The document reports the detection of a lunar impact flash by two independent observatories on February 11, 2011. Analysis of video footage from both observatories found that a bright flash occurred simultaneously on the lunar rim at 20:36:58 UTC. The estimated selenographic coordinates of the impact site were 88° ± 2° W and 16° ± 1° S. Modeling of the flash characteristics suggests the impactor had a diameter of 6-8 cm and would have created a crater around 4-5 meters in size.
Stefano Sposetti and Marco Iten detected a probable lunar impact event on February 11, 2011 while monitoring the moon from two separate observatories in Switzerland. Their videos showed a flash of light on the lunar surface at 20:36:58 UTC. Analysis of the light curves and location of the flash place the impact in a region of craters near 86°W, 16°N. The editorial board of Selenology Today notes that images from the Lunar Reconnaissance Orbiter before and after the reported event can be searched to look for an impact crater at the reported coordinates.
This document summarizes research determining the orbit of the potentially hazardous asteroid 2102 Tantalus. Four sets of images of the asteroid were taken using ground-based telescopes. The images were analyzed to determine the asteroid's position over time. Its right ascension and declination were calculated using a least squares plate reduction program. Photometry of the images found apparent magnitudes ranging from 16.0 to 17.5. The orbital elements of the asteroid, including eccentricity, semimajor axis, and inclination, were computed using the method of Gauss. The research provides an improved model of 2102 Tantalus' long-term trajectory.
Every second greater than 1025 antineutrinos radiate to space from Earth, shining like a faint antineutrino
star. Underground antineutrino detectors have revealed the rapidly decaying fission products inside
nuclear reactors, verified the long-lived radioactivity inside our planet, and informed sensitive
experiments for probing fundamental physics. Mapping the anisotropic antineutrino flux and energy
spectrum advance geoscience by defining the amount and distribution of radioactive power within Earth
while critically evaluating competing compositional models of the planet. We present the Antineutrino
Global Map 2015 (AGM2015), an experimentally informed model of Earth’s surface antineutrino flux over
the 0 to 11MeV energy spectrum, along with an assessment of systematic errors. The open source
AGM2015 provides fundamental predictions for experiments, assists in strategic detector placement to
determine neutrino mass hierarchy, and aids in identifying undeclared nuclear reactors. We use
cosmochemically and seismologically informed models of the radiogenic lithosphere/mantle combined
with the estimated antineutrino flux, as measured by KamLAND and Borexino, to determine the Earth’s
total antineutrino luminosity at . × / ν .
.
−
+ 3 4 10 s 2 2
2 3 25
e . We find a dominant flux of geo-neutrinos, predict
sub-equal crust and mantle contributions, with ~1% of the total flux from man-made nuclear reactors.
Geomorphological Mapping Using Remote Sensing and GIS A Tool for Land Use Pla...IOSR Journals
1) The document discusses using remote sensing and GIS techniques to map geomorphological units around Shivpuri City, India using IRS-1D LISS-III satellite imagery from 2006.
2) Six main geomorphic units were identified and mapped - denudational hills, structural hills, residual hills, pediments, pediplains, and alluvial plains.
3) Remote sensing and GIS allowed efficient mapping of the geomorphic units over a large area to inform land use planning decisions by local authorities.
This document summarizes a study that monitored light pollution levels in selected areas of Malaysia using a Sky Quality Meter over 5 months. It found that more populated urban areas like Kuala Lumpur had significantly brighter night skies compared to less populated suburban areas, due to higher levels of artificial light from urban development. The study aimed to determine how light pollution affects the visibility of astronomical objects to the naked eye. It collected hourly measurements in different locations to analyze the relationship between population levels, distance from city centers, and night sky brightness.
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
Spitzer as microlens_parallax_satellite_mass_measurement_for_exoplanet_and_hi...Sérgio Sacani
This document summarizes a study using Spitzer and ground-based observations to measure the microlens parallax vector πE for the first time for a planetary microlensing event, OGLE-2014-BLG-0124L. The πE measurement allows the mass and distance of the planet and its host star to be determined. Spitzer observations provided a 2.5% precision measurement of πE, substantially improving upon the 22% precision from ground data alone. The planet has a mass of about 0.5 Jupiter masses and orbits a star of about 0.7 solar masses at a projected distance of about 3.1 AU.
Stefano Sposetti and Marco Iten detected a probable lunar impact event on February 11, 2011 while monitoring the moon from two separate observatories in Switzerland. Their videos showed a flash of light on the lunar surface at 20:36:58 UTC. Analysis of the light curves and location of the flash place the impact in a region of craters near 86°W, 16°N. The editorial board of Selenology Today notes that images from the Lunar Reconnaissance Orbiter before and after the reported event can be searched to look for an impact crater at the reported coordinates.
This document summarizes research determining the orbit of the potentially hazardous asteroid 2102 Tantalus. Four sets of images of the asteroid were taken using ground-based telescopes. The images were analyzed to determine the asteroid's position over time. Its right ascension and declination were calculated using a least squares plate reduction program. Photometry of the images found apparent magnitudes ranging from 16.0 to 17.5. The orbital elements of the asteroid, including eccentricity, semimajor axis, and inclination, were computed using the method of Gauss. The research provides an improved model of 2102 Tantalus' long-term trajectory.
Every second greater than 1025 antineutrinos radiate to space from Earth, shining like a faint antineutrino
star. Underground antineutrino detectors have revealed the rapidly decaying fission products inside
nuclear reactors, verified the long-lived radioactivity inside our planet, and informed sensitive
experiments for probing fundamental physics. Mapping the anisotropic antineutrino flux and energy
spectrum advance geoscience by defining the amount and distribution of radioactive power within Earth
while critically evaluating competing compositional models of the planet. We present the Antineutrino
Global Map 2015 (AGM2015), an experimentally informed model of Earth’s surface antineutrino flux over
the 0 to 11MeV energy spectrum, along with an assessment of systematic errors. The open source
AGM2015 provides fundamental predictions for experiments, assists in strategic detector placement to
determine neutrino mass hierarchy, and aids in identifying undeclared nuclear reactors. We use
cosmochemically and seismologically informed models of the radiogenic lithosphere/mantle combined
with the estimated antineutrino flux, as measured by KamLAND and Borexino, to determine the Earth’s
total antineutrino luminosity at . × / ν .
.
−
+ 3 4 10 s 2 2
2 3 25
e . We find a dominant flux of geo-neutrinos, predict
sub-equal crust and mantle contributions, with ~1% of the total flux from man-made nuclear reactors.
Geomorphological Mapping Using Remote Sensing and GIS A Tool for Land Use Pla...IOSR Journals
1) The document discusses using remote sensing and GIS techniques to map geomorphological units around Shivpuri City, India using IRS-1D LISS-III satellite imagery from 2006.
2) Six main geomorphic units were identified and mapped - denudational hills, structural hills, residual hills, pediments, pediplains, and alluvial plains.
3) Remote sensing and GIS allowed efficient mapping of the geomorphic units over a large area to inform land use planning decisions by local authorities.
This document summarizes a study that monitored light pollution levels in selected areas of Malaysia using a Sky Quality Meter over 5 months. It found that more populated urban areas like Kuala Lumpur had significantly brighter night skies compared to less populated suburban areas, due to higher levels of artificial light from urban development. The study aimed to determine how light pollution affects the visibility of astronomical objects to the naked eye. It collected hourly measurements in different locations to analyze the relationship between population levels, distance from city centers, and night sky brightness.
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
Spitzer as microlens_parallax_satellite_mass_measurement_for_exoplanet_and_hi...Sérgio Sacani
This document summarizes a study using Spitzer and ground-based observations to measure the microlens parallax vector πE for the first time for a planetary microlensing event, OGLE-2014-BLG-0124L. The πE measurement allows the mass and distance of the planet and its host star to be determined. Spitzer observations provided a 2.5% precision measurement of πE, substantially improving upon the 22% precision from ground data alone. The planet has a mass of about 0.5 Jupiter masses and orbits a star of about 0.7 solar masses at a projected distance of about 3.1 AU.
