wong, & Orton
7. 22.88 m s−2
for 15° latitude, and a mean molecular mass of
2.30 Da assuming Galileo Probe composition (Niemann
et al. 1998; Mahaffy et al. 2000; Wong et al. 2004). The
Brunt–Vaisala frequency, N, describes the static stability of the
atmosphere, and has been constrained by a number of methods
in Jupiterʼs atmosphere, including models of cloud formation
and vortex circulation, and temperature profiles measured by
radio occultations, infrared spectroscopy, and in situ measure-
ment by the Galileo Probe; typical values of N range from 2 to
12 × 10−3
s−1
in and between the cloud layers, to 1.6 and to
2.3 × 10−2
s−1
at 250 mbar just below the tropopause
(Wong 2011; Watkins & Cho 2013 and references therein).
The atmospheric deformation radius near the NH3 cloud base
is then around 1400 km if cloud condensation creates stability,
or 500 km in the free air below this cloud level. The wind
jet spans 4°.5 of latitude or ∼5000 km, just broad enough to
meet the minimum 3–10 L criterion for possible energy
transport from eddies to jets (Conrath et al. 1981). The waves
span 2000–3000 km, and are thus consistent with the Simmons
(1974) model of the meridional scale of baroclinic instabilities.
Additionally, on Earth, baroclinic instabilities tilt westward
and northward with altitude (e.g., Lim & Wallace 1991; Yin
& Battisti 2004). The Hubble images at 889 and 275 nm
are more sensitive to higher altitudes, but both have little
high contrast detail and also show underlying cloud structure,
so any such tilts are not obvious, see Figure 7. However, some
of the wave crests do have a slight westward tilt with the
zonal wind pattern, Figure 5, while others near the cyclone
at 202° W are curved. This is consistent with theoretical
models (Holton 1992) and Earth observations (e.g., Blackmon
et al. 1984).
4. DISCUSSION
One aspect that is unclear is the exact atmospheric conditions
needed for baroclinic wave formation on Jupiter. Waves of this
type have not been seen on other dates in Hubble imaging from
1994 to 2014 nor by the Galileo or Cassini spacecraft. The one
exception is during Voyager 2, where a similar, but very faint,
feature was briefly observed with 700–1000-km wavelength
at these latitudes (Smith et al. 1979, Figure 8). It was seen
10 hr later, and possibly after several days, but only over a
limited longitudinal region. However, during the Voyager 1
flyby several months earlier, and Hubble observations in
1994–1996, the region had similar anticyclone/cyclone
patterns and zonal wind magnitudes, and yet the wave structure
was not observed. Other concurrent atmospheric conditions,
such as temperature variations, must be necessary for wave
formation/visibility.
Baroclinic instabilities with ∼1200 km wavelength have
growth times of about 30 days and correspond to a Brunt–
Vaïsälä frequency of N = 0.0014 s−1
in the level where the
instability is seated, in the model of Conrath et al. (1981).
Conditions are therefore typical of the free air between major
cloud layers because N within cloud layers is significantly
greater, on the order of 0.005–0.01 s−1
(Wong 2011). This
presents an interesting problem: static stability must be weak,
calling for an altitude that is well separated vertically from the
cloud condensation layers. However, the wave must be
propagating at an altitude where clouds do condense, or else
there would be no visible wave tracers. This seeming
Figure 7. False color map of the wave region with red = 889 nm, green = 502 nm, and blue = 275-nm images. Wave shifts in altitude would be apparent as color
changes along or across a wave crest; none are apparent. The highest thick clouds are white/yellow deep clouds covered with haze/aerosol are blue, and red areas
indicate regions of high cloud but less haze.
Figure 8. Voyager 2 image centered near 16° N latitude. This image was acquired on 1979 July 3 in the violet filter and shows a faint wave train of a similar scale as
one as seen in the Hubble data. Note that this image is not shown at the same scale as the Hubble data.
7
The Astrophysical Journal, 812:55 (8pp), 2015 October 10 Simon, Wong, & Orton
8. contradiction may play a role in the apparent rarity of this type
of wave structure. We may be observing a disturbance that is
seated in a weakly stratified layer between cloud decks, but can
only be observed when it propagates vertically into a cloud
condensation level. Achterberg & Ingersoll (1989) emphasized
the sensitivity of baroclinic instabilities to stratification and
wind shear, suggesting that future numerical simulations may
further test the vertical profiles of temperature and horizontal
velocity needed to generate these features.
5. SUMMARY
The OPAL program has begun its yearly campaign of high-
resolution imaging of the outer planets. Jupiter data acquired in
2015 are already yielding new results, as well as adding to the
long-term monitoring of the atmospheric state. Within naviga-
tion uncertainties, our initial analysis finds a zonal wind profile
identical to the Voyager and Cassini era profiles at most
latitudes, with some variation in mid- to high-latitude wind
jet magnitudes, particularly at +40° and −35° planetographic
latitude. Further analyses will focus on the complete two-
dimensional wind field.
In addition, the GRS has maintained the intense orange
coloration first observed in 2014, and interpreted as decreased
interaction with nearby wind jets. It also shows new internal
structures and an almost lack of its usual distinct core. The
internal velocity field will need to be examined to determine if
there has been any significant change from previous
measurements.
