- The rings of Jupiter show vertical corrugations resembling patterns detected in Saturn's rings, which are caused by the rings being tilted and slowly twisting into spirals due to planetary gravity.
- Galileo images from 1996 and 2000 of Jupiter's rings revealed two spiral pattern wavelengths that are associated with the Shoemaker-Levy 9 comet impacts in 1994 and another event in 1990.
- New Horizons images of the rings in 2007 continued to show the pattern from 1994, demonstrating the longevity of these imprints from comet impacts.
- Saturn's C ring was observed to have a subtle vertical corrugation extending across its entire width, revealed when the rings were illuminated edge-on.
- The corrugation has amplitudes between 2-20 meters and wavelengths of 30-80 km. Radial trends in the wavelength indicate it resulted from differential nodal regression after the ring plane became tilted in 1983.
- The corrugation likely originated from the same event that tilted the ring plane, which is inferred to have been an impact with an extensive cloud of debris rather than a single object, based on the large radial scale of the feature.
The document describes research by the MOA collaboration that detected evidence of free-floating planetary mass objects using gravitational microlensing. They analyzed 1000 microlensing events, identifying 10 with extremely short durations (tE < 2 days) indicating planetary masses. Follow-up analysis by the OGLE collaboration confirmed 7 of these 10 events, providing strong evidence for an unbound or distant population of planetary mass objects.
This document analyzes cosmic phenomena using the Heaviside field, which is an analogy between Maxwell's equations and gravitational theory. Key points:
1) The Maxwell analogue equations and Lorentz force law can explain the formation of disc galaxies from angular collapse of orbits into a galaxy's equatorial plane, as well as the constant velocity of stars in disc galaxies.
2) These laws also describe phenomena like the dynamics of fast-spinning stars and supernova remnants, binary pulsars and accretion discs, and polar bursts from matter falling toward pulsars' poles.
3) The equations allow calculating metrics like the critical compression radius below which fast-spinning stars maintain a global compression regardless of rotation speed.
De mees-gravitomagnetism-and-coriolis-gravity-2011-a4John Hutchison
This document provides an introduction and table of contents to a book titled "Gravito-magnetism including an introduction to the Coriolis Gravity Theory" by Thierry De Mees. The book aims to explain various phenomena in astrophysics using a novel theory of gravito-magnetism and Coriolis gravity. It covers topics like the formation of planetary systems, galaxies, black holes, and more. The introduction outlines several questions about astrophysical phenomena that existing theories cannot fully explain and presents the author's theory as a simpler alternative approach.
1) Massive black hole binaries form during galaxy mergers and evolve through dynamical friction and 3-body interactions with stars until reaching separations of ~0.01 pc where gravitational wave emission takes over.
2) Gas dynamics may also drive black hole binaries to smaller separations for coalescence.
3) Black hole binary coalescence timescales are typically long, on the order of billions of years, which has implications for gravitational wave detection and triple black hole interactions.
To move into a higher velocity orbit, you need to fire the satellite's thrusters forwards. Firing forwards does negative work, which decreases the potential energy and increases the kinetic energy, resulting in a higher orbital velocity.
This document discusses gravitomagnetism and how it can explain various cosmic phenomena without relying on other assumptions or theories like general relativity. It defines gravitomagnetism and shows how it is analogous to electromagnetism. It then explains how gravitomagnetism can account for: 1) the bending of light near massive objects and Mercury's orbit, 2) the swiveling of inclined orbits toward the equatorial plane of massive objects, and 3) the orbital velocities of objects around spinning stars. It proposes gravitomagnetism can explain other phenomena like supernova shapes, galaxy formation, and the fly-by anomaly. Finally, it discusses an emerging theory of "Coriolis gravity" which links gravit
This paper analyzes photographic observations of the 1995 Quadrantid meteor shower made by the Dutch Meteor Society. The orbits of 95 Quadrantid meteors were precisely measured from photographic plates, providing the highest accuracy orbital data yet for this stream. Analysis of the orbits shows that the dispersion is much less than previous studies, indicating that the main component of the Quadrantid stream is only about 500 years old, much younger than the 5000-7500 years assumed previously. This suggests that the main peak arises from a recent "outburst" rather than the classical dust component. The stream likely does not originate from comet 96P/Machholz 1 as thought, and its true parent body may be an asteroid-like object in a
- Saturn's C ring was observed to have a subtle vertical corrugation extending across its entire width, revealed when the rings were illuminated edge-on.
