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.
IMAGE ACQUISITION IN AN UNDERWATER VISION SYSTEM WITH NIR AND VIS ILLUMINATIONcsandit
The paper describes the image acquisition system able to capture images in two separated
bands of light, used to underwater autonomous navigation. The channels are: the visible light
spectrum and near infrared spectrum. The characteristics of natural, underwater environment
were also described together with the process of the underwater image creation. The results of
an experiment with comparison of selected images acquired in these channels are discussed.
This document summarizes the results of a sub-mm survey of the Carina Nebula complex conducted with the LABOCA instrument on the APEX telescope. The survey mapped an area of 1.25° × 1.25° at 870 μm, revealing the morphology and distribution of cold dust clouds with masses down to a few solar masses. The total mass of clouds detected is estimated to be around 60,000 M☉. The cloud morphologies range from large clouds of several thousand solar masses to small diffuse clouds of only a few solar masses. The distribution of sub-mm emission generally agrees with Spitzer 8 μm maps, identifying clouds interacting with massive stars as well as infrared dark clouds. The survey provides crucial
The document discusses satellite communication systems. It provides background on the history of satellite communications beginning in 1945. It then describes different types of satellite systems including geostationary, low earth orbit (LEO), and medium earth orbit (MEO) systems. Finally, it discusses key concepts for satellite systems such as localization, handover procedures, and examples of operational LEO and MEO networks.
1) The EPOXI mission flew by comet Hartley 2 in 2010, obtaining over 105 images and spectra.
2) Hartley 2 has an unusually small but very active bi-lobed nucleus with dimensions of 2.33 km and a rotation period of about 18 hours.
3) The nucleus shows substantial differences in volatile composition between its lobes and waist region.
Deep space communication involves transmitting data to and from satellites and spacecraft beyond Earth's atmosphere. It utilizes a global network of antennas to acquire telemetry from spacecraft, transmit commands, and gather science data across vast distances in space. The first deep space communication stations were established in the late 1950s and 1960s to support early US space missions. Today's deep space network, operated by NASA and ESA, employs large radio antennas around the world to communicate with missions throughout the solar system and gain new insights into the wider universe through radio astronomy observations.
1) The document presents a new hybrid seismic attribute called average SD that combines different spectral bands of frequencies to enhance identification of geological features from seismic data.
2) Average SD attributes are generated by averaging three frequency bands around a dominant frequency determined through tuning thickness analysis, which helps reduce noise and interference from other frequencies.
3) Using average SD attributes to calculate similarity attributes improves detection of thin channels compared to using normal amplitude, as it is less sensitive to amplitude changes and reduces noise. The hybrid approach enhances interpretation of both shallow and deep geological features.
The nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
This presentation was made for my 2nd year 2nd term course.
Me and my friend gave this presentation.
We are very much interested in cosmology and space program.
**If you want the script of this presentation leave a message in LinkedIn
IMAGE ACQUISITION IN AN UNDERWATER VISION SYSTEM WITH NIR AND VIS ILLUMINATIONcsandit
The paper describes the image acquisition system able to capture images in two separated
bands of light, used to underwater autonomous navigation. The channels are: the visible light
spectrum and near infrared spectrum. The characteristics of natural, underwater environment
were also described together with the process of the underwater image creation. The results of
an experiment with comparison of selected images acquired in these channels are discussed.
This document summarizes the results of a sub-mm survey of the Carina Nebula complex conducted with the LABOCA instrument on the APEX telescope. The survey mapped an area of 1.25° × 1.25° at 870 μm, revealing the morphology and distribution of cold dust clouds with masses down to a few solar masses. The total mass of clouds detected is estimated to be around 60,000 M☉. The cloud morphologies range from large clouds of several thousand solar masses to small diffuse clouds of only a few solar masses. The distribution of sub-mm emission generally agrees with Spitzer 8 μm maps, identifying clouds interacting with massive stars as well as infrared dark clouds. The survey provides crucial
The document discusses satellite communication systems. It provides background on the history of satellite communications beginning in 1945. It then describes different types of satellite systems including geostationary, low earth orbit (LEO), and medium earth orbit (MEO) systems. Finally, it discusses key concepts for satellite systems such as localization, handover procedures, and examples of operational LEO and MEO networks.
1) The EPOXI mission flew by comet Hartley 2 in 2010, obtaining over 105 images and spectra.
2) Hartley 2 has an unusually small but very active bi-lobed nucleus with dimensions of 2.33 km and a rotation period of about 18 hours.
3) The nucleus shows substantial differences in volatile composition between its lobes and waist region.
Deep space communication involves transmitting data to and from satellites and spacecraft beyond Earth's atmosphere. It utilizes a global network of antennas to acquire telemetry from spacecraft, transmit commands, and gather science data across vast distances in space. The first deep space communication stations were established in the late 1950s and 1960s to support early US space missions. Today's deep space network, operated by NASA and ESA, employs large radio antennas around the world to communicate with missions throughout the solar system and gain new insights into the wider universe through radio astronomy observations.
1) The document presents a new hybrid seismic attribute called average SD that combines different spectral bands of frequencies to enhance identification of geological features from seismic data.
2) Average SD attributes are generated by averaging three frequency bands around a dominant frequency determined through tuning thickness analysis, which helps reduce noise and interference from other frequencies.
3) Using average SD attributes to calculate similarity attributes improves detection of thin channels compared to using normal amplitude, as it is less sensitive to amplitude changes and reduces noise. The hybrid approach enhances interpretation of both shallow and deep geological features.
The nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
This presentation was made for my 2nd year 2nd term course.
Me and my friend gave this presentation.
We are very much interested in cosmology and space program.
**If you want the script of this presentation leave a message in LinkedIn
This document summarizes research analyzing data from the Voyager spacecraft regarding diffuse Lyman-alpha emission from the Milky Way galaxy. The analysis of Voyager Ultraviolet Spectrograph data from 1993 to 2011 revealed:
1) An excess of Lyman-alpha emission above what could be explained by local sources like the heliospheric glow, coinciding with regions of star formation along the Galactic Plane.
2) The background spectra of the UVS detectors increased constantly over time rather than decreasing as expected, likely due to energetic particles.
3) Comparison of the Lyman-alpha brightness data to a radiative transfer model showed an excess of a few Rayleigh coinciding with H-alpha bright star
~~ Hubble discovers ~~ ^^ a new moon ^^ around neptune from nasa at www.googl...Deepak Somaji Sawant
Mark Showalter of the SETI Institute discovered a new moon orbiting Neptune while studying faint arcs in images from the Hubble Space Telescope. The moon, designated S/2004 N 1, is estimated to be no more than 12 miles across, making it the smallest known moon of Neptune. Showalter tracked the movement of the moon over more than 150 archival Hubble images taken between 2004 and 2009. He determined it orbits about 65,400 miles from Neptune and completes one revolution every 23 hours.
This document summarizes observations from the Cassini spacecraft of a giant thunderstorm on Saturn in late 2010 and early 2011. The storm produced lightning at a rate over an order of magnitude higher than previous storms, with peak rates over 10 flashes per second. It originated at a latitude of 32° north and grew to a size comparable to Great White Spots, with a latitudinal extension of over 10,000 km. Unlike storms on Earth, the total power of this storm was comparable to Saturn's total emitted power. The storm drifted westward with the winds and eventually wrapped around the entire planet by February 2011.
This document summarizes a presentation about satellite communication. It discusses the basic concept of a communication satellite, how satellites are used as relay stations to transmit signals between Earth stations, and the different types of satellite orbits including geostationary, low Earth, and medium Earth orbits. It also covers topics like inter-satellite links, routing between satellites, common modulation techniques, and recent developments in satellite communication technology.
The document discusses the cosmic dawn and reionization period in the early universe. It describes the evolution from the dark ages after recombination to the epoch of reionization around z=6-20. Key aspects discussed include understanding the sources and sinks of ionizing photons that drove reionization, and challenges in modeling this period due to the large parameter space and scales involved, from single stars to the entire universe. Seminumerical simulations are presented as an efficient method to model reionization and predict 21cm signals.
The document discusses the history and types of satellite communications. It describes how the first artificial satellite used for communications was Echo 1, launched in 1960. It then discusses the development of active communications satellites like Telstar and the first geostationary satellite, Syncom 3. Finally, it summarizes the use of low Earth orbit satellites and Molniya orbits as alternatives to geostationary satellites for high latitude communications.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across Cepheus.
Satellite communications systems exist because radio waves travel in straight lines, requiring a repeater in space to convey signals over long distances. The document provides an overview of satellite communication systems, including different types of satellite orbits like geostationary and low earth orbits. It also covers key components of satellite systems like the space segment containing satellites, the ground segment containing earth stations, and the control segment for monitoring satellites. Link budgets are used to calculate the carrier-to-noise ratio in satellite links based on factors like transmitted power, gains, losses, and noise power.