Finally, a wave feature was also observed near 16° N
latitude, similar to a faint feature observed in Voyager 2
images. It is likely caused by a baroclinic instability that also
forms cyclones, as on Earth and in agreement with Jupiter
analytical models. Further numerical simulation will be needed
to explain why such a feature is not often observed, despite
outwardly similar environmental conditions on other dates.
This work was based on observations made with the NASA/
ESA Hubble Space Telescope under program GO13937.
Support for this program was provided by NASA through a
grant from the Space Telescope Science Institute, which is
operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS5-26555. A.A.S.
thanks Peter Gierasch for informative discussions about wave
formation and baroclinic instabilities.
REFERENCES
Achterberg, R. K., & Ingersoll, A. P. 1989, JAtS, 46, 2448
Asay-Davis, X. S., Marcus, P., Wong, M. H., & de Pater, I. 2011, Icar,
211, 1215
Barrado-Izagirre, N., Rojas, J. F., Hueso, R., et al. 2013, A&A, 554, A74
Beebe, R. F., Orton, G. S., & West, R. A. 1989, Time Variable Phenomenon in
the Jovian System, 245
Blackmon, M. L., Lee, Y.-H., & Wallace, J. M. 1984, JAtS, 41, 961
Charney, J. G. 1947, J. Meteorology, 4, 135
Colina, L., Bohlin, R. C., & Castelli, F. 1996, AJ, 112, 307
Conrath, B. J., Gierasch, P. J., & Nath, N. 1981, Icar, 48, 256
Dressel, L. 2015, Wide Field Camera 3 Instrument Handbook, Version 7.0
(Baltimore: STScI) http://www.stsci.edu/hst/wfc3/documents/handboo
ks/currentIHB/wfc3_cover.html
Eady, E. T. 1949, Tell, 1, 38
Gierasch, P. J., Ingersoll, A. P., & Pollard, D. 1979, Icar, 40, 205
Holton, J. R. 1992, An Introduction to Dynamic Meteorology (3rd ed.; New
York: Academic)
Hunt, G. E., & Muller, J.-P. 1979, Natur, 280, 778
Karkoschka, E. 1998, Icar, 133, 134
Kaspi, Y., & Flierl, G. R. 2007, JAtS, 64, 3177
LeBeau, R. P., & Dowling, T. E. 1998, Icar, 132, 239
Lim, G. H., & Wallace, J. M. 1991, JAtS, 48, 1718
Limaye, S. S. 1989, Time Variable Phenomenon in the Jovian System, 311
Mahaffy, P. R., Niemann, H. B., Alpert, A., et al. 2000, JGRE, 105, 15061
Niemann, H. B., Atreya, S. K., Carignan, G. R., et al. 1998, JGR, 103, 22831
Porco, C. C., West, R. A., McEwen, A., et al. 2003, Sci, 299, 1541
Reuter, D. C., Simon-Miller, A. A., & Lunsford, A. 2007, Sci, 318, 223
Sanchez-Lavega, A., Legarreta, J., Garcia-Melendo, E., et al. 2013, JGRE,
118, 1
Simmons, A. J. 1974, JAtS, 31, 1515
Simon, A. A., Li, L., & Reuter, D. C. 2015a, GeoRL, 42, 2612
Simon, A. A., Sanchez-Lavega, A., Legarreta, J., et al. 2015b, JGRE, 120, 483
Simon, A. A., Wong, M. H., Rogers, J. H., et al. 2014, ApJL, 797, L31
Simon-Miller, A. A., & Gierasch, P. J. 2010, Icar, 210, 258
Simon-Miller, A. A., Gierasch, P. J., Beebe, R. F., et al. 2002, Icar, 158, 249
Simon-Miller, A. A., Rogers, J. H., Gierasch, P. J., et al. 2012, Icar, 218, 817
Smith, B. A., Soderblom, L. A., Banfield, D., et al. 1989, Sci, 246, 1422
Smith, B. A., Soderblom, L. A., Beebe, R. F., et al. 1979, Sci, 206, 927
Stone, P. H. 1969, JAtS, 26, 376
Watkins, C., & Cho, J. Y.-K. 2013, GeoRL, 20, 472
Wong, M. H. 2010, Amplitude of Fringing in WFC3/UVIS Narrowband Red
Filters, Instrument Science Rep. WFC3 2010-04 (Baltimore, MD: Space
Telescope Science Institute)
Wong, M. H. 2011, in Proc. 2010 STScI Calibration Workshop, Fringing in the
WFC3/UVIS Detector, ed. S. Deustua & C. Oliveira (Baltimore, MD:
Space Telescope Science Institute)
Wong, M. H., de Pater, I., Asay-Davis, X. S., Marcus, P. S., & Go, C. Y. 2011,
Icar, 215, 211
Wong, M. H., Mahaffy, P. R., Atreya, S. K., Niemann, H. B., & Owen, T. C.
2004, Icar, 171, 153
Wong, M. H., Simon, A. A., Orton, G. S., de Pater, I., & Sayanagi, K. M. 2015,
in 46th Lunar and Planetary Science Conf., LPI Contribution No. 1777,
2606 http://www.lpi.usra.edu/publications/abstracts.shtml
Yin, J. H., & Battisti, D. S. 2004, JAtS, 61, 1454
8
The Astrophysical Journal, 812:55 (8pp), 2015 October 10 Simon, Wong, & Orton