Lunar skylight polarization signal polluted by urban lightingSérgio Sacani
1. This study found that urban skyglow has a greater degree of linear polarization (8.6%) than expected, which diminishes the natural polarization signal of scattered moonlight.
2. Measurements taken in Berlin found the lunar polarization signal was clearly visible in a rural area 28 km from the city center (29.2%), but was reduced within the city itself (11.3%).
3. Without the influence of skyglow, the lunar polarization signal would likely exceed 50%. This indicates that nocturnal animal navigation systems relying on perceiving polarized moonlight likely fail in highly light-polluted urban areas.
Discrete and broadband electron acceleration in Jupiter’s powerful auroraSérgio Sacani
The most intense auroral emissions from Earth’s polar regions,
called discrete for their sharply defined spatial configurations, are
generated by a process involving coherent acceleration of electrons
by slowly evolving, powerful electric fields directed along the
magnetic field lines that connect Earth’s space environment to its
polar regions1,2. In contrast, Earth’s less intense auroras are generally
caused by wave scattering of magnetically trapped populations of
hot electrons (in the case of diffuse aurora) or by the turbulent or
stochastic downward acceleration of electrons along magnetic field
lines by waves during transitory periods (in the case of broadband
or Alfvénic aurora)3,4. Jupiter’s relatively steady main aurora has a
power density that is so much larger than Earth’s that it has been
taken for granted that it must be generated primarily by the discrete
auroral process5–7. However, preliminary in situ measurements of
Jupiter’s auroral regions yielded no evidence of such a process8–10.
Here we report observations of distinct, high-energy, downward,
discrete electron acceleration in Jupiter’s auroral polar regions. We
also infer upward magnetic-field-aligned electric potentials of up to
400 kiloelectronvolts, an order of magnitude larger than the largest
potentials observed at Earth11. Despite the magnitude of these
upward electric potentials and the expectations from observations
at Earth, the downward energy flux from discrete acceleration is less
at Jupiter than that caused by broadband or stochastic processes,
with broadband and stochastic characteristics that are substantially
different from those at Earth.
1) Magnitude measures the actual size of an earthquake based on the amount of energy released, while intensity measures the strength of shaking felt at a given location.
2) Magnitude is a single value for each earthquake, but the same earthquake can produce different intensities of shaking at different locations depending on their distance from the epicenter.
3) Buildings are designed to withstand certain intensity levels of shaking rather than specific magnitudes, since the same magnitude earthquake can produce varying intensities of shaking in different areas.
Multi-phase volcanic resurfacing at Loki Patera on IoSérgio Sacani
The Jovian moon Io hosts the most powerful persistently active
volcano in the Solar System, Loki Patera1,2. The interior of this
volcanic, caldera-like feature is composed of a warm, dark floor
covering 21,500 square kilometres3 surrounding a much cooler
central ‘island’4. The temperature gradient seen across areas of
the patera indicates a systematic resurfacing process4–9, which
has been seen to occur typically every one to three years since the
1980s5,10. Analysis of past data has indicated that the resurfacing
progressed around the patera in an anti-clockwise direction at a
rate of one to two kilometres per day, and that it is caused either
by episodic eruptions that emplace voluminous lava flows or by a
cyclically overturning lava lake contained within the patera5,8,9,11.
However, spacecraft and telescope observations have been unable to
map the emission from the entire patera floor at sufficient spatial
resolution to establish the physical processes at play. Here we report
temperature and lava cooling age maps of the entire patera floor at
a spatial sampling of about two kilometres, derived from groundbased
interferometric imaging of thermal emission from Loki Patera
obtained on 8 March 2015 ut as the limb of Europa occulted Io.
Our results indicate that Loki Patera is resurfaced by a multi-phase
process in which two waves propagate and converge around the
central island. The different velocities and start times of the waves
indicate a non-uniformity in the lava gas content and/or crust bulk
density across the patera.
ALOS urgent observation - Results from the Tohoku-Oki M9.0 Earthquake and the...grssieee
1) ALOS observed flooded areas and damage from the Tohoku earthquake and tsunami using AVNIR-2, PALSAR amplitude images, and interferometry.
2) PALSAR full polarimetry was used to compare parameters before and after the disaster over areas with collapsed buildings due to tsunami.
3) Collapsed buildings showed surface scattering with high entropy and non-reflection symmetry after the disaster.
A surge of light at the birth of a supernovaSérgio Sacani
It is difficult to establish the properties of massive stars that explode
as supernovae1,2
. The electromagnetic emission during the first
minutes to hours after the emergence of the shock from the stellar
surface conveys important information about the final evolution
and structure of the exploding star3–6. However, the unpredictable
nature of supernova events hinders the detection of this brief initial
phase7–9. Here we report the serendipitous discovery of a newly
born, normal type IIb supernova (SN 2016gkg)10, which reveals a
rapid brightening at optical wavelengths of about 40 magnitudes
per day. The very frequent sampling of the observations allowed
us to study in detail the outermost structure of the progenitor of
the supernova and the physics of the emergence of the shock. We
develop hydrodynamical models of the explosion that naturally
account for the complete evolution of the supernova over distinct
phases regulated by different physical processes. This result
suggests that it is appropriate to decouple the treatment of the
shock propagation from the unknown mechanism that triggers
the explosion.
This document discusses variations in multiple atmospheric parameters (outgoing longwave radiation, surface latent heat flux, air temperature, relative humidity, and air pressure) prior to the 2008 Mw 8.0 Wenchuan earthquake in China. The results show significant anomalies in these parameters starting 2 weeks before the quake. Outgoing longwave radiation anomalies were first observed 13 days beforehand and covered an area of 20,000 km2 along the fault zone. Surface latent heat flux showed anomalies the day before the earthquake. The variations are attributed to energy accumulation and release related to the tectonic stress buildup along the fault that caused the earthquake.
This document analyzes spectral ratios computed from accelerations recorded during the 2017 M 7.1 Puebla-Morelos earthquake in Mexico City. The spectral ratios reveal predominant periods that are consistent with Mexico City's 2004 seismic zoning code. Both horizontal-to-horizontal and horizontal-to-vertical spectral ratio methods identify similar frequencies that validate studies using recordings from the 1985 M 8.1 Michoacán earthquake. The consistent predominant periods observed confirm the specific frequency characterizations of Mexico City's different seismic zones outlined in the 2004 code.
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
This research project aimed to determine the relationship between earthquakes detected by seismometers at the LIGO-Hanford Observatory and the sensitivity of the LIGO interferometers to gravitational waves. The student collected data on earthquakes and interferometer sensitivity in 2007. By comparing earthquake data to seismometer readings and sensitivity measurements, some earthquakes were confirmed to affect interferometer sensitivity. However, the relationships between sensitivity and individual earthquake attributes like distance, magnitude, and depth were inconclusive. Further data and analysis are needed to fully model how earthquakes impact LIGO interferometer measurements.
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.
What Do Ground Motion Prediction Equations Tell Us?Ali Osman Öncel
Ground motion prediction equations (GMPEs) provide simple equations to estimate ground motion levels based on magnitude, distance, site conditions, and other variables. While useful for engineering applications, GMPEs tell us little about ground motion variability near faults as they provide average motions from many recordings. Near-fault recordings of large earthquakes can provide more insight, showing variations in amplitude and polarization due to nonuniform fault slip, site effects, and fault zone effects. The dense network of stations recording the 2004 M6.0 Parkfield earthquake revealed less spatial variability for longer period ground motions compared to higher frequencies.