Beyond the Kuiper Belt Edge: New High Perihelion Trans-Neptunian Objects With...Sérgio Sacani
We are conducting a survey for distant solar system objects beyond the Kuiper
Belt edge ( 50 AU) with new wide-field cameras on the Subaru and CTIO tele-
scopes. We are interested in the orbits of objects that are decoupled from the
giant planet region in order to understand the structure of the outer solar sys-
tem, including whether a massive planet exists beyond a few hundred AU as first
reported in Trujillo and Sheppard (2014). In addition to discovering extreme
trans-Neptunian objects detailed elsewhere, we have found several objects with
high perihelia (q > 40 AU) that differ from the extreme and inner Oort cloud
objects due to their moderate semi-major axes (50 < a < 100 AU) and eccen-
tricities (e . 0.3). Newly discovered objects 2014 FZ71 and 2015 FJ345 have
the third and fourth highest perihelia known after Sedna and 2012 VP113, yet
their orbits are not nearly as eccentric or distant. We found several of these high
perihelion but moderate orbit objects and observe that they are mostly near Nep-
tune mean motion resonances and have significant inclinations (i > 20 degrees).
These moderate objects likely obtained their unusual orbits through combined
interactions with Neptune’s mean motion resonances and the Kozai resonance,
similar to the origin scenarios for 2004 XR190. We also find the distant 2008
ST291 has likely been modified by the MMR+KR mechanism through the 6:1
Neptune resonance. We discuss these moderately eccentric, distant objects along
with some other interesting low inclination outer classical belt objects like 2012
FH84 discovered in our ongoing survey.
An actively accreting massive black hole in the dwarf starburst galaxy henize...Sérgio Sacani
1) Henize 2-10 is a nearby dwarf galaxy undergoing an extreme starburst, forming stars 10 times faster than the Large Magellanic Cloud despite similar masses.
2) Observations reveal a compact central radio source that is coincident with a point source emitting hard X-rays, indicating an actively accreting massive black hole.
3) The mass of the black hole is estimated to be around 1 million solar masses. This suggests that massive black holes can form in dwarf galaxies and their early Universe counterparts.
This document summarizes a study of the young star cluster IC 5146. Optical and near-infrared photometry were obtained for over 700 stars in the region, including around the illuminating stars BD +46°3474 and the embedded variable star BD +46°3471. Around 100 emission-line stars brighter than R=20.5 were found, most in IC 5146. Spectroscopy of 38 stars found an average extinction of AV=3.0 mag. The age distribution of the emission-line stars was estimated from theoretical isochrones to have a median age of around 1 Myr.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
Rapid and extensive surface changes near titan’s equator evidence of april s...Sérgio Sacani
Rapid and extensive surface changes were detected on Titan's surface near its equator using Cassini's Imaging Science Subsystem. In October 2010, a large region spanning over 500,000 square kilometers darkened, most likely due to widespread methane rainfall from a large low-latitude cloud system observed in late September. By January 2011, some but not all of the darkened area had reverted back to its original brightness. This suggests that seasonal precipitation may carve the dry channels seen at Titan's low latitudes.
The document analyzes GPS radio occultation data from six COSMIC satellites to characterize global ionospheric scintillation. Statistical analysis was performed on 1-second S4 measurements from the satellites over 12 months to determine the latitude, longitude, local time, and altitude distributions of scintillation in the F and E regions of the ionosphere. Maps are presented showing the occurrence rate of scintillation events by month at different longitudes and latitudes, and by season at different local times and latitudes.
This document describes two algorithms for determining water depth from high-resolution satellite imagery: a standard linear transform algorithm and a new ratio transform algorithm. The linear transform requires tuning five parameters and does not work for very low albedo bottoms, while the ratio transform requires tuning only two parameters and can handle low albedo features. Both algorithms were tested on IKONOS imagery of two coral reef atolls in the Hawaiian Islands against lidar bathymetry data. The ratio transform performed as well as the linear transform and was more robust, stable between areas, and able to retrieve depths over 25m. However, it was also slightly noisier and had trouble resolving fine structures below 15-20m depth.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
The document summarizes research from images taken by the New Horizons spacecraft of Charon, Pluto's largest moon. The images reveal Charon has a reddish polar cap at its north pole. Thermal models show the pole experiences long periods of extreme cold temperatures due to Charon's high obliquity and long seasons. The researchers hypothesize that methane and other volatiles escaping from Pluto's atmosphere become cold-trapped at Charon's winter pole, where they are processed by radiation into non-volatile organic compounds that remain on the surface to form the red cap. Spectral and compositional evidence supports this mechanism of seasonal accumulation of photolyzed volatiles to explain Charon's unique polar color
1) The galaxy merger rate over cosmic time is a fundamental measure of galaxy evolution. Mergers are thought to drive galaxy assembly, rapid star formation, and the formation of spheroidal galaxies and supermassive black holes.
2) While simulations predict that the dark matter halo merger rate increases strongly with redshift, the theoretical predictions for the galaxy merger rate remain uncertain due to the complex relationship between galaxies and dark matter halos.
3) The paper aims to address this problem by calibrating three observational galaxy merger rate estimators - close galaxy pairs, G-M20 morphology, and asymmetry - using hydrodynamic merger simulations. This allows them to determine merger timescales and consistently apply them to observed merger fractions up to
The article discusses two gaseous regions discovered that have a chemical composition close to that of the early universe before the first stars formed. This finding demonstrates that metals dispersed unevenly throughout the universe, with implications for when the first generation of stars could have formed. The early universe began with hydrogen, helium, and trace amounts of lithium produced by Big Bang nucleosynthesis. Later, the first stars enriched and ionized the universe with heavier elements, though it appears this process was nonuniform based on the discovery of pockets of nearly pristine gas.
The small blue_straggler_star_population_in_the_dense_galactic_globular_clust...Sérgio Sacani
This document summarizes a study of blue straggler star (BSS) populations in the globular cluster NGC 6752. The study used high-resolution Hubble Space Telescope images of the cluster core and wide-field ground-based images covering the outer regions. A total of 28 BSS candidates were identified in the HST images, and an additional 15 BSS candidates were found in the outer regions from the ground-based images. The radial distribution of BSS will be analyzed to understand the dynamical evolution of the cluster.
This document summarizes research analyzing data from the Voyager spacecraft regarding diffuse Lyman-alpha emission from the Milky Way galaxy. The analysis of Voyager Ultraviolet Spectrograph data from 1993 to 2011 revealed:
1) An excess of Lyman-alpha emission above what could be explained by local sources like the heliospheric glow, coinciding with regions of star formation along the Galactic Plane.
2) The background spectra of the UVS detectors increased constantly over time rather than decreasing as expected, likely due to energetic particles.
3) Comparison of the Lyman-alpha brightness data to a radiative transfer model showed an excess of a few Rayleigh coinciding with H-alpha bright star
~~ Hubble discovers ~~ ^^ a new moon ^^ around neptune from nasa at www.googl...Deepak Somaji Sawant
Mark Showalter of the SETI Institute discovered a new moon orbiting Neptune while studying faint arcs in images from the Hubble Space Telescope. The moon, designated S/2004 N 1, is estimated to be no more than 12 miles across, making it the smallest known moon of Neptune. Showalter tracked the movement of the moon over more than 150 archival Hubble images taken between 2004 and 2009. He determined it orbits about 65,400 miles from Neptune and completes one revolution every 23 hours.
This document summarizes observations from the Cassini spacecraft of a giant thunderstorm on Saturn in late 2010 and early 2011. The storm produced lightning at a rate over an order of magnitude higher than previous storms, with peak rates over 10 flashes per second. It originated at a latitude of 32° north and grew to a size comparable to Great White Spots, with a latitudinal extension of over 10,000 km. Unlike storms on Earth, the total power of this storm was comparable to Saturn's total emitted power. The storm drifted westward with the winds and eventually wrapped around the entire planet by February 2011.
This document summarizes a presentation about satellite communication. It discusses the basic concept of a communication satellite, how satellites are used as relay stations to transmit signals between Earth stations, and the different types of satellite orbits including geostationary, low Earth, and medium Earth orbits. It also covers topics like inter-satellite links, routing between satellites, common modulation techniques, and recent developments in satellite communication technology.
The document discusses the cosmic dawn and reionization period in the early universe. It describes the evolution from the dark ages after recombination to the epoch of reionization around z=6-20. Key aspects discussed include understanding the sources and sinks of ionizing photons that drove reionization, and challenges in modeling this period due to the large parameter space and scales involved, from single stars to the entire universe. Seminumerical simulations are presented as an efficient method to model reionization and predict 21cm signals.
The document discusses the history and types of satellite communications. It describes how the first artificial satellite used for communications was Echo 1, launched in 1960. It then discusses the development of active communications satellites like Telstar and the first geostationary satellite, Syncom 3. Finally, it summarizes the use of low Earth orbit satellites and Molniya orbits as alternatives to geostationary satellites for high latitude communications.
This document summarizes star forming regions in the constellation of Cepheus. It describes several giant molecular cloud complexes located at various distances from the Sun, ranging from clouds within 500 pc to regions associated with the Perseus spiral arm at 2-3 kpc. Key regions discussed include the Cepheus Flare clouds below 500 pc, three OB associations (Cep OB2, Cep OB3, Cep OB4) located 600-900 pc away, and the well-known high mass star forming region S 140 located at 900 pc. Tables list molecular clouds and young stars identified in the Cepheus region. Maps show the distribution of clouds, extinction, and pre-main sequence stars across Cepheus.