- The corrugation has amplitudes between 2-20 meters and wavelengths of 30-80 km. Radial trends in the wavelength indicate it resulted from differential nodal regression after the ring plane became tilted in 1983.
- The corrugation likely originated from the same event that tilted the ring plane, which is inferred to have been an impact with an extensive cloud of debris rather than a single object, based on the large radial scale of the feature.
The document describes research by the MOA collaboration that detected evidence of free-floating planetary mass objects using gravitational microlensing. They analyzed 1000 microlensing events, identifying 10 with extremely short durations (tE < 2 days) indicating planetary masses. Follow-up analysis by the OGLE collaboration confirmed 7 of these 10 events, providing strong evidence for an unbound or distant population of planetary mass objects.
This document analyzes cosmic phenomena using the Heaviside field, which is an analogy between Maxwell's equations and gravitational theory. Key points:
1) The Maxwell analogue equations and Lorentz force law can explain the formation of disc galaxies from angular collapse of orbits into a galaxy's equatorial plane, as well as the constant velocity of stars in disc galaxies.
2) These laws also describe phenomena like the dynamics of fast-spinning stars and supernova remnants, binary pulsars and accretion discs, and polar bursts from matter falling toward pulsars' poles.
3) The equations allow calculating metrics like the critical compression radius below which fast-spinning stars maintain a global compression regardless of rotation speed.
De mees-gravitomagnetism-and-coriolis-gravity-2011-a4John Hutchison
This document provides an introduction and table of contents to a book titled "Gravito-magnetism including an introduction to the Coriolis Gravity Theory" by Thierry De Mees. The book aims to explain various phenomena in astrophysics using a novel theory of gravito-magnetism and Coriolis gravity. It covers topics like the formation of planetary systems, galaxies, black holes, and more. The introduction outlines several questions about astrophysical phenomena that existing theories cannot fully explain and presents the author's theory as a simpler alternative approach.
1) Massive black hole binaries form during galaxy mergers and evolve through dynamical friction and 3-body interactions with stars until reaching separations of ~0.01 pc where gravitational wave emission takes over.
2) Gas dynamics may also drive black hole binaries to smaller separations for coalescence.
3) Black hole binary coalescence timescales are typically long, on the order of billions of years, which has implications for gravitational wave detection and triple black hole interactions.
To move into a higher velocity orbit, you need to fire the satellite's thrusters forwards. Firing forwards does negative work, which decreases the potential energy and increases the kinetic energy, resulting in a higher orbital velocity.
This document discusses gravitomagnetism and how it can explain various cosmic phenomena without relying on other assumptions or theories like general relativity. It defines gravitomagnetism and shows how it is analogous to electromagnetism. It then explains how gravitomagnetism can account for: 1) the bending of light near massive objects and Mercury's orbit, 2) the swiveling of inclined orbits toward the equatorial plane of massive objects, and 3) the orbital velocities of objects around spinning stars. It proposes gravitomagnetism can explain other phenomena like supernova shapes, galaxy formation, and the fly-by anomaly. Finally, it discusses an emerging theory of "Coriolis gravity" which links gravit
This paper analyzes photographic observations of the 1995 Quadrantid meteor shower made by the Dutch Meteor Society. The orbits of 95 Quadrantid meteors were precisely measured from photographic plates, providing the highest accuracy orbital data yet for this stream. Analysis of the orbits shows that the dispersion is much less than previous studies, indicating that the main component of the Quadrantid stream is only about 500 years old, much younger than the 5000-7500 years assumed previously. This suggests that the main peak arises from a recent "outburst" rather than the classical dust component. The stream likely does not originate from comet 96P/Machholz 1 as thought, and its true parent body may be an asteroid-like object in a
1) Pulsar timing arrays are searching for gravitational waves from massive black hole binaries in the nanohertz frequency range.