This document provides an overview of deterministic seismic ground motions and the PEER NGA ground motion prediction equations (GMPEs). It discusses what GMPEs are and how they are used. The document outlines the development of GMPEs, including the data and functions used as well as comparisons of median predictions and uncertainties. It also reviews the PEER NGA-West2 GMPEs and compares predictions to Greek data. Key variables in GMPEs like magnitude, distance, site effects and response spectra are defined.
VIMS images of the Huygens landing site on Titan acquired during Cassini flybys in October and December 2004 provide insight into surface features near the landing site with spatial resolutions of 14.4-19 km/pixel. Ratio images of the brightest and darkest spectra in the 2.03 μm window reveal a particularly contrasted structure north of the landing site, consistent with local enrichment in exposed water ice. The images also show a possible 150 km diameter impact crater with a central peak. While scattering from haze particles dominates Titan's spectrum, spectral ratios of bright and dark areas suggest differences in surface composition and/or topography related to DISR images of the site.
Incorporated Research Institue for Seismology does an amazing job at providing detailed information shortly after large earthquakes. Learn more at: http://www.iris.edu/hq/retm
Rupture processes of the 2012 September 5 Mw 7.6 Nicoya CONSTRAINEDAllan Lopez
On September 5, 2012, a Mw 7.6 earthquake ruptured beneath the Nicoya Peninsula in northwestern Costa Rica. Extensive geodetic and seismological observations from dense near-field strong motion sensors, GPS networks, and global seismic networks provide a unique opportunity to investigate the rupture process. Through a non-linear joint inversion of high-rate GPS waveforms, static GPS offsets, strong motion data, and teleseismic body waves, the authors obtained a robust rupture model. The earthquake was dominantly a pure thrust event with a maximum slip of 3.5 m located below the hypocenter, spanning about 50 km along dip and 110 km along strike. The static stress drop was approximately 3.4 MP
This document summarizes research determining the velocity vector of the Andromeda Galaxy (M31) relative to the Milky Way using Hubble Space Telescope measurements of M31's proper motion. N-body models of M31 are used to correct for internal stellar motions within M31. The results imply M31 is on a radial orbit towards the Milky Way. The velocity vector is then used to estimate the mass of the Local Group, obtaining a value of (3.17 ± 0.57) × 1012 M☉. It is also implied M33 is likely bound to M31.
Hulusi Behçet (Istanbul, 20 February 1889 - 8 March 1948) was a Turkish dermatologist and scientist. He described a disease of inflamed blood vessels in 1937, which is named after him as the Behçet's disease.
Erica Block completed an 11-week internship with wedding planner Jaime Nelson of Eventfully Planned. During her internship, Erica assisted with 7 weddings by setting up receptions, working with vendors, and creating wedding timelines. She gained experience in tasks like coordinating large events, managing budgets, and assessing intoxication levels. Erica's coursework in areas like crowd control, organization, time management, and alcohol management proved useful. The internship helped Erica achieve her goals of learning about wedding planning, different types of brides, and vendor contracts.
Lunar skylight polarization signal polluted by urban lightingSérgio Sacani
1. This study found that urban skyglow has a greater degree of linear polarization (8.6%) than expected, which diminishes the natural polarization signal of scattered moonlight.
2. Measurements taken in Berlin found the lunar polarization signal was clearly visible in a rural area 28 km from the city center (29.2%), but was reduced within the city itself (11.3%).
3. Without the influence of skyglow, the lunar polarization signal would likely exceed 50%. This indicates that nocturnal animal navigation systems relying on perceiving polarized moonlight likely fail in highly light-polluted urban areas.
Discrete and broadband electron acceleration in Jupiter’s powerful auroraSérgio Sacani
The most intense auroral emissions from Earth’s polar regions,
called discrete for their sharply defined spatial configurations, are
generated by a process involving coherent acceleration of electrons
by slowly evolving, powerful electric fields directed along the
magnetic field lines that connect Earth’s space environment to its
polar regions1,2. In contrast, Earth’s less intense auroras are generally
caused by wave scattering of magnetically trapped populations of
hot electrons (in the case of diffuse aurora) or by the turbulent or
stochastic downward acceleration of electrons along magnetic field
lines by waves during transitory periods (in the case of broadband
or Alfvénic aurora)3,4. Jupiter’s relatively steady main aurora has a
power density that is so much larger than Earth’s that it has been
taken for granted that it must be generated primarily by the discrete
auroral process5–7. However, preliminary in situ measurements of
Jupiter’s auroral regions yielded no evidence of such a process8–10.
Here we report observations of distinct, high-energy, downward,
discrete electron acceleration in Jupiter’s auroral polar regions. We
also infer upward magnetic-field-aligned electric potentials of up to
400 kiloelectronvolts, an order of magnitude larger than the largest
potentials observed at Earth11. Despite the magnitude of these
upward electric potentials and the expectations from observations
at Earth, the downward energy flux from discrete acceleration is less
at Jupiter than that caused by broadband or stochastic processes,
with broadband and stochastic characteristics that are substantially
different from those at Earth.
1) Magnitude measures the actual size of an earthquake based on the amount of energy released, while intensity measures the strength of shaking felt at a given location.
2) Magnitude is a single value for each earthquake, but the same earthquake can produce different intensities of shaking at different locations depending on their distance from the epicenter.
3) Buildings are designed to withstand certain intensity levels of shaking rather than specific magnitudes, since the same magnitude earthquake can produce varying intensities of shaking in different areas.
Multi-phase volcanic resurfacing at Loki Patera on IoSérgio Sacani
The Jovian moon Io hosts the most powerful persistently active
volcano in the Solar System, Loki Patera1,2. The interior of this
volcanic, caldera-like feature is composed of a warm, dark floor
covering 21,500 square kilometres3 surrounding a much cooler
central ‘island’4. The temperature gradient seen across areas of
the patera indicates a systematic resurfacing process4–9, which
has been seen to occur typically every one to three years since the
1980s5,10. Analysis of past data has indicated that the resurfacing
progressed around the patera in an anti-clockwise direction at a
rate of one to two kilometres per day, and that it is caused either
by episodic eruptions that emplace voluminous lava flows or by a
cyclically overturning lava lake contained within the patera5,8,9,11.
However, spacecraft and telescope observations have been unable to
map the emission from the entire patera floor at sufficient spatial
resolution to establish the physical processes at play. Here we report
temperature and lava cooling age maps of the entire patera floor at
a spatial sampling of about two kilometres, derived from groundbased
interferometric imaging of thermal emission from Loki Patera
obtained on 8 March 2015 ut as the limb of Europa occulted Io.
Our results indicate that Loki Patera is resurfaced by a multi-phase
process in which two waves propagate and converge around the
central island. The different velocities and start times of the waves
indicate a non-uniformity in the lava gas content and/or crust bulk
density across the patera.
ALOS urgent observation - Results from the Tohoku-Oki M9.0 Earthquake and the...grssieee
1) ALOS observed flooded areas and damage from the Tohoku earthquake and tsunami using AVNIR-2, PALSAR amplitude images, and interferometry.
2) PALSAR full polarimetry was used to compare parameters before and after the disaster over areas with collapsed buildings due to tsunami.
3) Collapsed buildings showed surface scattering with high entropy and non-reflection symmetry after the disaster.
A surge of light at the birth of a supernovaSérgio Sacani
It is difficult to establish the properties of massive stars that explode
as supernovae1,2
. The electromagnetic emission during the first
minutes to hours after the emergence of the shock from the stellar
surface conveys important information about the final evolution
and structure of the exploding star3–6. However, the unpredictable
nature of supernova events hinders the detection of this brief initial
phase7–9. Here we report the serendipitous discovery of a newly
born, normal type IIb supernova (SN 2016gkg)10, which reveals a
rapid brightening at optical wavelengths of about 40 magnitudes
per day. The very frequent sampling of the observations allowed
us to study in detail the outermost structure of the progenitor of
the supernova and the physics of the emergence of the shock. We
develop hydrodynamical models of the explosion that naturally
account for the complete evolution of the supernova over distinct
phases regulated by different physical processes. This result
suggests that it is appropriate to decouple the treatment of the
shock propagation from the unknown mechanism that triggers
the explosion.