Satellite communications systems exist because radio waves travel in straight lines, requiring a repeater in space to convey signals over long distances. The document provides an overview of satellite communication systems, including different types of satellite orbits like geostationary and low earth orbits. It also covers key components of satellite systems like the space segment containing satellites, the ground segment containing earth stations, and the control segment for monitoring satellites. Link budgets are used to calculate the carrier-to-noise ratio in satellite links based on factors like transmitted power, gains, losses, and noise power.
Beyond the Kuiper Belt Edge: New High Perihelion Trans-Neptunian Objects With...Sérgio Sacani
We are conducting a survey for distant solar system objects beyond the Kuiper
Belt edge ( 50 AU) with new wide-field cameras on the Subaru and CTIO tele-
scopes. We are interested in the orbits of objects that are decoupled from the
giant planet region in order to understand the structure of the outer solar sys-
tem, including whether a massive planet exists beyond a few hundred AU as first
reported in Trujillo and Sheppard (2014). In addition to discovering extreme
trans-Neptunian objects detailed elsewhere, we have found several objects with
high perihelia (q > 40 AU) that differ from the extreme and inner Oort cloud
objects due to their moderate semi-major axes (50 < a < 100 AU) and eccen-
tricities (e . 0.3). Newly discovered objects 2014 FZ71 and 2015 FJ345 have
the third and fourth highest perihelia known after Sedna and 2012 VP113, yet
their orbits are not nearly as eccentric or distant. We found several of these high
perihelion but moderate orbit objects and observe that they are mostly near Nep-
tune mean motion resonances and have significant inclinations (i > 20 degrees).
These moderate objects likely obtained their unusual orbits through combined
interactions with Neptune’s mean motion resonances and the Kozai resonance,
similar to the origin scenarios for 2004 XR190. We also find the distant 2008
ST291 has likely been modified by the MMR+KR mechanism through the 6:1
Neptune resonance. We discuss these moderately eccentric, distant objects along
with some other interesting low inclination outer classical belt objects like 2012
FH84 discovered in our ongoing survey.
An actively accreting massive black hole in the dwarf starburst galaxy henize...Sérgio Sacani
1) Henize 2-10 is a nearby dwarf galaxy undergoing an extreme starburst, forming stars 10 times faster than the Large Magellanic Cloud despite similar masses.
2) Observations reveal a compact central radio source that is coincident with a point source emitting hard X-rays, indicating an actively accreting massive black hole.
3) The mass of the black hole is estimated to be around 1 million solar masses. This suggests that massive black holes can form in dwarf galaxies and their early Universe counterparts.
This document summarizes a study of the young star cluster IC 5146. Optical and near-infrared photometry were obtained for over 700 stars in the region, including around the illuminating stars BD +46°3474 and the embedded variable star BD +46°3471. Around 100 emission-line stars brighter than R=20.5 were found, most in IC 5146. Spectroscopy of 38 stars found an average extinction of AV=3.0 mag. The age distribution of the emission-line stars was estimated from theoretical isochrones to have a median age of around 1 Myr.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
Rapid and extensive surface changes near titan’s equator evidence of april s...Sérgio Sacani
Rapid and extensive surface changes were detected on Titan's surface near its equator using Cassini's Imaging Science Subsystem. In October 2010, a large region spanning over 500,000 square kilometers darkened, most likely due to widespread methane rainfall from a large low-latitude cloud system observed in late September. By January 2011, some but not all of the darkened area had reverted back to its original brightness. This suggests that seasonal precipitation may carve the dry channels seen at Titan's low latitudes.
The document analyzes GPS radio occultation data from six COSMIC satellites to characterize global ionospheric scintillation. Statistical analysis was performed on 1-second S4 measurements from the satellites over 12 months to determine the latitude, longitude, local time, and altitude distributions of scintillation in the F and E regions of the ionosphere. Maps are presented showing the occurrence rate of scintillation events by month at different longitudes and latitudes, and by season at different local times and latitudes.
This document describes two algorithms for determining water depth from high-resolution satellite imagery: a standard linear transform algorithm and a new ratio transform algorithm. The linear transform requires tuning five parameters and does not work for very low albedo bottoms, while the ratio transform requires tuning only two parameters and can handle low albedo features. Both algorithms were tested on IKONOS imagery of two coral reef atolls in the Hawaiian Islands against lidar bathymetry data. The ratio transform performed as well as the linear transform and was more robust, stable between areas, and able to retrieve depths over 25m. However, it was also slightly noisier and had trouble resolving fine structures below 15-20m depth.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
The document summarizes research from images taken by the New Horizons spacecraft of Charon, Pluto's largest moon. The images reveal Charon has a reddish polar cap at its north pole. Thermal models show the pole experiences long periods of extreme cold temperatures due to Charon's high obliquity and long seasons. The researchers hypothesize that methane and other volatiles escaping from Pluto's atmosphere become cold-trapped at Charon's winter pole, where they are processed by radiation into non-volatile organic compounds that remain on the surface to form the red cap. Spectral and compositional evidence supports this mechanism of seasonal accumulation of photolyzed volatiles to explain Charon's unique polar color
1) The galaxy merger rate over cosmic time is a fundamental measure of galaxy evolution. Mergers are thought to drive galaxy assembly, rapid star formation, and the formation of spheroidal galaxies and supermassive black holes.
2) While simulations predict that the dark matter halo merger rate increases strongly with redshift, the theoretical predictions for the galaxy merger rate remain uncertain due to the complex relationship between galaxies and dark matter halos.
3) The paper aims to address this problem by calibrating three observational galaxy merger rate estimators - close galaxy pairs, G-M20 morphology, and asymmetry - using hydrodynamic merger simulations. This allows them to determine merger timescales and consistently apply them to observed merger fractions up to
The article discusses two gaseous regions discovered that have a chemical composition close to that of the early universe before the first stars formed. This finding demonstrates that metals dispersed unevenly throughout the universe, with implications for when the first generation of stars could have formed. The early universe began with hydrogen, helium, and trace amounts of lithium produced by Big Bang nucleosynthesis. Later, the first stars enriched and ionized the universe with heavier elements, though it appears this process was nonuniform based on the discovery of pockets of nearly pristine gas.
The small blue_straggler_star_population_in_the_dense_galactic_globular_clust...Sérgio Sacani
This document summarizes a study of blue straggler star (BSS) populations in the globular cluster NGC 6752. The study used high-resolution Hubble Space Telescope images of the cluster core and wide-field ground-based images covering the outer regions. A total of 28 BSS candidates were identified in the HST images, and an additional 15 BSS candidates were found in the outer regions from the ground-based images. The radial distribution of BSS will be analyzed to understand the dynamical evolution of the cluster.
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
Ages and stratigraphy of lunar mare basalts a synthesisSérgio Sacani
This document summarizes ages and stratigraphy of lunar mare basalts based on a synthesis of crater counting efforts over more than 10 years. The key points are:
1) Lunar volcanism was active for almost 3 billion years, starting around 3.9-4 billion years ago and ceasing around 1.2 billion years ago.
2) Most basalts erupted during the late Imbrian period around 3.6-3.8 billion years ago.
3) Significantly fewer basalts were emplaced during the Eratosthenian period.
4) Basalts of possible Copernican age have only been found in limited areas of Oceanus Procellarum.
This document summarizes a study that estimates the dynamical surface mass density between 1.5 and 4 kpc from the Galactic plane using kinematics of thick disk stars. The authors derive an exact analytical expression for the surface density based on assumptions about the stellar population and Galactic potential. Their expression matches expectations of visible mass alone, with no evidence for additional dark matter required. They extrapolate a local dark matter density of 0±1 mM⊙ pc−3, excluding all current spherical dark matter halo models at over 4σ confidence. Only a highly prolate dark matter halo could potentially reconcile the observations with models, but this is unlikely according to ΛCDM.
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.
A Morphological and Spatial Analysis of Volcanoes on VenusSérgio Sacani
Venus is home to many thousands of volcanic landforms that range in size from much less than 5 km to well over 100 km in diameter. Volcanism is clearly a major, widespread process on Venus, and is a principal expression of the planet's secular loss of interior heat. Without sufficient in situ data to clearly determine its internal structure, we can use the morphological and spatial properties of volcanoes across the planet to help place constraints on our understanding of the volcanic characteristics and history of Venus. With the Magellan synthetic-aperture radar full-resolution radar map left- and right-look global mosaics at 75 m-per-pixel resolution, we developed a global catalog of volcanoes on Venus that contains ∼85,000 edifices, ∼99% of which are <5 km in diameter. We find that Venus hosts far more volcanoes than previously mapped, and that although they are distributed across virtually the entire planet, size–frequency distribution analysis reveals a relative lack of edifices in the 20–100 km diameter range, which could be related to magma availability and eruption rate. Through spatial density analysis of volcanoes alongside assessments of geophysical data sets and proximal tectonic and volcanic structures, we report on the morphological and spatial patterns of volcanism on Venus to help gain new insights into the planet's geological evolution
This document discusses planetary and tidal wave oscillations observed in ionospheric sporadic E layers over Tehran, Iran. Wavelet analysis was used to examine time series data of critical frequency (foEs) and virtual height (h'Es) of sporadic E layers from July 2006 to June 2007. The results show:
1) Diurnal (24-hour) and semidiurnal (12-hour) oscillations were present in all seasons for both foEs and h'Es. Terdiurnal (8-hour) variations were also observed.