2) Current pulsar timing array efforts have not detected a gravitational wave signal but are placing increasingly stringent upper limits.
3) Future and more sensitive radio telescopes like FAST, MeerKAT, and the Square Kilometre Array will improve the prospects for a direct detection of gravitational waves from massive black hole binaries within the next decade.
The document discusses gravitational waves and binary systems. It provides context on the history of gravitational wave detection, from Einstein's early work developing the theory of gravitational waves to Joseph Weber's pioneering efforts to detect them in the 1960s. It also summarizes the development of laser interferometer gravitational wave detectors by researchers in the US, Germany, Italy, and the UK beginning in the 1970s and 1980s. Key detections by LIGO and Virgo are noted, including GW150914 in 2015. Theoretical work on modeling gravitational waveforms from coalescing compact binaries is summarized, from early perturbative approaches to more recent analytical methods like the effective one-body formalism.
1) The document discusses multi-messenger astronomy and the detection of electromagnetic counterparts to gravitational waves, neutrinos, and cosmic rays.
2) It provides background on neutrino astronomy, gravitational wave detections from binary neutron star mergers, and kilonova emissions from such mergers.
3) The merger of GW170817 and its association with GRB170817A and kilonova AT2017gfo provided the first direct evidence that neutron star mergers are the origin of short gamma-ray bursts and produce r-process nucleosynthesis.
1. The document discusses potential low frequency gravitational wave sources that could be detected by LISA, including galactic white dwarf binaries, massive black hole binaries, and extreme mass ratio inspirals.
2. LISA could detect thousands of massive black hole binaries and provide precise measurements of their parameters like mass and spin, enabling tests of general relativity and learning about black hole formation mechanisms.
3. Extreme mass ratio inspirals where a compact object spirals into a massive black hole could occur at a rate of 10-7 per year in our galaxy, allowing precision cosmology and tests of the no-hair theorem.
This document discusses gravity and Newton's law of universal gravitation. It begins with a brief introduction on historical explanations for why objects stay on Earth and how moons orbit planets. It then explains that Newton correctly identified gravity as the cause of these phenomena. The document goes on to define Newton's law of universal gravitation, which states that the gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. It also provides examples of how gravity explains orbits, tides, and more.
Alessandra Buonanno gave a lecture on the analytical and numerical relativity approaches used to model gravitational waveforms from inspiraling binary systems. She discussed how post-Newtonian theory, effective one body theory, and numerical relativity are used to approximately and exactly solve Einstein's field equations. She emphasized the crucial synergy between analytical and numerical relativity approaches to develop accurate gravitational waveform models like EOBNR and Phenom that have been used to infer astrophysics from LIGO/Virgo detections.
Detection Of Dark Matter (via Gravitational Lensing)
This document discusses how gravitational lensing can be used to detect and measure the mass distribution of dark matter. It explains that dark matter does not emit light but will bend light passing nearby via its gravitational field based on general relativity. Precise measurements of the bending angle using the lens equation can reveal the Einstein angle and corresponding dark matter mass distribution. Microlensing observations of stars in nearby galaxies magnified by potential dark matter candidates like MACHOs moving in galactic halos can reveal characteristic light curves used to detect dark matter presence and estimate its mass.
This document summarizes a lecture on using gravitational wave waveform models to test general relativity and probe the nature of compact objects through gravitational wave observations. It discusses how waveform models can be used to bound post-Newtonian coefficients, constrain phenomenological merger-ringdown parameters, and probe the quasi-normal modes of black hole ringdowns. Measuring multiple modes could verify the no-hair theorem and black hole uniqueness properties. Future observations from LIGO and Virgo at design sensitivity may allow high-precision black hole spectroscopy and tests of general relativity in the strong, dynamical gravity regime.