This document discusses variations in multiple atmospheric parameters (outgoing longwave radiation, surface latent heat flux, air temperature, relative humidity, and air pressure) prior to the 2008 Mw 8.0 Wenchuan earthquake in China. The results show significant anomalies in these parameters starting 2 weeks before the quake. Outgoing longwave radiation anomalies were first observed 13 days beforehand and covered an area of 20,000 km2 along the fault zone. Surface latent heat flux showed anomalies the day before the earthquake. The variations are attributed to energy accumulation and release related to the tectonic stress buildup along the fault that caused the earthquake.
This document analyzes spectral ratios computed from accelerations recorded during the 2017 M 7.1 Puebla-Morelos earthquake in Mexico City. The spectral ratios reveal predominant periods that are consistent with Mexico City's 2004 seismic zoning code. Both horizontal-to-horizontal and horizontal-to-vertical spectral ratio methods identify similar frequencies that validate studies using recordings from the 1985 M 8.1 Michoacán earthquake. The consistent predominant periods observed confirm the specific frequency characterizations of Mexico City's different seismic zones outlined in the 2004 code.
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
This research project aimed to determine the relationship between earthquakes detected by seismometers at the LIGO-Hanford Observatory and the sensitivity of the LIGO interferometers to gravitational waves. The student collected data on earthquakes and interferometer sensitivity in 2007. By comparing earthquake data to seismometer readings and sensitivity measurements, some earthquakes were confirmed to affect interferometer sensitivity. However, the relationships between sensitivity and individual earthquake attributes like distance, magnitude, and depth were inconclusive. Further data and analysis are needed to fully model how earthquakes impact LIGO interferometer measurements.
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.
What Do Ground Motion Prediction Equations Tell Us?Ali Osman Öncel
Ground motion prediction equations (GMPEs) provide simple equations to estimate ground motion levels based on magnitude, distance, site conditions, and other variables. While useful for engineering applications, GMPEs tell us little about ground motion variability near faults as they provide average motions from many recordings. Near-fault recordings of large earthquakes can provide more insight, showing variations in amplitude and polarization due to nonuniform fault slip, site effects, and fault zone effects. The dense network of stations recording the 2004 M6.0 Parkfield earthquake revealed less spatial variability for longer period ground motions compared to higher frequencies.
This document provides an overview of deterministic seismic ground motions and the PEER NGA ground motion prediction equations (GMPEs). It discusses what GMPEs are and how they are used. The document outlines the development of GMPEs, including the data and functions used as well as comparisons of median predictions and uncertainties. It also reviews the PEER NGA-West2 GMPEs and compares predictions to Greek data. Key variables in GMPEs like magnitude, distance, site effects and response spectra are defined.
VIMS images of the Huygens landing site on Titan acquired during Cassini flybys in October and December 2004 provide insight into surface features near the landing site with spatial resolutions of 14.4-19 km/pixel. Ratio images of the brightest and darkest spectra in the 2.03 μm window reveal a particularly contrasted structure north of the landing site, consistent with local enrichment in exposed water ice. The images also show a possible 150 km diameter impact crater with a central peak. While scattering from haze particles dominates Titan's spectrum, spectral ratios of bright and dark areas suggest differences in surface composition and/or topography related to DISR images of the site.
Incorporated Research Institue for Seismology does an amazing job at providing detailed information shortly after large earthquakes. Learn more at: http://www.iris.edu/hq/retm
Rupture processes of the 2012 September 5 Mw 7.6 Nicoya CONSTRAINEDAllan Lopez
On September 5, 2012, a Mw 7.6 earthquake ruptured beneath the Nicoya Peninsula in northwestern Costa Rica. Extensive geodetic and seismological observations from dense near-field strong motion sensors, GPS networks, and global seismic networks provide a unique opportunity to investigate the rupture process. Through a non-linear joint inversion of high-rate GPS waveforms, static GPS offsets, strong motion data, and teleseismic body waves, the authors obtained a robust rupture model. The earthquake was dominantly a pure thrust event with a maximum slip of 3.5 m located below the hypocenter, spanning about 50 km along dip and 110 km along strike. The static stress drop was approximately 3.4 MP
This document summarizes research determining the velocity vector of the Andromeda Galaxy (M31) relative to the Milky Way using Hubble Space Telescope measurements of M31's proper motion. N-body models of M31 are used to correct for internal stellar motions within M31. The results imply M31 is on a radial orbit towards the Milky Way. The velocity vector is then used to estimate the mass of the Local Group, obtaining a value of (3.17 ± 0.57) × 1012 M☉. It is also implied M33 is likely bound to M31.
Hulusi Behçet (Istanbul, 20 February 1889 - 8 March 1948) was a Turkish dermatologist and scientist. He described a disease of inflamed blood vessels in 1937, which is named after him as the Behçet's disease.
Erica Block completed an 11-week internship with wedding planner Jaime Nelson of Eventfully Planned. During her internship, Erica assisted with 7 weddings by setting up receptions, working with vendors, and creating wedding timelines. She gained experience in tasks like coordinating large events, managing budgets, and assessing intoxication levels. Erica's coursework in areas like crowd control, organization, time management, and alcohol management proved useful. The internship helped Erica achieve her goals of learning about wedding planning, different types of brides, and vendor contracts.
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Transit timing observations from kepler i. statistical analysis of the first...Sérgio Sacani
This document analyzes transit timing observations from the first four months of Kepler mission data. It finds that at least 12% (~65) of planet candidates show evidence of transit timing variations (TTVs), suggesting non-Keplerian motion likely due to gravitational interactions with other planets. While longer observation time is needed, TTVs could confirm multiple planet systems identified by Kepler and provide insights into planetary system dynamics and planet formation. The analysis measures individual transit times, assesses the significance of any variations compared to linear and quadratic ephemeris models, and identifies planet candidates warranting further TTV study.
Persistence of black holes through a cosmological bounceSérgio Sacani
The document discusses whether black holes could persist through a cosmological bounce, where the universe recollapses and then bounces into a new expansion phase. It finds that there is a mass range where black holes could form during the big crunch ("BCBHs") without merging with pre-existing black holes ("PCBHs"). This mass range depends on factors like the density at bounce and whether extra dimensions exist. Observational signatures could distinguish black holes forming just before or after the bounce. The persistence of black holes relates to issues in cyclic cosmology models and scenarios where the universe evolves to maximize black hole formation.
Black hole growth in the early universe is self regulated and largely hidde...Sérgio Sacani
The study analyzed X-ray data from the Chandra X-ray Observatory to measure black hole growth in galaxies between redshifts 6-8 (0.95-0.7 billion years after the Big Bang). It found:
1) A stacked signal from 197 galaxies at z<6 detected significant X-ray emission, implying black holes grew in tandem with their host galaxies throughout cosmic history.
2) Most vigorously accreting black holes at these early epochs were obscured by significant gas and dust, absorbing most radiation except high-energy X-rays.
3) The obscured black hole growth suggests growth was significantly more than previously thought, but the obscuration prevented contribution to reionizing the Universe.
High pre eruptive water contents preserved in lunar melt inclusionsSérgio Sacani
This study analyzed melt inclusions trapped in olivine crystals from lunar volcanic glass samples. The melt inclusions contained 615-1410 parts per million of water, much higher than previous measurements of lunar samples. They also contained high amounts of fluorine, sulfur, and chlorine similar to primitive terrestrial basalts. This indicates that parts of the lunar interior contain as much water as Earth's upper mantle, challenging theories that the Moon lost its entire volatile inventory during formation. The similarities between the lunar melt inclusions and terrestrial basalts suggest the lunar mantle source was similar in volatile content to Earth's upper mantle.