2) Planetary wave oscillations of around 2, 4, 6, and 10 days were observed, with maximum activity during equinox seasons.
3)
1. The spectrum of the bright Kuiper Belt object 2005 FY9 is dominated by methane absorption features in the near-infrared region. However, the methane absorption lines are significantly broader than seen on any other solar system body, indicating unusually long optical path lengths through methane grains on 2005 FY9, estimated to be around 1 cm in size.
2. In addition to methane, the spectrum also shows clear evidence for ethane, which is expected to form from UV photolysis of methane. No evidence is found for nitrogen or carbon monoxide, both known to be present on Pluto.
3. The differences between 2005 FY9's spectrum and those of Pluto and 2003 UB313 are suggested
X-Ray Luminous Supernovae: Threats to Terrestrial BiospheresSérgio Sacani
This document discusses the threat posed by X-ray luminous supernovae (SNe) to terrestrial biospheres. It analyzes observations of 31 X-ray luminous SNe from various telescopes. It finds that SNe showing strong circumstellar interaction, like Type IIn explosions, have significantly larger ranges of influence than previously thought, with lethal consequences up to around 50 parsecs away. The sustained high X-ray luminosity from these SNe leads to large doses of ionizing radiation over formidable distances. This poses a distinct threat to terrestrial biospheres and tightens the boundaries of the Galactic Habitable Zone. Follow-up X-ray observations of interacting SNe are needed to better understand the physical nature and
NEAR-IR SPECTRAL OBSERVATIONS OF THE DIDYMOS SYSTEM - DAILY EVOLUTION BEFORE ...Sérgio Sacani
1) Near-IR spectroscopic observations were taken of the Didymos system daily before and after the DART impact to study the evolution of the ejecta cloud.
2) The spectral features remained consistent with an S-type classification, confirming that Didymos and Dimorphos are composed of similar silicate material. This supports models of binary asteroid formation via rotational breakup.
3) In the first 38 hours after impact, the spectral slope decreased as coarser ejecta dominated but then increased again as the ejecta cloud dispersed, returning to the pre-impact slope within a week. No "fresh" non-weathered material was detected from Dimorphos' subsurface.
Peters et al_a_search_for_large-scale_effects_of_ship_emissions_on_clouds_and...www.thiiink.com
Introduction
Ship tracks are widely seen as one of the most prominent
manifestations of anthropogenic aerosol indirect effects
(AIEs), or the change in cloud properties by anthropogenic
aerosols serving as cloud condensation nuclei. A very uncertain
and scientifically interesting question, however, is about
the climatically relevant large-scale forcing by AIEs due to
ship emissions.
In the past decades, a whole suite of AIE-hypotheses has
been put forward of which the “Twomey-effect”, or first AIE,
is the most prominent. For this effect, an increase in available
cloud condensation nuclei (CCN) eventually leads to
more and smaller cloud droplets if the liquid water content of
the respective cloud remains constant. More cloud droplets
increase the total droplet surface area by which the cloud
albedo is enhanced; an effect which was put into the general
context of anthropogenic pollution by Twomey (1974). Other
AIE-hypotheses include effects on cloud lifetime (Albrecht,
1989; Small et al., 2009) or cloud top height (Koren et al.,
2005; Devasthale et al., 2005). Especially the latter hypotheses
are far from being verified (e.g. Stevens and Feingold,
2009). In total, AIEs are subject to the largest uncertainties
Published by Copernicus Publications on behalf of the European Geosciences Union.
5986 K. Peters et al.: Aerosol indirect effects from shipping emissions
of all radiative forcing (RF) components of the Earth System,
when it comes to assessing human induced climate change
(Forster et al., 2007). However, there exists broad consensus
that on global average, AIEs have a cooling effect on the
Earth System with the most recent multi-model estimate being
−0.7 ± 0.5 W m−2
(Quaas et al., 2009).
This document introduces the VLT-FLAMES Tarantula Survey, which obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. The survey aims to detect massive binary systems through variations in radial velocities and to characterize the properties of O- and B-type stars, addressing questions about stellar and cluster evolution. Spectral classifications are provided for newly discovered emission-line stars, including a new Wolf-Rayet star. The survey data and reduction procedures are overviewed, and upcoming analyses of the massive star properties are announced.
A uranian trojan_and_the_frequency_of_temporary_giant_planet_co_orbitalsSérgio Sacani
1) Researchers detected a 60 km diameter object called 2011 QF99 that orbits the Sun in a 1:1 resonance with Uranus, never straying far from Uranus' Lagrangian point 60 degrees ahead of it (L4).
2) Numerical simulations show 2011 QF99 oscillating around the L4 point for over 70,000 years before transitioning to other co-orbital behavior and eventually becoming unstable within 1 million years.
3) Based on these simulations and estimates of supply from the trans-Neptunian region, the researchers calculate that temporarily around 0.4% of Centaurs should be Uranian co-orbitals and 2.8% should be Neptun
This document summarizes an observational study of 92 southern stars using near-infrared interferometry to search for hot exozodiacal dust. The study found an 11% detection rate of bright dust, with 9 confirmed and 3 tentative detections. The detection rate decreased for later spectral type stars and increased with stellar age. No correlation was found between the presence of cold dust and hot dust. Spectral analysis suggested the dust is extremely hot or emission is dominated by scattered light in most cases. The results provide insights into the prevalence and properties of dust near the habitable zones of other stars.
Our deep, wide-field imaging of M101 and its surrounding environment reveals:
1) M101's disk extends to nearly 25 arcminutes (50 kpc), three times the measured optical radius, with an asymmetric plume of light to the northeast following the extended HI disk.
2) This outer plume has very blue colors, suggesting a somewhat evolved young stellar population, while another redder spur is detected to the east.
3) No evidence is found of very extended tidal tails around M101 or its companions despite signs of past interactions shaping M101's asymmetry.
4) The detection of starlight at such large radii allows studying the stellar populations and star formation histories in M101's outer disk
A Tale of 3 Dwarf Planets: Ices and Organics on Sedna, Gonggong, and Quaoar f...Sérgio Sacani
The dwarf planets Sedna, Gonggong, and Quaoar are interesting in being somewhat smaller than
the methane-rich bodies of the Kuiper Belt (Pluto, Eris, Makemake), yet large enough to be
spherical and to have possibly undergone interior melting and differentiation. They also reside
on very different orbits, making them an ideal suite of bodies for untangling effects of size and
orbit on present day surface composition. We observed Sedna, Gonggong, and Quaoar with the
NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were
observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 μm. Quaoar was
additionally observed at 10x higher spectral resolution from 0.97 to 3.16 μm using mediumresolution gratings. Sedna’s spectrum shows a large number of absorption features due to ethane
(C2H6), as well as acetylene (C2H2), ethylene (C2H4), H2O, and possibly minor CO2.
Gonggong’s spectrum also shows several, but fewer and weaker, ethane features, along with
stronger and cleaner H2O features and CO2 complexed with other molecules. Quaoar’s prism
spectrum shows even fewer and weaker ethane features, the deepest and cleanest H2O features, a
feature at 3.2 μm possibly due to HCN, and CO2 ice. The higher-resolution medium grating
spectrum of Quaoar reveals several overtone and combination bands of ethane and methane
(CH4). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions
between 2.7 and 3.6 μm indicative of complex organic molecules. The suite of light
hydrocarbons and complex organic molecules are interpreted as the products of irradiation of
methane. The differences in apparent abundances of irradiation products among these three
similarly-sized bodies are likely due to their distinctive orbits, which lead to different timescales
of methane retention and to different charged particle irradiation environments. In all cases,
however, the continued presence of light hydrocarbons implies a resupply of methane to the
2
surface. We suggest that these three bodies have undergone internal melting and geochemical
evolution similar to the larger dwarf planets and distinct from all smaller KBOs. The feature
identification presented in this paper is the first step of analysis, and additional insight into the
relative abundances and mixing states of materials on these surfaces will come from future
spectral modeling of these data.
Small dust particles escaping from Pluto's moons Nix and Hydra could temporarily form a ring around Pluto due to impacts, but the solar radiation pressure would remove about half of 1 micrometer particles within a year by causing collisions with Pluto and its moons. Numerical simulations found that a tenuous ring with an optical depth of 6×10^-11 could be maintained by dust released from Nix and Hydra.