This document provides information about constants and laws related to gravitational fields that commonly appear on exams for the PAU (University Access Test) in Castilla y León, Spain. It includes the values of gravitational acceleration on Earth (g0), Earth's radius (RT), Earth's mass (MT), and the gravitational constant (G). It then provides example problems applying Kepler's laws and Newton's law of universal gravitation to calculate orbital properties of planets, moons, and satellites. Sample problems calculate orbital periods, velocities, distances, and gravitational accelerations for bodies in the solar system like Jupiter, Mars, Mercury, the Moon, and artificial satellites.
To move a satellite into a higher velocity orbit, you need to fire its thrusters forwards. This decreases the orbital radius, which increases the orbital velocity according to Kepler's third law. Firing backwards would increase the orbital radius and decrease the orbital velocity, putting it into a lower velocity orbit.
General Relativity and gravitational waves: a primerJoseph Fernandez
A short introduction to the one of the nicest bits of physical reasoning ever, which led to Albert Einstein's General Relativity, gravitational waves and our research on gravitational wave sources.
Designed by Joseph John Fernandez for LJMU FET Research Week.
1) The document summarizes the 100-year history of gravitational wave detection, from Einstein's theory of general relativity predicting their existence to the recent direct detection by the LIGO experiment.
2) It describes how LIGO uses laser interferometry to extremely sensitively measure tiny distortions in spacetime caused by passing gravitational waves.
3) The first detected gravitational waves in 2015 matched predictions for the inspiral and merger of two black holes, with the signal analyzed to determine properties of the black holes such as their masses.
The document discusses using gravitational wave waveform models to infer astrophysical properties from observations of gravitational wave events. It describes how waveform models encode information about binary black hole parameters like mass and spin, and how Bayesian inference can be used to estimate these parameters from the detected gravitational wave signal. It also addresses assessing confidence in detections and evaluating potential modeling systematics by comparing waveform models to numerical relativity simulations.
This document summarizes a study that investigated shear-wave attenuation and site response in Guerrero, Mexico using spectra from moderate earthquakes. The researchers developed a method to model spectra assuming an ω-2 source shape and exponential decay to describe attenuation. They were able to separate the spectral decay parameter into distance-dependent and site-dependent components. Comparing observed and model event spectra allowed them to estimate site response effects for different stations, independent of source and path effects. The study found weaker distance dependence of attenuation in Guerrero compared to southern California, but greater near-site attenuation. Significant amplification and deamplification was observed in site response functions for hard rock sites, with no clear correlation with local geology or topography.
Alignment of quasar_polarizations_with_large_scale_structuresSérgio Sacani
This document summarizes research measuring the optical polarization of quasars belonging to large-scale quasar groups at redshift z~1.3. Of 93 quasars observed, 19 were significantly polarized. The polarization vectors of these quasars were found to be either parallel or perpendicular to the directions of the large-scale structures they belong to, with a statistical probability of this being due to random orientations of only ~1%. Quasars with polarization perpendicular to their structures tended to have broader emission lines, while those parallel had narrower lines, suggesting quasar spin axes are parallel to their host large-scale structures.
A closely packed system of low mass, low-density planets transiting kepler-11Sérgio Sacani
The document summarizes the discovery of six transiting exoplanets orbiting the star Kepler-11. Photometry from the Kepler spacecraft revealed periodic dips in the star's brightness consistent with multiple transiting planets. Six planetary candidates were identified, with orbital periods ranging from 10 to 47 days for the inner five planets. Radial velocity measurements confirmed the planetary nature of the five inner planets and allowed for mass estimates. The outermost sixth planet was also validated as a planet. Analysis of the transit times, durations and depths provided insights into the properties, dynamics, and stability of this unique six-planet system.
Polarized gamma ray emission from the galactic black hole cygnus x-1Sérgio Sacani
Polarized gamma-ray emission was measured from the black hole binary system Cygnus X-1 using the INTEGRAL/IBIS telescope. Spectral modeling revealed two emission components: 250-400 keV emission consistent with Compton scattering and weakly polarized; 400 keV - 2 MeV emission from a power law component that is strongly polarized at 67%, likely from synchrotron emission in the jet. The polarization angle of 140° is significantly different than the radio jet angle, as seen in other jet sources.