A super earth transiting a naked-eye starSérgio Sacani
This document summarizes the detection of transits of an exoplanet orbiting the star 55 Cnc, using photometry from the MOST space telescope. The transits match the period, phase, duration, and depth predicted for the innermost planet of 55 Cnc, designated 55 Cnc e. Analysis of the transit data indicates the planet has a mass of 8.57 Earth masses, a radius of 1.63 Earth radii, and a dense composition of rock and iron. This makes 55 Cnc e similar to other dense super-Earth exoplanets in short orbits, unlike lower-density super-Earths further from their stars. The brightness of 55 Cnc will enable further study of this transiting exoplanet system.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
John MacArthur, “Agape love is the greatest virtue of the Christian life. Yet that type of love was rare in pagan Greek literature. That’s because the traits agape portrays—unselfishness, self-giving, willful devotion, concern for the welfare of others—were mostly disdained in ancient Greek culture as signs of weakness. However, the ew Testament declares agape to be the character trait around which
all others revolve. The apostle John writes, “God is love, and the one who abides in love abides in God, and God abides in him” (1 John 4:16).
Backreaction of hawking_radiation_on_a_gravitationally_collapsing_star_2_fire...Sérgio Sacani
This document summarizes a numerical study of the backreaction of Hawking radiation on a gravitationally collapsing star. The study finds that including the inward flux of negative energy Hawking radiation in the interior of the star slows its collapse. This causes the star to bounce at a finite radius larger than its horizon, before its core explodes. The full system of Einstein and hydrodynamic equations describing the collapsing star and Hawking radiation flux are solved numerically, as an improvement over previous analytic approximations.
Solar limb darkening_function_from_baily_beads_observationsSérgio Sacani
This document presents a new method for measuring the solar limb darkening function using observations of Baily's beads during solar eclipses. The method involves analyzing the light curve profiles of emerging and disappearing Baily's beads to determine the surface brightness profile of the outer solar atmosphere with high resolution. The method is applied to eclipse videos from 2010, yielding constraints on the position of the limb darkening function inflection point between -0.190 and +0.050 arcseconds. The results suggest reconsidering evaluations of historical eclipses that assumed a step function profile for the limb darkening.
This document summarizes a study of a Coronal Mass Ejection (CME) event observed on July 26, 2013 using multiple instruments. Observations from SDO, STEREO, PROBA2 and GOES were analyzed using image processing techniques to track the height-time evolution of the erupting prominence. The study aims to better understand the early evolution of CMEs through characterizing the initiation and acceleration profiles of the associated prominence. Multiscale image processing like Multiscale Gaussian Normalization and wavelet analysis were applied to enhance fine structures in the data. Kinematic profiles were derived from stack plots of different wavelengths using techniques like the Savitzky-Golay filter. Preliminary results found an initially stable prominence
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Matter ejections behind the highs and lows of the transitional millisecond pu...Sérgio Sacani
Transitional millisecond pulsars are an emerging class of sources linking low-mass X-ray binaries to millisecond radio pulsars in
binary systems. These pulsars alternate between a radio pulsar state and an active low-luminosity X-ray disc state. During the active
state, these sources exhibit two distinct emission modes (high and low) that alternate unpredictably, abruptly, and incessantly. X-ray
to optical pulsations are observed only during the high mode. Knowledge of the root reason for this puzzling behaviour remains
elusive. This paper presents the results of the most extensive multi-wavelength campaign ever conducted on the transitional pulsar
prototype, PSR J1023+0038, covering from radio to X-rays. The campaign was carried out over two nights in June 2021, and involved
12 different telescopes and instruments including XMM-Newton, HST, VLT/FORS2 (in polarimetric mode), ALMA, VLA and FAST.
By modelling the broadband spectral energy distributions in both emission modes, we show that the mode switches are caused by
changes in the innermost region of the accretion disc. These changes trigger the emission of discrete mass ejections, which occur on
top of a compact jet, as testified by the detection of at least one short-duration millimetre flare with A
The pillars of_creation_revisited_with_muse_gas_kinematics_and_high_mass_stel...Sérgio Sacani
The document discusses observations of the Pillars of Creation in the Eagle Nebula using integral field spectroscopy from the MUSE instrument on the VLT. For the first time, the study maps physical parameters like extinction, density, temperature, and velocity across the pillars. The data show that the pillar tips have high densities and are being photoevaporated by the massive stars in NGC 6611. The kinematics indicate a blueshifted photoevaporative flow, consistent with simulations. The 3D geometry of the pillars is inferred, with some in front of and some behind the ionizing stars. A previously unknown outflow is detected from the middle pillar, suggesting an embedded protostar.
1) Astronomers observed comet Hale-Bopp at 30.7 AU from the Sun using the ESO 2.2m telescope in Chile on December 4, 2010.
2) They detected the comet with a total brightness of R=23.3 mag, corresponding to an absolute brightness of R(1,1,0)=8.3 mag.
3) The profile of the comet was star-like without any evidence of an extended coma or tail, indicating a cessation of matter production from the comet. However, the measured brightness corresponds to a reflecting surface area nine times smaller than three years prior, suggesting some low-level activity may still be occurring.
We describe the discovery of a satellite in orbit about the dwarf planet (136472) Makemake. This
satellite, provisionally designated S/2015 (136472) 1, was detected in imaging data collected with the
Hubble Space Telescope’s Wide Field Camera 3 on UTC April 27, 2015 at 7.80±0.04 magnitudes
fainter than Makemake. It likely evaded detection in previous satellite searches due to a nearly edgeon
orbital configuration, placing it deep within the glare of Makemake during a substantial fraction
of its orbital period. This configuration would place Makemake and its satellite near a mutual event
season. Insufficient orbital motion was detected to make a detailed characterization of its orbital
properties, prohibiting a measurement of the system mass with the discovery data alone. Preliminary
analysis indicates that if the orbit is circular, its orbital period must be longer than 12.4 days, and
must have a semi-major axis &21,000 km. We find that the properties of Makemake’s moon suggest
that the majority of the dark material detected in the system by thermal observations may not reside
on the surface of Makemake, but may instead be attributable to S/2015 (136472) 1 having a uniform
dark surface. This “dark moon hypothesis” can be directly tested with future JWST observations.
We discuss the implications of this discovery for the spin state, figure, and thermal properties of
Makemake and the apparent ubiquity of trans-Neptunian dwarf planet satellites.
Imaging the dust_sublimation_front_of_a_circumbinary_diskSérgio Sacani
Aims. We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust.
Methods. A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera
on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed
by combining the data of all spectral channels using the SPARCO method.
Results. We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our
dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an
unexpected flux signal of 4% from the secondary star. The energy output from this companion indicates the presence of a compact
circum-companion accretion disk, which is likely the origin of the fast outflow detected in H.
Conclusions. Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate
that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time.
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
The Internal Structure of Asteroid (25143) Itokawa as Revealed by Detection o...WellingtonRodrigues2014
- The authors detected an acceleration in the rotation rate of asteroid (25143) Itokawa through photometric observations spanning 2001 to 2013.
- By measuring rotational phase offsets between observed and modeled lightcurves, they found a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year.
- Thermophysical modeling of the detailed shape model from the Hayabusa spacecraft could not reconcile the observed YORP strength unless the asteroid's center of mass is shifted by about 21 m along its long axis. This suggests Itokawa has two components with different densities that merged, either from a
The internal structure_of_asteroid_itokawa_as_revealed_by_detection_of_yorp_s...Sérgio Sacani
The study detected an acceleration in the rotation rate of asteroid (25143) Itokawa through long-term photometric monitoring between 2001-2013. By measuring rotational phase offsets between observed and modeled lightcurves, a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2 was measured, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year. Thermophysical analysis of the detailed shape model from the Hayabusa spacecraft found that the center-of-mass must be offset by about 21 m along the long axis to reconcile the observed and theoretical YORP strengths, suggesting Itokawa is composed of two separate bodies with densities of 1750 ± 110 kg m
Discovery of powerful gamma ray flares from the crab nebulaSérgio Sacani
1) The AGILE satellite detected powerful gamma-ray flares from the Crab Nebula in September 2010 and October 2007 that increased the nebula's unpulsed gamma-ray flux by a factor of 3.