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 fornax deep_survey_with_vst_i_the_extended_and_diffuse_stellar_halo_of_ng...Sérgio Sacani
We have started a new deep, multi-imaging survey of the Fornax cluster, dubbed Fornax Deep
Survey (FDS), at the VLT Survey Telescope. In this paper we present the deep photometry inside
two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that
the core of the Fornax cluster is characterised by a very extended and diffuse envelope surrounding
the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (∼ 192 kpc)
from the galaxy center and down to μg ∼ 31 mag arcsec−2 in the g band. The deep photometry
allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399
and towards NGC 1387. By analyzing the integrated colors of this feature, we argue that it
could be due to the ongoing interaction between the two galaxies, where the outer envelope of
NGC 1387 on its east side is stripped away. By fitting the light profile, we found that exists a
physical break radius in the total light distribution at R = 10 arcmin (∼ 58 kpc) that sets the
transition region between the bright central galaxy and the outer exponential halo, and that the
stellar halo contributes for 60% of the total light of the galaxy (Sec. 3.5). We discuss the main
implications of this work on the build-up of the stellar halo at the center of the Fornax cluster.
By comparing with the numerical simulations of the stellar halo formation for the most massive
BCGs (i.e. 13 < logM200/M⊙ < 14), we find that the observed stellar halo mass fraction is
consistent with a halo formed through the multiple accretion of progenitors with stellar mass in
the range 108 − 1011 M⊙. This might suggest that the halo of NGC 1399 has also gone through
a major merging event. The absence of a significant number of luminous stellar streams and
tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early
formation epoch. Therefore, differently from the Virgo cluster, the extended stellar halo around
NGC 1399 is characterised by a more diffuse and well-mixed component, including the ICL.
Venus cloud discontinuity in 2022 The first long-term study with uninterrupte...Sérgio Sacani
This document summarizes observations of a cloud discontinuity on Venus made between December 2021 and July 2022 using multiple instruments. The key findings are:
1) The cloud discontinuity was tracked at the middle clouds of Venus for 109 continuous days, exhibiting consistent properties with previous observations including an orientation of 91°±8°, length of 4100±800 km, width of 500±100 km, and rotation period of 5.11±0.09 days.
2) Ultraviolet images on June 13-14, 2022 suggest the discontinuity may have reached the top of the clouds for around 21 hours, which would be the first observation of it at this altitude.
3) Over 300 images from multiple
High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019Sérgio Sacani
Imaging observations of Jupiter with high spatial resolution were acquired beginning in 2016, with a cadence of 53
days to coincide with atmospheric observations of the Juno spacecraft during each perijove pass. The Wide Field
Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) collected Jupiter images from 236 to 925 nm in 14
filters. The Near-Infrared Imager (NIRI) at Gemini North imaged Jovian thermal emission using a lucky-imaging
approach (co-adding the sharpest frames taken from a sequence of short exposures), using the M′ filter at 4.7 μm.
We discuss the data acquisition and processing and an archive collection that contains the processed WFC3 and
NIRI data (doi:10.17909/T94T1H). Zonal winds remain steady over time at most latitudes, but significant
evolution of the wind profile near 24°N in 2016 and near 15°S in 2017 was linked with convective superstorm
eruptions. Persistent mesoscale waves were seen throughout the 2016–2019 period. We link groups of lightning
flashes observed by the Juno team with water clouds in a large convective plume near 15°S and in cyclones near
35°N–55°N. Thermal infrared maps at the 10.8 micron wavelength obtained at the Very Large Telescope show
consistent high brightness temperature anomalies, despite a diversity of aerosol properties seen in the HST data.
Both WFC3 and NIRI imaging reveal depleted aerosols consistent with downwelling around the periphery of the
15°S storm, which was also observed by the Atacama Large Millimeter/submillimeter Array. NIRI imaging of
the Great Red Spot shows that locally reduced cloud opacity is responsible for dark features within the vortex. The
HST data maps multiple concentric polar hoods of high-latitude hazes.
11.the response of interplanetary medium to the geomagnetic storm of april 20...Alexander Decker
This document examines the behavior of the interplanetary medium during the geomagnetic storm that occurred between April 5-7, 2010. It analyzes data on the southward component of the Interplanetary Magnetic Field (Bz), Disturbance Storm Time index (Dst), solar wind speed, and the H and Z components of the Earth's magnetic field recorded at equatorial and polar stations. The storm had a sudden commencement phase when a strong solar wind compressed the magnetosphere, a main phase when Dst reached a minimum of -73nT, and a recovery phase as Bz and solar wind decreased. There was a sharp decrease in the H component across all latitudes during the storm in response to changes
Multi dimensional simulations_of_the_expanding_supernova_remnant_of_sn1987_aSérgio Sacani
Artigo descreve as mais novas simulações computacionais realizadas para se poder entender o funcionamento e a origem da remanescente de supernova SN1987A.
Study of Average Hourly Variations of Radio Refractivity Variations across So...iosrjce
The results of the diurnal variation of refractivity based on measurement of atmospheric pressure,
temperature and relative humidity made across some selected locations within Nigeria, Yola (90
11' N, 120
30'
E), Anyigba (70
45' N, 60
45' E), Lagos (60
27' N, 50
12' E), and Port-Harcourt (40
48'N, 70E), is presented in this
study. The study utilized three years of meteorological data measured from January 2010 to December 2013
using Vantage Pro 2 automatic weather station installed at each location. The average hourly variations of
refractivity in the dry season is largely as a result of the variations of the wet component (humidity) while the
average daily variations of surface radio refractivity in the rainy season is as a result of both the variations of
the dry (pressure) and wet (humidity) component of surface radio refractivity. It also observed that the values of
surface radio refractivity showed seasonal variations with high value during rainy season and low values
during dry season with an increase in the value of surface radio refractivity from minimum value of about
242N-units at Anyigba station to maximum value of about 384-N units at Lagos station. The diurnal variation of
refractivity of the troposphere is a function of local meteorology as observed from results obtained from the
study.
Similar to Lunar skylight polarization signal polluted by urban lighting (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
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.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
Main news related to the CCS TSI 2023 (2023/1695)Jakub Marek
An English 🇬🇧 translation of a presentation to the speech I gave about the main changes brought by CCS TSI 2023 at the biggest Czech conference on Communications and signalling systems on Railways, which was held in Clarion Hotel Olomouc from 7th to 9th November 2023 (konferenceszt.cz). Attended by around 500 participants and 200 on-line followers.
The original Czech 🇨🇿 version of the presentation can be found here: https://www.slideshare.net/slideshow/hlavni-novinky-souvisejici-s-ccs-tsi-2023-2023-1695/269688092 .
The videorecording (in Czech) from the presentation is available here: https://youtu.be/WzjJWm4IyPk?si=SImb06tuXGb30BEH .
Ivanti’s Patch Tuesday breakdown goes beyond patching your applications and brings you the intelligence and guidance needed to prioritize where to focus your attention first. Catch early analysis on our Ivanti blog, then join industry expert Chris Goettl for the Patch Tuesday Webinar Event. There we’ll do a deep dive into each of the bulletins and give guidance on the risks associated with the newly-identified vulnerabilities.
Driving Business Innovation: Latest Generative AI Advancements & Success StorySafe Software
Are you ready to revolutionize how you handle data? Join us for a webinar where we’ll bring you up to speed with the latest advancements in Generative AI technology and discover how leveraging FME with tools from giants like Google Gemini, Amazon, and Microsoft OpenAI can supercharge your workflow efficiency.
During the hour, we’ll take you through:
Guest Speaker Segment with Hannah Barrington: Dive into the world of dynamic real estate marketing with Hannah, the Marketing Manager at Workspace Group. Hear firsthand how their team generates engaging descriptions for thousands of office units by integrating diverse data sources—from PDF floorplans to web pages—using FME transformers, like OpenAIVisionConnector and AnthropicVisionConnector. This use case will show you how GenAI can streamline content creation for marketing across the board.
Ollama Use Case: Learn how Scenario Specialist Dmitri Bagh has utilized Ollama within FME to input data, create custom models, and enhance security protocols. This segment will include demos to illustrate the full capabilities of FME in AI-driven processes.
Custom AI Models: Discover how to leverage FME to build personalized AI models using your data. Whether it’s populating a model with local data for added security or integrating public AI tools, find out how FME facilitates a versatile and secure approach to AI.
We’ll wrap up with a live Q&A session where you can engage with our experts on your specific use cases, and learn more about optimizing your data workflows with AI.
This webinar is ideal for professionals seeking to harness the power of AI within their data management systems while ensuring high levels of customization and security. Whether you're a novice or an expert, gain actionable insights and strategies to elevate your data processes. Join us to see how FME and AI can revolutionize how you work with data!
OpenID AuthZEN Interop Read Out - AuthorizationDavid Brossard
During Identiverse 2024 and EIC 2024, members of the OpenID AuthZEN WG got together and demoed their authorization endpoints conforming to the AuthZEN API
HCL Notes and Domino License Cost Reduction in the World of DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-and-domino-license-cost-reduction-in-the-world-of-dlau/
The introduction of DLAU and the CCB & CCX licensing model caused quite a stir in the HCL community. As a Notes and Domino customer, you may have faced challenges with unexpected user counts and license costs. You probably have questions on how this new licensing approach works and how to benefit from it. Most importantly, you likely have budget constraints and want to save money where possible. Don’t worry, we can help with all of this!