A mechanism for the present day creation of a new class of black holesSérgio Sacani
This document proposes a mechanism for the formation of new classes of black holes with masses less than 2 solar masses (substellar mass dwarf black holes or DBHs) in the expanding gases of astrophysical phenomena like supernovae. It presents a heuristic method for determining gravitational instability and collapse in non-spherical matter distributions, which could allow detection of regions in simulation data that form DBHs. Applying this method to a Type II supernova simulation, the authors found regions with densities and masses close to what is needed to form DBHs. Future work will estimate the mass spectrum and abundances of ejected and bound DBHs.
Supermassive black holes do not correlate with galaxy disks or pseudobulgesSérgio Sacani
The document summarizes research finding that supermassive black holes do not correlate with galaxy disks or pseudobulges. It finds that black hole mass correlates strongly with classical bulges, which are indistinguishable from elliptical galaxies, but correlates little or not at all with pseudobulges or disks. This suggests two different modes of black hole feeding - rapid growth driven by mergers for classical bulges, and slower local growth for pseudobulges and disks.
Titan is a moon of Saturn with a dense nitrogen-methane atmosphere that allows for organic chemistry on its surface. The Cassini mission and Huygens probe provided data about Titan's surface, which appears to have liquid methane and ethane at some point in its history. Evidence suggests Titan has an internal liquid water layer that allows geological activity like cryovolcanism, and that ammonia plays a key role in maintaining this layer and Titan's evolution.
Search for microscopic black hole signatures at the large hadron colliderSérgio Sacani
The CMS Collaboration at the LHC searched for microscopic black hole signatures using 35 pb-1 of 7 TeV proton-proton collision data. No significant excess beyond standard model expectations was observed in events with high total transverse energy. Limits are set on the minimum black hole mass in the range of 3.5-4.5 TeV for various parameters in the large extra dimensions model. These are the first direct limits on black hole production at a particle collider.
The document summarizes the first observations of the magnetic Kelvin-Helmholtz instability in the solar corona using high-resolution imaging from NASA's Solar Dynamics Observatory. The instability was detected on the northern flank of a fast coronal mass ejection, appearing as substructures or waves against the darker coronal background. Analysis found the observed phase speed of the waves to be about half the speed of the ejecta front, validating theories of the non-linear dynamics of this instability in magnetized plasma environments. The findings provide new insights into fundamental plasma processes in the solar atmosphere and solar-terrestrial system.
1) Pulsar timing arrays are searching for gravitational waves from massive black hole binaries in the nanohertz frequency range.
2) Current pulsar timing array efforts have not detected a gravitational wave signal but are placing increasingly stringent upper limits.
3) Future and more sensitive radio telescopes like FAST, MeerKAT, and the Square Kilometre Array will improve the prospects for a direct detection of gravitational waves from massive black hole binaries within the next decade.
The document discusses gravitational waves and binary systems. It provides context on the history of gravitational wave detection, from Einstein's early work developing the theory of gravitational waves to Joseph Weber's pioneering efforts to detect them in the 1960s. It also summarizes the development of laser interferometer gravitational wave detectors by researchers in the US, Germany, Italy, and the UK beginning in the 1970s and 1980s. Key detections by LIGO and Virgo are noted, including GW150914 in 2015. Theoretical work on modeling gravitational waveforms from coalescing compact binaries is summarized, from early perturbative approaches to more recent analytical methods like the effective one-body formalism.
1) The document discusses multi-messenger astronomy and the detection of electromagnetic counterparts to gravitational waves, neutrinos, and cosmic rays.
2) It provides background on neutrino astronomy, gravitational wave detections from binary neutron star mergers, and kilonova emissions from such mergers.
3) The merger of GW170817 and its association with GRB170817A and kilonova AT2017gfo provided the first direct evidence that neutron star mergers are the origin of short gamma-ray bursts and produce r-process nucleosynthesis.
1. The document discusses potential low frequency gravitational wave sources that could be detected by LISA, including galactic white dwarf binaries, massive black hole binaries, and extreme mass ratio inspirals.