2) The flares originated near the nebula's central pulsar and challenge standard models of nebular emission.
3) Synchrotron emission from shock-accelerated electrons along the pulsar's polar jet can explain the gamma-ray flaring, requiring particle acceleration on timescales of about 1 day.
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where σ is the Stefan-Boltzmann constant.
1) The document discusses a computer simulation called Starsmasher that astrophysicists use to model binary star mergers like that of V1309 Scorpii.
2) Starsmasher uses smoothed particle hydrodynamics (SPH) which treats fluids as interacting parcels to efficiently simulate gas dynamics in stellar events.
3) The document provides details on how Starsmasher simulations work and the goals of modeling the light curve and visual appearance of V1309 Scorpii's merger event.
The document discusses Earth's magnetic field, which is generated in the liquid outer core by electrical currents. It can be observed to vary in space and time due to processes within Earth and from the Sun. Observations are made at geomagnetic observatories, through surveys on land and from aircraft/satellites, and by studying rocks' magnetic properties. The field can both aid navigation/drilling and interfere with satellite operations.
The hazardous km-sized NEOs of the next thousands of yearsSérgio Sacani
This document discusses methods for assessing the long-term impact risk of km-sized near-Earth objects (NEOs) over thousands of years. It analyzes the evolution of the Minimum Orbit Intersection Distance (MOID) between NEOs and Earth to identify objects that remain in close proximity for extended periods. It then estimates the probability of a deep Earth encounter during these low-MOID periods based on the growth of orbital uncertainties over time. This allows the authors to rank km-sized NEOs by their long-term impact hazard and identify targets that warrant further observation and analysis.
Observation of large scale precursor correlations between cosmic rays and ear...Sérgio Sacani
The search for correlations between secondary cosmic ray detection rates and seismic
effects has long been a subject of investigation motivated by the hope of identifying a new
precursor type that could feed a global early warning system against earthquakes. Here we show
for the first time that the average variation of the cosmic ray detection rates correlates with the
global seismic activity to be observed with a time lag of approximately two weeks, and that the
significance of the effect varies with a periodicity resembling the undecenal solar cycle, with a
shift in phase of around three years, exceeding 6 𝜎 at local maxima. The precursor characteristics
of the observed correlations point to a pioneer perspective of an early warning system against
earthquakes.
1) High-dispersion spectroscopy was used to observe the young exoplanet Beta Pictoris b, detecting a blueshifted radial velocity of -15±1.7 km/s and rotational broadening of 25±3 km/s, indicating it spins faster than any planet in the solar system.
2) Beta Pictoris b's high spin velocity is consistent with an extrapolation of the trend of increasing spin velocity with planet mass seen in the solar system.
3) At an estimated age of 11±5 Myr, Beta Pictoris b is expected to cool and shrink over time, which would cause it to spin up further to a rotation velocity of around 40 km/s.
This project uses computer simulations to model observations of the 2005 Deep Impact collision with comet Tempel 1. The simulations aim to understand the physics behind the light curves observed by Hubble Space Telescope. The simulations suggest the optically thick ejecta cloud was about 28 km in diameter 13 minutes after impact and expanding at around 36 m/s, constraining the cloud's mass to approximately 2x10^7 kg. This mass and expansion velocity are consistent with independent estimates from observations by different astronomy groups.
A multi wavelength_analysis_of_m8_insight_on_the_nature_of_arp_loopSérgio Sacani
This document presents a multi-wavelength analysis of M81 and Arp's loop, a peculiar ring-like structure around M81. Optical images reveal Arp's loop has a filamentary structure with many overlapping dust features. Infrared images show Arp's loop has infrared colors and emission properties similar to Galactic cirrus clouds in the region. The results suggest the light at optical wavelengths comes from recent star formation near M81, M81's extended disk, and scattered light from Galactic cirrus, while the infrared emission is dominated by cold dust from Galactic cirrus.
Studies of ngc_6720_with_calibrated_hst_wfc3_emission_line_filter_imagesSérgio Sacani
This study uses calibrated Hubble Space Telescope images of the Ring Nebula (NGC 6720) taken 12.925 years apart to measure tangential motions within the nebula. Individual features were measured in nitrogen emission line images as well as dark knots seen against oxygen emission. The results indicate that the nebula is expanding homologously, but at a faster rate along its major axis. Dark knots were found to expand more slowly than the nebular gas. The tangential motion measurements allow estimates of the nebula's distance and dynamic age to be about 720 pc and 4000 years, respectively.
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.
2. Selenology Today is devoted to the publi-
cation of contributions in the field of lunar
Pagina 2
studies. Manuscripts reporting the results of
new research concerning the astronomy, ge-
ology, physics, chemistry and other scien-
Editor-in-Chief: tific aspects of Earth’s Moon are welcome.
Selenology Today publishes papers de-
R. Lena voted exclusively to the Moon.
Reviews, historical papers and manu-
Editors:
scripts describing observing or spacecraft
M.T. Bregante instrumentation are considered.
J. Phillips The Selenology Today
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Selenology Today # 23 Special edition March 2011
3. SELENOLOGY TODAY #23
March 2011
Selenology Today website
http://digilander.libero.it/glrgroup/
DETECTION OF A METEOROIDAL IMPACT ON THE MOON
By S. Sposetti , M. Iten and R. Lena ………………………………………...1
………………………………………...1
Selenology Today # 23 Special edition March 2011
Selenology Today # 23 Special edition March 2011
4. LUNAR IMPACT SELENOLOGY TODAY 23
Detection of a meteoroidal impact on the Moon
By Stefano Sposetti (a), Marco Iten (b)
and Raffaello Lena (c)
(a) Gnosca Observatory (Switzerland)
(b) Garden Observatory (Switzerland)
(c) Geologic Lunar Research (GLR) group
Abstract
In this article we report data about a lunar flash detected on February 11, 2011 which
very likely resulted from an impact. It was simultaneously detected by two independent
observatories. The brightest impact flash reached a peak brightness of 8.1 ± 0.3 magV
and had a long lasting afterglow. The selenographic coordinates of the lunar impact
flash are determined to 88° ± 2° W and 16° ± 1° S. In addition we examine the flash
characteristics in order to exclude further lunar flash sources, e.g cosmic rays, noise,
meteors and artificial satellite glints. The examined impact flash probably corresponds
to a sporadic event because no major meteor showers were active or exhibit favourable
impact geometry on the impact date. Based on a modelling analysis, the mass of the
impactor is estimated assuming a conversion efficiency from kinetic to optical energy of
2×10 -3 and 2×10 -2. The results show that the meteoroid is likely to range in size from
about 6 to 8 cm in diameter and produced a crater of about 4-5 m in diameter.
1. Introduction
On November 18, 1999, the first confirmed lunar meteoritic impacts were recorded in the
form of flashes that resulted from the collision of the Moon with debris within the Leonid
meteoroid stream (Cudnik et al., 2003). The development and widespread use of
videorecording equipment has recently made it possible to conduct surveillance for
flashes of light associated with lunar meteorite impacts in real time (Dunham et al., 2000;
Cudnik et al., 2003). Since these initial successes, other meteor swarms have been shown
to produce lunar impacts (Yanagisawa et al., 2006; Ortiz et al. 2002, 2006).