We’ll show you how to fix common misconfigurations that cause higher-than-expected user counts, and how to identify accounts which you can deactivate to save money. There are also frequent patterns that can cause unnecessary cost, like using a person document instead of a mail-in for shared mailboxes. We’ll provide examples and solutions for those as well. And naturally we’ll explain the new licensing model.
Join HCL Ambassador Marc Thomas in this webinar with a special guest appearance from Franz Walder. It will give you the tools and know-how to stay on top of what is going on with Domino licensing. You will be able lower your cost through an optimized configuration and keep it low going forward.
These topics will be covered
- Reducing license cost by finding and fixing misconfigurations and superfluous accounts
- How do CCB and CCX licenses really work?
- Understanding the DLAU tool and how to best utilize it
- Tips for common problem areas, like team mailboxes, functional/test users, etc
- Practical examples and best practices to implement right away
Programming Foundation Models with DSPy - Meetup SlidesZilliz
Prompting language models is hard, while programming language models is easy. In this talk, I will discuss the state-of-the-art framework DSPy for programming foundation models with its powerful optimizers and runtime constraint system.
Monitoring and Managing Anomaly Detection on OpenShift.pdfTosin Akinosho
Monitoring and Managing Anomaly Detection on OpenShift
Overview
Dive into the world of anomaly detection on edge devices with our comprehensive hands-on tutorial. This SlideShare presentation will guide you through the entire process, from data collection and model training to edge deployment and real-time monitoring. Perfect for those looking to implement robust anomaly detection systems on resource-constrained IoT/edge devices.
Key Topics Covered
1. Introduction to Anomaly Detection
- Understand the fundamentals of anomaly detection and its importance in identifying unusual behavior or failures in systems.
2. Understanding Edge (IoT)
- Learn about edge computing and IoT, and how they enable real-time data processing and decision-making at the source.
3. What is ArgoCD?
- Discover ArgoCD, a declarative, GitOps continuous delivery tool for Kubernetes, and its role in deploying applications on edge devices.
4. Deployment Using ArgoCD for Edge Devices
- Step-by-step guide on deploying anomaly detection models on edge devices using ArgoCD.
5. Introduction to Apache Kafka and S3
- Explore Apache Kafka for real-time data streaming and Amazon S3 for scalable storage solutions.
6. Viewing Kafka Messages in the Data Lake
- Learn how to view and analyze Kafka messages stored in a data lake for better insights.
7. What is Prometheus?
- Get to know Prometheus, an open-source monitoring and alerting toolkit, and its application in monitoring edge devices.
8. Monitoring Application Metrics with Prometheus
- Detailed instructions on setting up Prometheus to monitor the performance and health of your anomaly detection system.
9. What is Camel K?
- Introduction to Camel K, a lightweight integration framework built on Apache Camel, designed for Kubernetes.
10. Configuring Camel K Integrations for Data Pipelines
- Learn how to configure Camel K for seamless data pipeline integrations in your anomaly detection workflow.
11. What is a Jupyter Notebook?
- Overview of Jupyter Notebooks, an open-source web application for creating and sharing documents with live code, equations, visualizations, and narrative text.
12. Jupyter Notebooks with Code Examples
- Hands-on examples and code snippets in Jupyter Notebooks to help you implement and test anomaly detection models.
Salesforce Integration for Bonterra Impact Management (fka Social Solutions A...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on integration of Salesforce with Bonterra Impact Management.
Interested in deploying an integration with Salesforce for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Building Production Ready Search Pipelines with Spark and MilvusZilliz
Spark is the widely used ETL tool for processing, indexing and ingesting data to serving stack for search. Milvus is the production-ready open-source vector database. In this talk we will show how to use Spark to process unstructured data to extract vector representations, and push the vectors to Milvus vector database for search serving.
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdfMalak Abu Hammad
Discover how MongoDB Atlas and vector search technology can revolutionize your application's search capabilities. This comprehensive presentation covers:
* What is Vector Search?
* Importance and benefits of vector search
* Practical use cases across various industries
* Step-by-step implementation guide
* Live demos with code snippets
* Enhancing LLM capabilities with vector search
* Best practices and optimization strategies
Perfect for developers, AI enthusiasts, and tech leaders. Learn how to leverage MongoDB Atlas to deliver highly relevant, context-aware search results, transforming your data retrieval process. Stay ahead in tech innovation and maximize the potential of your applications.
#MongoDB #VectorSearch #AI #SemanticSearch #TechInnovation #DataScience #LLM #MachineLearning #SearchTechnology
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Partecipate alla presentazione per immergervi in una storia di interoperabilità, standard e formati aperti, per poi discutere del ruolo importante che i contributori hanno in una comunità open source sostenibile.
BIO: Sostenitrice del software libero e dei formati standard e aperti. È stata un membro attivo dei progetti Fedora e openSUSE e ha co-fondato l'Associazione LibreItalia dove è stata coinvolta in diversi eventi, migrazioni e formazione relativi a LibreOffice. In precedenza ha lavorato a migrazioni e corsi di formazione su LibreOffice per diverse amministrazioni pubbliche e privati. Da gennaio 2020 lavora in SUSE come Software Release Engineer per Uyuni e SUSE Manager e quando non segue la sua passione per i computer e per Geeko coltiva la sua curiosità per l'astronomia (da cui deriva il suo nickname deneb_alpha).
Introduction of Cybersecurity with OSS at Code Europe 2024Hiroshi SHIBATA
I develop the Ruby programming language, RubyGems, and Bundler, which are package managers for Ruby. Today, I will introduce how to enhance the security of your application using open-source software (OSS) examples from Ruby and RubyGems.
The first topic is CVE (Common Vulnerabilities and Exposures). I have published CVEs many times. But what exactly is a CVE? I'll provide a basic understanding of CVEs and explain how to detect and handle vulnerabilities in OSS.
Next, let's discuss package managers. Package managers play a critical role in the OSS ecosystem. I'll explain how to manage library dependencies in your application.
I'll share insights into how the Ruby and RubyGems core team works to keep our ecosystem safe. By the end of this talk, you'll have a better understanding of how to safeguard your code.
AI 101: An Introduction to the Basics and Impact of Artificial IntelligenceIndexBug
Imagine a world where machines not only perform tasks but also learn, adapt, and make decisions. This is the promise of Artificial Intelligence (AI), a technology that's not just enhancing our lives but revolutionizing entire industries.
Lunar skylight polarization signal polluted by urban lighting
1. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, D24106, doi:10.1029/2011JD016698, 2011
Lunar skylight polarization signal polluted by urban lighting
C. C. M. Kyba,1,2 T. Ruhtz,1 J. Fischer,1 and F. Hölker2
Received 8 August 2011; revised 28 September 2011; accepted 18 October 2011; published 17 December 2011.
[1] On clear moonlit nights, a band of highly polarized light stretches across the sky
at a 90 degree angle from the moon, and it was recently demonstrated that nocturnal
organisms are able to navigate based on it. Urban skyglow is believed to be almost
unpolarized, and is therefore expected to dilute this unique partially linearly polarized
signal. We found that urban skyglow has a greater than expected degree of linear
polarization (p = 8.6 Æ 0.3%), and confirmed that its presence diminishes the natural lunar
polarization signal. We also observed that the degree of linear polarization can be reduced
as the moon rises, due to the misalignment between the polarization angles of the skyglow
and scattered moonlight. Under near ideal observing conditions, we found that the lunar
polarization signal was clearly visible (p = 29.2 Æ 0.8%) at a site with minimal light
pollution 28 km from Berlin’s center, but was reduced (p = 11.3 Æ 0.3%) within the
city itself. Daytime measurements indicate that without skyglow p would likely be in
excess of 50%. These results indicate that nocturnal animal navigation systems based on
perceiving polarized scattered moonlight likely fail to operate properly in highly light-
polluted areas, and that future light pollution models must take polarization into account.
Citation: Kyba, C. C. M., T. Ruhtz, J. Fischer, and F. Hölker (2011), Lunar skylight polarization signal polluted by urban
lighting, J. Geophys. Res., 116, D24106, doi:10.1029/2011JD016698.
1. Introduction using polarization cues during twilight [Cochran et al.,
2004; Muheim et al., 2006]. While the lunar polarization
[2] The extreme distance to the Sun and Moon ensures
signal exhibits almost the same degree of linear polarization
that when their light enters Earth’s atmosphere it is highly
and pattern as the solar one [Gál et al., 2001], the intensity
collimated. When this light is scattered by atmospheric
of moonlight is up to seven orders of magnitude lower than
molecules (Rayleigh scattering), the scattered light becomes
sunlight, making its detection far more challenging
linearly polarized, with the degree of linear polarization ( p)
[Warrant, 2004]. Despite this difficulty, it has been shown
depending upon the scattering angle. The value of p is that a species of dung beetle (Coleoptera: Scarabaeinae)
maximal at angles 90° from the source, so on clear days at
navigates using the lunar polarization signal even at the
sunset and sunrise a compass-like band of highly polarized
time of the crescent moon [Dacke et al., 2003, 2011], and
light extends across the sky through the zenith along an
it is suspected that other nocturnal organisms (e.g., moths
approximately North–South axis. Advances in digital
[Nowinszky, 2004; Nowinszky and Puskás, 2011], bees,
imaging have allowed quantitative measurements of this
crickets, and spiders [Warrant and Dacke, 2010; Dacke
pattern during the day [North and Duggin, 1997], twilight
et al., 2011]) make use of this same signal.