2. LISA could detect thousands of massive black hole binaries and provide precise measurements of their parameters like mass and spin, enabling tests of general relativity and learning about black hole formation mechanisms.
3. Extreme mass ratio inspirals where a compact object spirals into a massive black hole could occur at a rate of 10-7 per year in our galaxy, allowing precision cosmology and tests of the no-hair theorem.
This document discusses gravity and Newton's law of universal gravitation. It begins with a brief introduction on historical explanations for why objects stay on Earth and how moons orbit planets. It then explains that Newton correctly identified gravity as the cause of these phenomena. The document goes on to define Newton's law of universal gravitation, which states that the gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. It also provides examples of how gravity explains orbits, tides, and more.
Alessandra Buonanno gave a lecture on the analytical and numerical relativity approaches used to model gravitational waveforms from inspiraling binary systems. She discussed how post-Newtonian theory, effective one body theory, and numerical relativity are used to approximately and exactly solve Einstein's field equations. She emphasized the crucial synergy between analytical and numerical relativity approaches to develop accurate gravitational waveform models like EOBNR and Phenom that have been used to infer astrophysics from LIGO/Virgo detections.
Detection Of Dark Matter (via Gravitational Lensing)
This document discusses how gravitational lensing can be used to detect and measure the mass distribution of dark matter. It explains that dark matter does not emit light but will bend light passing nearby via its gravitational field based on general relativity. Precise measurements of the bending angle using the lens equation can reveal the Einstein angle and corresponding dark matter mass distribution. Microlensing observations of stars in nearby galaxies magnified by potential dark matter candidates like MACHOs moving in galactic halos can reveal characteristic light curves used to detect dark matter presence and estimate its mass.
This document summarizes a lecture on using gravitational wave waveform models to test general relativity and probe the nature of compact objects through gravitational wave observations. It discusses how waveform models can be used to bound post-Newtonian coefficients, constrain phenomenological merger-ringdown parameters, and probe the quasi-normal modes of black hole ringdowns. Measuring multiple modes could verify the no-hair theorem and black hole uniqueness properties. Future observations from LIGO and Virgo at design sensitivity may allow high-precision black hole spectroscopy and tests of general relativity in the strong, dynamical gravity regime.
This document provides information about constants and laws related to gravitational fields that commonly appear on exams for the PAU (University Access Test) in Castilla y León, Spain. It includes the values of gravitational acceleration on Earth (g0), Earth's radius (RT), Earth's mass (MT), and the gravitational constant (G). It then provides example problems applying Kepler's laws and Newton's law of universal gravitation to calculate orbital properties of planets, moons, and satellites. Sample problems calculate orbital periods, velocities, distances, and gravitational accelerations for bodies in the solar system like Jupiter, Mars, Mercury, the Moon, and artificial satellites.
To move a satellite into a higher velocity orbit, you need to fire its thrusters forwards. This decreases the orbital radius, which increases the orbital velocity according to Kepler's third law. Firing backwards would increase the orbital radius and decrease the orbital velocity, putting it into a lower velocity orbit.
General Relativity and gravitational waves: a primerJoseph Fernandez
A short introduction to the one of the nicest bits of physical reasoning ever, which led to Albert Einstein's General Relativity, gravitational waves and our research on gravitational wave sources.
Designed by Joseph John Fernandez for LJMU FET Research Week.
1) The document summarizes the 100-year history of gravitational wave detection, from Einstein's theory of general relativity predicting their existence to the recent direct detection by the LIGO experiment.
2) It describes how LIGO uses laser interferometry to extremely sensitively measure tiny distortions in spacetime caused by passing gravitational waves.
3) The first detected gravitational waves in 2015 matched predictions for the inspiral and merger of two black holes, with the signal analyzed to determine properties of the black holes such as their masses.
The document discusses using gravitational wave waveform models to infer astrophysical properties from observations of gravitational wave events. It describes how waveform models encode information about binary black hole parameters like mass and spin, and how Bayesian inference can be used to estimate these parameters from the detected gravitational wave signal. It also addresses assessing confidence in detections and evaluating potential modeling systematics by comparing waveform models to numerical relativity simulations.