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5. LUNAR IMPACT SELENOLOGY TODAY 23
NASA's Meteoroid Environment Office is conducting a survey of meteoroids striking the
lunar surface. Rates and distribution of impactors, shower and sporadic, have been discussed
by Cooke et al. (2007). However light flashes can be caused spuriously by a number of
factors including camera noise, cosmic rays, glints coming from space debris and satellites,
and terrestrial meteorites with trajectories toward the observer. Methods have been
developed by various groups that are intended to prevent spurious flashes being interpreted
as being genuine (Lena and Evans, 2008; Lena, 2009). The standard approach is to have an
impact recorded simultaneously by at least two observers located a minimum of 20-30 km
from each other, or meet the following criteria: (a) The flash is confirmed by two or more
independent observers. The flash on several subsequent video frames and exhibits a
decreasing light curve. There is no indication of flash movement. (b) The flash lasts 3 or
more video frames and exhibits a decreasing light curve. The flash is obvious in all frames
and there is no indication of flash movement. (c) The flash lasts 2 frames. It is easily
identifiable (bright) in the second frame and there is no indication of flash movement. After
the successful lunar monitoring experience of the 1999 and 2001 Leonids, a systematic
search and detection for sporadic impact flashes was conducted by Ortiz et al. (2006).
During a video monitoring carried out on February 11th 2011, Sposetti and Iten detected a
simultaneous flash of light on the rim of the lunar disk and preliminary results have been
presented in a previous work (cf. Sposetti, 2011 and the corresponding video animation
therein). In this article we report our final analysis and further conclusions that can be drawn
from the data.
2. Instrumental setup
Two specific instrumental setups were used for the lunar impact flash survey. The telescopes
consisted of a Borg 125 mm ED refractor and a 280 mm Schmidt–Cassegrain reflector
equipped with high sensitivity WAT-902H2 Ultimate CCD video cameras. Further data
concerning the two observatories are reported in Table 1. The distance between them is 12.9
km, measured with Google Earth.
3. Time of the flash
A time stamp was added to each video using a time inserter. The time of the flash was
determined to be 20:36:58.365 UTC ± 0.010s by Iten (maximum intensity of half-frame no.
109116 of the original AVI file). The frame was deinterlaced (cf. Fig.1).The corresponding
time of the flash in Sposetti’s video was determined to be 20:36:58.360 UTC ± 0.020s
(maximum intensity of frame no. 258556 of the original AVI file). This result matches very
well the time of occurrence of the flash in Iten’s AVI.
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9. LUNAR IMPACT SELENOLOGY TODAY 23
frame of the maximum intensity, i.e. in the corresponding 40 ms interval. The intensities
of the stars were measured and evaluated over several frames. We used the V magnitude
values of the stars (Table 5). Because no stars brighter than the flash were found, our
photometric measurement must be taken with a certain degree of uncertainty. Hence, the
resulting V magnitude estimated from our computation is 8.1 ± 0.3. The corresponding
light curves for this event are also shown in Figs. 14 and 15. The light curve of the flash
was traced two times. First we used individual frames of 40 ms integration (see Fig. 14).
The resulting curve gives a first idea of the evolution of the flash over time. A better
result can be obtained by deinterlacing the frames into their two fields, which yields a
doubled time resolution and a better light curve (see Fig. 15).
8. Results and discussion
The whole duration of the flash corresponds to 0.10 s ± 0.02 s in Sposetti’s video. We
observe that the half-frame of maximum intensity was preceded by an half-frame
showing about one-third of the maximum intensity. Also note that Iten's light curve of
the fields shows a strange up-and-down behaviour probably caused by some electronics
behaviour, we currently don’t understand. The brightness of the flash was estimated to
8.1 magV ± 0.3.
Specular reflection of sunlight from artificial satellites could cause very brief flashes.
However, the lack of a trail and the absence of another flash in the same frame or in other
frames indicate that the feature is not likely to be due to a satellite, nor to space debris. In
addition, the flash is present in a number of frames at a stationary position, which again
rules out cosmic rays, noise, or even artificial satellite glints. Besides, the positions of all
geostationary satellites were checked and none was within a few degrees of the Moon at
the impact time as seen from two observatories. The intensity of the flash is well above
the noise level, the event covers several video frames, and the final confirmation comes
from the fact that it was detected by two independent distant observers. Naturally
occurring dark limb meteoroid impact flashes currently are the subject of professional
research and professional-amateur cooperative observing campaigns. Artificial satellite
collision tests showed that much more energy can be converted to light than was
expected from standard collision theories (cf. Cudnik et al., 2003). The meteoroids that
caused the observed 1999 lunar Leonid impacts may be smaller by one or two orders of
magnitude than previously indicated, making them more compatible with the expected
Leonid stream size/mass distribution. Numerical simulations have determined that a
page 6
10. LUNAR IMPACT SELENOLOGY TODAY 23
magnitude 3 flash could be produced by an object of 3 kg mass travelling at the Leonid
impact velocity of 72 km s-1 (cf. Cudnik et al., 2003 and references therein). However,
the meteoroidal mass can only be estimated if the optical efficiency is known, which is
the fraction of the kinetic energy that is emitted in the visible. Bellot-Rubio et al. (2000a)
provide an analytic model for determining the luminous energy reaching the Earth from
lunar meteor impacts viewed at various angles. Numerical simulations of the impact of a
cometary projectile into solid granite at 72 km s-1 yield a luminous efficiency of (1–2) x
10− (Artemieva et al., 2000). Through comparison of several of the 1999 Leonid lunar
3
flashes with those of meteors observed on the ground, Bellot Rubio et al. (2000a, 2000b)
estimate the luminous efficiency of lunar impacts to be 2 x 10-3 with an uncertainty of 1
order of magnitude. They also compute a constant luminous efficiency of 2 x 10− for 3
these 72 km sec-1 impacts, i.e. two-thousands of the impact’s kinetic energy is converted
into light between 400 and 900 nm. However, the impact flash in this study probably
corresponds to a sporadic event because no major meteor showers were active or exhibit
favourable impact geometry on the impact date. Hence, the luminous efficiency may be
very different between sporadic meteoroids and Leonid-Perseid impactors regarded in
previous works (cf. Ortiz et al., 2002; Yanagisawa et al., 2006; Cudnik et al., 2003). In
this study, the same formalism and equations as in the works by Bellot Rubio et al.
(2000), Ortiz et al. (2002), and Carbognani (2000) was followed, including the kinetic
energy that is translated into impactor mass assuming a typical sporadic impactor speed.
According to the statistics of a large meteoroid orbit database (Steel, 1996) this speed is
approximately 20.2 km s-1 on Earth and 16.9 km s -1 on the Moon, after correcting for the
different escape velocities of the Earth and the Moon.
If v is the speed of the meteoroid of mass M, the kinetic energy of the body is given by:
(1)
The average magnitude of the flash observed from Earth is given by :
(2)
where τ the fraction of the kinetic energy converted to optical radiation and dTL the
is
Earth-Moon distance. Moreover, m o = - 26.8 and So= 1.36 x 103 W m-2 are the apparent
magnitude of the Sun and the solar constant, respectively.
page 7
11. LUNAR IMPACT SELENOLOGY TODAY 23
Therefore the following equation is used :
(3)
with
(4)
where M is measured in grams and the quantities v (velocity) and ∆t (duration of the
flash) are known. From the scaling law of Gault the diameter of the crater that is formed
is given approximately by:
(5)
where Ec is the kinetic energy of the meteoroid measured in Joules, while D is the
diameter of the crater in meters.
Moreover a short routine provided by Melosh and Beyer (1999) was used to evaluate the
scaling equations to determine the diameter of a crater given details on the nature of the
projectile, conditions of impact, and state of the target. The transient crater diameter is
evaluated by three independent methods, yield scaling, pi-scaling and Gault's semi-
empirical relations supplemented by rules on how crater size depends on gravity and
angle of impact. Assuming a luminous efficiency of order 2 x10 -3, the mass required to
generate the signal of the February 11th impact is 5 kg if we adopt the average velocity of
sporadic meteoroids (16.9 km s -1). The diameter of the crater formed on the lunar
surface can be estimated using Gault’s formula for craters of less than 100 m in diameter
formed in loose soil or regolith (cf. Melosh, 1989). The parameters used in the
calculation are the projectile density (2000 kg m -3), the target density (2000 kg m -3), the
impact velocity (16.9 km s -1), and the meteoroid mass previously inferred. The diameter
of the crater was thus calculated to be 4.5 m. Based on the above data and assuming a
spherical projectile the diameter of the impactor was inferred to be approximately 8 cm.