[Cronin et al., 2006], and on moonlit nights [Gál et al.,
[4] Although understanding of the extent to which noc-
2001]. Digital imaging has also been used to study light
turnal animals use the lunar polarization signal is in its
pollution [Duriscoe et al., 2007], but although light pollution
infancy, the land area over which it is viewable in pristine
is expected to corrupt the natural pattern of celestial polari- form is relentlessly shrinking due to human activity. Both
zation [Cronin and Marshall, 2011], until now the lunar
the lit area of the Earth and the brightness of urban lighting
polarization signal for urban skies has not been reported.
have increased dramatically over the last century, and it is
[3] It has long been known that many diurnal animals are possible that the navigation systems of moths in brightly lit
able to perceive linearly polarized light [Verkhovskaya,
Europe have been affected through screening of polarized
1940], and exploit the solar polarization signal as a naviga-
moonlight [Nowinszky and Puskás, 2011]. Worldwide,
tional aid [von Frisch, 1949; Horváth and Varjú, 2004].
the annual rate of lighting increase is estimated to be 3-6%,
Songbirds, for example, calibrate their magnetic compass
with large local variations [Narisada and Schreuder, 2004;
Hölker et al., 2010a]. The past two decades have seen
1
increasing recognition of the ecological impacts that both
Institute for Space Sciences, Freie Universität Berlin, Berlin, Germany.
2
Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin,
direct [Rydell, 1992; Salmon et al., 1995] and indirect
Germany. [Moore et al., 2000] night lighting have on organisms, food
webs, and ecosystems [Rich and Longcore, 2006; Navara
Copyright 2011 by the American Geophysical Union. and Nelson, 2007; Hölker et al., 2010b].
0148-0227/11/2011JD016698
D24106 1 of 7
2. D24106 KYBA ET AL.: POLLUTION OF LUNAR SKYLIGHT SIGNAL D24106
Figure 1. Spatial distribution of light pollution. (a) The upward directed radiance measured over Berlin
by the Defense Meteorological Satellite Program in 2006 (image is oriented so that North is upward). The
crosses mark the rural and urban locations we compared on February 21–22, 2011. Comparison of the
brightness of the sky observed at the (b) rural and (c) urban locations. The images are centered on
the North Star, and pixel brightnesses are the measured intensity component of the Stokes matrix (S0),
where a maximum value of 450 was set to preserve contrast. In both images East (toward Berlin’s center)
is in the right hand direction and upwards (downward) is toward the zenith (horizon). Image and data pro-
cessing by NOAA’s National Geophysical Data Center. DMSP data collected by US Air Force Weather
Agency. Outline of Berlin added by Helga Kuechly.
[5] While the light produced by typical street lamps is images of the daylit sky from the urban location, and of a
normally not strongly polarized, light pollution in urban highly polarized LCD screen in the laboratory.
areas can become polarized both through the scattering of [7] The data for the urban–rural comparison were taken on
light by the atmosphere [Kerola, 2006], and through reflec- the night of February 21–22, 2011. To ensure an adequate
tions from natural or artificial planar surfaces [Können, polarization signal, we required a night with extremely clear
1985; Horváth et al., 2009] (e.g., lake water, asphalt, and skies and as full a moon as possible. Perfectly clear skies were
glass windows). The skyglow seen by an urban observer is critical, as clouds strongly amplify urban light pollution
not expected to be highly polarized [Kerola, 2006], because [Kyba et al., 2011; Lolkema et al., 2011] (increasing the
the sources of light are distributed around the observer (i.e., background), and reduce p [Pomozi et al., 2001] (decreasing
the light is uncollimated). An important exception to this the signal). Such optimal observation nights occur only a few
generalization is light scattered from the collimated beam of times per year, so the typical urban polarization signal is
a searchlight, which can be strongly polarized in a clean expected to be considerably smaller than that reported. The
atmosphere [Können, 1985]. When unpolarized light is urban moonlit images were taken from 00:30–00:45, when
added to polarized light, the value of p is decreased. There- the moon was approximately 14 degrees above the horizon,
fore, the brighter a city’s skyglow, the greater we expect the 81.5% illuminated, and the angle between the Moon and
lunar polarization pattern to be polluted. Polaris (the North Star) was 105.5°. The rural images were
taken from 2:02–2:19, when the moon was 21 degrees above
2. Methods the horizon, 80.9% illuminated, and with 105.4° between the
moon and Polaris. For comparison, moonrise images were
2.1. Measurement Locations and Dates taken from 23:06–23:14, and moonless images were taken the
[6] Berlin is an ideal site to perform light pollution following evening, which was also clear, from 22:13–22:40.
research, as the surrounding area in the state of Branden-
burg has comparatively little lighting. This can be seen in 2.2. Image Acquisition
Figure 1a, which shows the view of Berlin from space. We [8] All data were taken using a Finger Lakes Instrument
took data at the two locations marked by the black and (FLI) Microline camera (Kodak KAI-4022 chip, cooled to
white crosses in Figure 1a. The urban location is our À15 C), Sigma 24 mm F1.8 DG lens, and Hama pro class
measurement tower at the Freie Universität (52.4577°N, 77 mm linearly polarizing filter. Night (day) images were
13.3107°E), and the rural location is an unlit parking taken with the aperture set to F2.8 (F22), and with an inte-
lot (52.5296°N, 12.9978°E) adjacent to the “Sielmanns gration time of 5 s (10 ms). Wavelength ranges were
Naturlandschaft Döberitzer Heide” Naturschutzgebiet (wild- restricted using an FLI CFW-1-8 filter wheel with FLI
life sanctuary). Figures 1b and 1c show the sky brightness 28 mm color filters. The approximate wavelength ranges are
at these two locations. As a test of our method, we also took shown later with the results, and detailed transmission curves
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3. D24106 KYBA ET AL.: POLLUTION OF LUNAR SKYLIGHT SIGNAL D24106
are available online (www.flicamera.com/filters/index.html). [12] To ensure the urban–rural comparison was based on
It should be noted that the red filter does not have strong exactly the same patch of the sky, we identified all star-free
transmission at the 589 nm line produced by low pressure pixels within 64 re-binned pixels of Polaris. Stars were
sodium lamps [Elvidge et al., 2010]. This is not expected to removed by flagging all pixels for which the multiimage
have an impact on the interpretation of our results, both variance of S0 was at least three times that for the average
because the light from this line is transmitted by the lumi- pixel. The four intensity values, I0, I45, I90, and I135, are the
nous filter and because Berlin uses an extremely wide range mean value of the remaining star-free pixels.
of lighting technologies. Dark current measurements were [13] For each observation we took 4–6 sets of images, and
taken concurrently with the color images. An opaque filter in all cases we report the polarization measurement from the
was used to block the light for the dark current measure- third set. We refrained from combining the data from mul-
ment, and when the images were analyzed it was discovered tiple acquisitions because the polarization angle of scattered
that this filter blocked only 99.3% of the incoming light. moonlight is not constant, and because Berlin’s skyglow
Measured polarization values were multiplied by 1.014 to becomes dimmer as the night progresses [Kyba et al., 2011].
compensate for this light leakage.
2.4. Estimation of Uncertainties
2.3. Image Processing [14] The two largest sources of uncertainty for p and the
[9] Images were acquired using the Astroart 4 data polarization angle arose from filter mis-alignment and CCD
acquisition program, and analysis was performed using the dark current fluctuations. To estimate the standard error from
Interactive Data Language (IDL). The images were centered these statistical variations, we wrote a Monte Carlo simula-
on the North Star, ensuring that the angle between the moon tion in FORTRAN. For each observed p and polarization
and the center of the image (105.5°) remained the same angle, we simulated 10,000 observations with normally
at each location. Image data were background corrected distributed filter position errors and dark current fluctua-
pixel-by-pixel, and re-binned from 2048 Â 2048 pixels to tions. The standard error was defined as the root mean
256 Â 256 pixels, to improve individual pixel statistics. The square spread of this distribution.
field of view was 33.9° along each axis. [15] This code was used with the daytime measurements
[10] The degree of linear polarization can be obtained with to estimate our 1s filter positioning uncertainty as $1°. The
measurements at three angles of the transmission direction of resulting simulated standard errors agreed well with the
the linear polarizer [Gál et al., 2001; Cronin et al., 2006], statistical variation observed in multiple measurements.