This document summarizes a study that investigated shear-wave attenuation and site response in Guerrero, Mexico using spectra from moderate earthquakes. The researchers developed a method to model spectra assuming an ω-2 source shape and exponential decay to describe attenuation. They were able to separate the spectral decay parameter into distance-dependent and site-dependent components. Comparing observed and model event spectra allowed them to estimate site response effects for different stations, independent of source and path effects. The study found weaker distance dependence of attenuation in Guerrero compared to southern California, but greater near-site attenuation. Significant amplification and deamplification was observed in site response functions for hard rock sites, with no clear correlation with local geology or topography.
Alignment of quasar_polarizations_with_large_scale_structuresSérgio Sacani
This document summarizes research measuring the optical polarization of quasars belonging to large-scale quasar groups at redshift z~1.3. Of 93 quasars observed, 19 were significantly polarized. The polarization vectors of these quasars were found to be either parallel or perpendicular to the directions of the large-scale structures they belong to, with a statistical probability of this being due to random orientations of only ~1%. Quasars with polarization perpendicular to their structures tended to have broader emission lines, while those parallel had narrower lines, suggesting quasar spin axes are parallel to their host large-scale structures.
A closely packed system of low mass, low-density planets transiting kepler-11Sérgio Sacani
The document summarizes the discovery of six transiting exoplanets orbiting the star Kepler-11. Photometry from the Kepler spacecraft revealed periodic dips in the star's brightness consistent with multiple transiting planets. Six planetary candidates were identified, with orbital periods ranging from 10 to 47 days for the inner five planets. Radial velocity measurements confirmed the planetary nature of the five inner planets and allowed for mass estimates. The outermost sixth planet was also validated as a planet. Analysis of the transit times, durations and depths provided insights into the properties, dynamics, and stability of this unique six-planet system.
Polarized gamma ray emission from the galactic black hole cygnus x-1Sérgio Sacani
Polarized gamma-ray emission was measured from the black hole binary system Cygnus X-1 using the INTEGRAL/IBIS telescope. Spectral modeling revealed two emission components: 250-400 keV emission consistent with Compton scattering and weakly polarized; 400 keV - 2 MeV emission from a power law component that is strongly polarized at 67%, likely from synchrotron emission in the jet. The polarization angle of 140° is significantly different than the radio jet angle, as seen in other jet sources.
A mechanism for the present day creation of a new class of black holesSérgio Sacani
This document proposes a mechanism for the formation of new classes of black holes with masses less than 2 solar masses (substellar mass dwarf black holes or DBHs) in the expanding gases of astrophysical phenomena like supernovae. It presents a heuristic method for determining gravitational instability and collapse in non-spherical matter distributions, which could allow detection of regions in simulation data that form DBHs. Applying this method to a Type II supernova simulation, the authors found regions with densities and masses close to what is needed to form DBHs. Future work will estimate the mass spectrum and abundances of ejected and bound DBHs.
Supermassive black holes do not correlate with galaxy disks or pseudobulgesSérgio Sacani
The document summarizes research finding that supermassive black holes do not correlate with galaxy disks or pseudobulges. It finds that black hole mass correlates strongly with classical bulges, which are indistinguishable from elliptical galaxies, but correlates little or not at all with pseudobulges or disks. This suggests two different modes of black hole feeding - rapid growth driven by mergers for classical bulges, and slower local growth for pseudobulges and disks.
Titan is a moon of Saturn with a dense nitrogen-methane atmosphere that allows for organic chemistry on its surface. The Cassini mission and Huygens probe provided data about Titan's surface, which appears to have liquid methane and ethane at some point in its history. Evidence suggests Titan has an internal liquid water layer that allows geological activity like cryovolcanism, and that ammonia plays a key role in maintaining this layer and Titan's evolution.
Search for microscopic black hole signatures at the large hadron colliderSérgio Sacani
The CMS Collaboration at the LHC searched for microscopic black hole signatures using 35 pb-1 of 7 TeV proton-proton collision data. No significant excess beyond standard model expectations was observed in events with high total transverse energy. Limits are set on the minimum black hole mass in the range of 3.5-4.5 TeV for various parameters in the large extra dimensions model. These are the first direct limits on black hole production at a particle collider.