It stroke the target with an energy of about 8 x 107 Joules. However, the kinetic energy
is only affected by the luminous efficiency adopted. According to numerical models
(Nemtchinov et al., 1998; Melosh et al., 1993) or hypervelocity impact flash experiments
(Ernst and Schultz, 2005; Kadono and Fujiwara, 1996; Eichhorn, 1975), the luminous
efficiency of 2 x 10 -3 is already an optimistically high value. Besides, the value 2 x 10 -3
was derived from 71 km s -1 impacts, whereas at 16.9 km s -1, a different luminous
page 8
12. LUNAR IMPACT SELENOLOGY TODAY 23
efficiency would be expected. According to Ortiz et al. (2006), for sporadic impact
flashes on the Moon a luminous efficiency of 2 x 10 -2 is expected, yielding a mass of the
impactor of considerably less than 5 kg. In this case, assuming the same parameters as
those used in the previous computation, the impact flash appears to have been produced
by a 0.5 kg body with a diameter of approximately 6 cm when assuming a spherical
projectile. Using Gault’s scaling law in regolith for crater sizes, the size of the lunar
impact crater was computed to be 4 m. This value is similar for different impact angles of
the meteoroid. Using the Pi-scaled law for transient craters, the final crater is a simple
crater with a rim-to-rim diameter of 3.9 m. This impactor would strike the target with an
energy of 3.23 x 107 Joules (corresponding to 7.72 x 10 -9 Megatons). The results show
that the meteoroid is likely to range in size from about 6 to 8 cm in diameter producing a
crater of about 4-5 m in diameter. Figure 16 (WAC M102722785 ME) shows the region
of interest, determined in this work. The positioning uncertainty is fairly large because
the event occurred near the limb of the lunar disk where especially longitude uncertainty
is large. The Lunar Reconaissance orbiter (LRO) is continuously acquiring new images.
Hence, it will be interesting to compare LRO high resolution images (NAC images with
their resolution of ~1 m on the ground) of the impact area taken before and after the
event. Also if the impact region can be large, the high resolution of the NAC images
would in principle allow the detection of the small crater.
9. Summary and Conclusion
In this study we have described a lunar impact detected simultaneously from two
independent video recordings. The meteoroidal impact occurred at 20:36:58.360 UTC ±
0.020s on February 11, 2011. We have examined the flash characteristics in order to
exclude further lunar flash sources, e.g. cosmic rays, noise, meteors and artificial satellite
glints. The selenographic coordinates of the lunar impact flash are determined to 88° ± 2°
W and 16° ± 1° S, and the flash had a V magnitude of 8.1 ± 0.3. The duration of the
flash corresponds to 0.10 s ± 0.02 s in Sposetti's video. The mass of the impactor is
estimated to have been 5 kg based on a nominal model with conversion efficiency from
kinetic to optical energy of 2x 10 -3.
The examined impact flash probably corresponds to a sporadic event because no major
meteor showers were active or exhibit favourable impact geometry on the impact date.
Based on a modelling analysis, the mass of the impactor is estimated to has been 0.5 kg
assuming a luminous efficiency of 2×10 -2.
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13. LUNAR IMPACT SELENOLOGY TODAY 23
The results show that the meteoroid is likely to range in size from about 6 to 8 cm in
diameter and produced a crater of about 4-5 m in diameter. Future high-resolution
orbital data, e.g., from LRO spacecraft (NAC images) could allow the detection of the
small crater.
Acknowledgments: We are grateful to Gerhard Dangl and Jan Manek for their valuable
comments and suggestions.
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Figure 1. Video by Iten (flash detection).
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Figure 2. Celestial situation at the moment of the detection as seen from Sposetti’s
observatory.
Figure 3. The Flash and the two stars.
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Figure 4. Note in the above image that F lies just inside the lunar border. There is
also a very small parallax shift of the A star relative to the Moon border (in the
vertical direction of the image) of 5arcsec (about 2 pixels) because of the two distant
observatories.
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Figure 5. The flash at its maximum, 5x enlarged.
Figure 6. The xy-profiles-intensities of the flash at its maximum.
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Figure 7a. Image after application of a polynomial fit in order to remove the high
gradient.
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Figure 7b. Lunar map and the region in which the lunar flash was detected. North
is to the left and West to the bottom.
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Figure 8. A cosmic ray signature.
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Figure 9. A cosmic ray signature.
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Figure 10. A bright streak probably produced by a meteor.
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Figure 11. The track of the space debris FENGYUN 1C DEB(1999-025-AHJ) across
the Moon detected on August 08, 2008, at 19:05:06 UTC.
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30. LUNAR IMPACT SELENOLOGY TODAY 23
Figure 16. LRO imagery WAC M102722785 ME. North to the top and west to the
left. Approximately the image covers 10° N -18° N and 83° - 90° W, the region of the
examined lunar impact.
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Table 2 Moon data, at the moment of the detection, as seen from Sposetti’s
observatory.
Equatorial 2000: RA: 03h 42m 18s Dec: +22°09'00"
Horizon: Azim: 251°13'00" Alt: +47°07'17"
Visibility: Rise 10:43, Set 01:35 UTC
Transit time: 18:35 UTC
Phase: 55.63 %
Air mass: 1.36
Moon angular diameter: 00°30'25"
Moon distance: 392775.29 km
Moon altitude w/refraction: 47.1367°
Moon optical libration: l: -6.8811 b: -3.5348
Moon physical libration: l: -0.0183 b: -0.0129
Moon total libration: l: -6.8994 b: -3.5477
Moon position angle: -14.0966°
Moon phase angle: 83.5343°
Moon position angle of bright limb: 257.5143°
Sidereal time: 06:39
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Table 3. xy-plane coordinates of the stars "A" and "B" and of the flash "F" (Fig. 3).
SPOSETTI ITEN
xF (pixels) 246.5 258.5
yF (pixels) 172.0 279.0
xA (pixels) 477.3 418.8
yA (pixels) 124.5 239.4
xB (pixels) 647.5 536.6
yB (pixels) 82.5 204.1
AB distance (pixels) 175.305562 122.975323
BF distance (pixels) 410.866462 288.029069
AF distance (pixels) 235.637200 165.138313
BF/AB 2.343716 2.342170
AF/AB 1.344151 1.342857
%error BF/AB 0.066
%error AF/AB 0.096
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Table 4. Star data from Centre de Données astronomiques de Strasbourg
(http://cdsarc.u-strasbg.fr).
STAR A STAR B STAR C
Name BD+21 508 HD 23159 HD 23327
Coord. J2000.0 03 43 31.12 +22 09 30.1 03 43 42.38 +22 04 16.3 03 45 07.43 +22 17 36.8
Spectral type F8 D F2 D F5 D
B 11.12 10.1 9.57
V 10.47 9.67 9.19
R 10.33 - -
J 9.09 8.41 8.18
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35. FLASH F STAR A STAR B STAR C
LUNAR IMPACT
SPOSETTI Signal minus Background 1409 200 300 500
Error ± - 50 50 100
ITEN Signal minus Background 378 - 100 110
Error ± - - 20 20
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F compared to A F compared to B F compared to C
Table 5. Intensities and magnitudes.
SPOSETTI Magnitude 8.35 8 8.05
Error ± 0.3 0.2 0.3
ITEN Magnitude - 8.23 7.84
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Error ± - 0.3 0.2