but we made use of a fourth measurements to allow a check (The one exception was for the case of the LCD screen,
of the filter alignment [North and Duggin, 1997]. We define where the assigned uncertainties were larger than the
the Stoke’s vector S as observed variation. We attributed this to the far more com-
0 1 01 1 fortable working conditions in the laboratory, where we
S0 ðI0 þ I45 þ I90 þ I135 Þ C were able to position the filter more accurately.) We found
BS C B2B C that the test statistic dp was non-zero, indicating a systematic
S ¼B 1C¼B
@ S2 A @
I0 À I90 C ð1Þ
I45 À I135 A offset of $2.5° in at least one of the filter positions. We
S3 ≡0 estimate that this results in a systematic deviation of the
degree of linear polarization measurements of Æ3% of
where I45° is the intensity measured with the filter turned to the measured value. This systematic offset should apply
the 45° position. We have assumed that circular polarization approximately equally to all measurements, and is therefore
is absent. The degree of linear polarization is then irrelevant for the urban/rural comparison. It is negligible
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ffi compared to the intrinsic variation due to changes in the
S1 þ S2
2 2 moon’s illuminated fraction and elevation.
p¼ ð2Þ
S0
3. Results
[11] For a perfect measurement, the sum of measurements [16] Figure 1 demonstrates that the intensity of light
taken with polarizations at right angles should be indepen- escaping and reflected by the atmosphere depends upon
dent of the angles. We define a test variable for the filter proximity to urban areas. The degree of linear polarization
alignment: from skyglow and moonlight at the urban and rural sites
d p ¼ ½ðI0 þ I90 Þ À ðI45 þ I135 ÞŠ=S0 ð3Þ are compared to each other and to reference situations in
Table 1. The observed rural degree of linear polarization
which should be zero for perfectly aligned filters (assuming (p = 29.2 Æ 0.8%) was clearly observable, but only about
a stable light field and no CCD noise). Finally, we define an half of what we observed for a sunlit sky (p = 56.6 Æ 1%). In
angle of polarization relative to the filter position at 0°: contrast, the lunar polarization signal was very weak when
observed within the city (p = 11.3 Æ 0.3%). Given that we
S1 performed these measurements in almost ideal conditions
f ¼ 0:5 arccos pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi S2 0 ð4Þ
S1 þ S2
2 2 (cloud free, and with the moon 81% illuminated), it is to be
expected that on most nights the lunar polarization signal is
no longer discernible in many urban locations by the
S1 organisms capable of perceiving it in un-lit environments.
f ¼ p À 0:5 arccos pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi S2 0 ð5Þ
S1 þ S2
2 2 [17] The polarization of urban skyglow in the absence of
the moon (8.6 Æ 0.3%) was larger than we expected, and
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4. D24106 KYBA ET AL.: POLLUTION OF LUNAR SKYLIGHT SIGNAL D24106
Table 1. Degree of Linear Polarization Resultsa
Luminous Red Green Blue
Location Situation (370–700 nm) (590–690 nm) (490–580 nm) (370–510 nm)
Urban No Moon 8.6 Æ 0.3% 8.5 Æ 1.4% 9.4 Æ 0.7% 10.1 Æ 0.5%
Urban Moonrise 3.9 Æ 0.2% - - -
Urban Moon 11.3 Æ 0.3% 8 Æ 2% 12.7 Æ 0.8% 16.7 Æ 1.1%
Rural Moon 29.2 Æ 0.8% 21 Æ 5% 31 Æ 2% 36 Æ 2%
Urban Daytime 56.6 Æ 1.0% 56 Æ 1.1% 57.7 Æ 1.1% 57.2 Æ 1.1%
Laboratory LCD screen 98.1 Æ 1.2% 99.2 Æ 1.2% 98.4 Æ 1.2% 98.3 Æ 1.2%
a
The degree of linear polarization observed for each location and situation is shown, along with 1s statistical standard error.
The reduction in polarization caused by urban light pollution is worse at longer wavelengths, which we presume to be due to
both the stronger scattering of moonlight at short wavelengths, and the comparatively low color temperature of Berlin’s street
lights. An additional systematic uncertainty of $3% of the measured value (due to systematic filter mis-alignment) applies
equally to all measurements. Note that the uncertainty in the measured values is much smaller than the intrinsic variability
caused by gross changes in urban illumination and moon elevation [Kyba et al., 2011]. All night sky data were taken
February 21 and 22, 2011.
considerably larger than the $2% predicted by a recent light reduces the degree of linear polarization, as is shown in
pollution model that takes polarization into account [Kerola, Figure 2a. Provided the moon is bright enough, as it rises the
2006]. We speculate on the possible origin of this polariza- strongly polarized scattered moonlight will begin to domi-
tion in the conclusion, and simply note here that this level of nate over the weakly polarized skyglow, and p will increase,
urban skyglow polarization could have biological implica- as can be seen after 1:30. (The increased spread in the data at
tions for clear moonless nights, as crickets are able to per- this time was probably due to the visually observed passage
ceive the polarization signal of the sky if p exceeds 5% of thin cirrus clouds over the field of view). The dip in p
[Horváth and Varjú, 2004]. shown in Figure 2a and the rotation of the angle of polari-
[18] The weakest polarization values we observed were, zation shown in Figure 2b were most pronounced for blue
somewhat surprisingly, for the case of the rising moon. We light, and least pronounced for red (this is not shown to
believed this to be due to a mismatch between the angle of preserve clarity).
polarization of skyglow and scattered moonlight, and per- [19] Outside of the tropics, the full moon rises to much
formed a dedicated moonrise experiment at the urban loca- lower elevations in summer than in winter. Since the moon
tion on the night of May 21–22, 2011 to test this. We found provides less light at lower elevations, in general we expect
that when the polarization angle of moonlight differs from the washing out of the lunar polarization signal be greatest in
that of skyglow, the introduction of moonlight initially summer, and during moonrise and moonset. We found that
Figure 2. Changes in urban sky polarization during moonrise. (a) The measured degree of linear polar-
ization decreasing immediately after moonrise (dashed line), and gradually increasing again as moonlight
began to dominate over skyglow. (b) The rotation of the angle of polarization as the scattered moonlight is
added. All data are for the luminous filter, with 1s standard errors shown. These data were taken on
May 21–22, 2011, when the moon was not as full or as high in the sky as in the other measurements
(i.e. the transition from skyglow to moonlight dominance was far more rapid on February 21–22). The
onset of sunrise prevented further measurements. The pattern of polarization in pristine moonlit skies is
discussed in detail by Gál et al. [2001].
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5. D24106 KYBA ET AL.: POLLUTION OF LUNAR SKYLIGHT SIGNAL D24106
Figure 3. The dependence of sky brightness and degree of linear polarization on viewing direction.
Shown are data acquired with the luminous filter at the urban location on the night of January 16–17,
2011. (a and c) The sky and horizon brightness (note factor of 10 difference in scale, the darkest sky pixels
in Figure 3c have a value of $550). (b and d) The degree of linear polarization calculated for each pixel
(stars are masked out in Figure 3b). The gradient in Figure 3b arises from changes in the Rayleigh scatter-
ing angle (the moon is far away from the image, in the upward and left direction). The gradient in Figure 3d
is due to unpolarized light pollution blocking the moon’s signal (the moon is even further away in this
image, behind the observer). The sky polarization is larger than in Table 1 because the moon was higher
and fuller.
for the exceptionally high elevation winter moon on the night linear polarization was not comparable to that observed for
of January 16–17, 2011 (52° elevation, 89% illuminated), scattered sunlight at the same urban location (see Table 1).
the scattered moonlight was bright enough to dominate over
the mostly unpolarized urban skyglow. This allowed us to 4. Discussion and Conclusion
observe the gradient of the natural polarization pattern,
shown in Figure 3. Figures 3a and 3c compare the sky [20] This study demonstrates that in Berlin, and presum-
ably urban areas in general, urban skyglow pollutes the lunar
brightness near Polaris and at the horizon, and Figures 3b
skylight polarization signal to such a degree that on most
and 3d show the degree of linear polarization for the same
scenes. The sky gradient in Figure 3b is mainly due to nights polarization-based animal navigation is no longer
expected to be possible. This occurs because skyglow has a
changes in the Rayleigh scattering angle, whereas toward
low value of polarization compared to scattered moonlight,
the horizon (panel D) p decreases due to the increasing
and when unpolarized light is mixed with polarized light the
fraction of (mostly unpolarized) skyglow. Even under these
total degree of linear polarization ( p) is reduced.
extraordinarily favorable observing conditions the degree of
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6. D24106 KYBA ET AL.: POLLUTION OF LUNAR SKYLIGHT SIGNAL D24106
[21] Many nocturnal organisms are believed to orient their study of both the polarization of urban nightscapes and
movements using the polarization of the moonlit sky. nocturnal polarization-based navigation.
Unfortunately, it is very difficult to experimentally verify
this, particularly for the case of flying insects, and further [25] Acknowledgments. This work was supported by the project
Verlust der Nacht (funded by the Federal Ministry of Education and
research into this area is warranted. Since skyglow can Research, Germany, BMBF-033L038A) and by focal area MILIEU (FU
propagate great distances from an urban core, the ecological Berlin). C.K. and T.R. thank their families for understanding their repeated
impact of light pollution may extend over vast swaths of the absence around the time of full moon.
Earths surface, including places where the sky already
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