The document summarizes the first observations of the magnetic Kelvin-Helmholtz instability in the solar corona using high-resolution imaging from NASA's Solar Dynamics Observatory. The instability was detected on the northern flank of a fast coronal mass ejection, appearing as substructures or waves against the darker coronal background. Analysis found the observed phase speed of the waves to be about half the speed of the ejecta front, validating theories of the non-linear dynamics of this instability in magnetized plasma environments. The findings provide new insights into fundamental plasma processes in the solar atmosphere and solar-terrestrial system.
A massive protocluster of galaxies at a redshift of z<5.3Sérgio Sacani
This document describes the discovery of a massive protocluster of galaxies located approximately 1 billion years after the Big Bang (redshift of z=5.3). The protocluster contains overdense regions of massive galaxies extending over 13 megaparsecs. It contains an extremely luminous starburst galaxy with large molecular gas reserves and a luminous quasar. Together, these objects place a minimum total mass of over 4×1011 solar masses in this early cluster, consistent with cosmological simulations of the earliest galaxy clusters. This discovery provides evidence for the hierarchical formation of massive structures in the early universe.
Zero outward flow velocity for plasma in a heliosheath transition layeSérgio Sacani
The document summarizes recent findings from Voyager 1, which has been traveling through the heliosheath region between the solar wind termination shock and the heliopause boundary. Key findings include:
1) The radial velocity of plasma detected by Voyager 1 has decreased nearly linearly from 70 km/s to 0 km/s over the past 3 years and has remained at 0 km/s for the past 8 months, indicating Voyager 1 has entered a transition layer with zero radial flow.
2) This transition layer was not predicted by models and contradicts expectations of an abrupt discontinuity at the heliopause.
3) Analysis of plasma velocity measurements suggests Voyager 1 may have crossed the he
The high albedo of the hot jupiter kepler 7 bSérgio Sacani
This document summarizes the analysis of Kepler photometry data for the exoplanet Kepler-7b. Key findings include:
1) The occultation depth is measured to be 44±5 ppm, translating to a Kepler geometric albedo of 0.32±0.03, the most precise value measured for an exoplanet.
2) The planetary orbital phase lightcurve is characterized with an amplitude of 42±4 ppm.
3) Atmospheric modeling finds it unlikely that the high albedo is due to a dominant thermal component. Two possible explanations are proposed: excess reflection from clouds/hazes, or depleted atmospheric sodium and potassium allowing Rayleigh scattering to dominate.
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.
MUSE sneaks a peek at extreme ram-pressure stripping events. I. A kinematic s...Sérgio Sacani
- MUSE observations of the galaxy ESO137-001 reveal an extended gaseous tail over 30 kpc long traced by H-alpha emission, providing evidence of an extreme ram pressure stripping event as the galaxy falls into the massive Norma galaxy cluster.
- Analysis of the H-alpha kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center, with gravitational interactions not appearing to be the main mechanism of gas removal.
- The stripped gas retains evidence of the disk's rotational velocity out to around 20 kpc downstream, indicating the galaxy is moving radially along the plane of the sky, while
Brazil has a long history in astronomy dating back to the 17th century when the first astronomical observatory was founded in Recife. Astronomy grew slowly over the centuries and accelerated in recent decades due to new funding, graduate programs, and infrastructure like the OPD telescope. Brazil now participates in international observatories like Gemini, SOAR, and CFHT to give its astronomers access to a wide range of telescopes. The national astronomical community has grown rapidly to over 650 scientists spread across 46 institutions nationwide. Brazil also develops astronomical instrumentation through organizations like LNA and INPE.
1. VFTS 682 is a very massive star located 29 pc in projection from the young massive cluster R136 in the Tarantula Nebula of the LMC.
2. Spectral modeling finds it has an unusually high luminosity of log(L/L) = 6.5, corresponding to a present-day mass of ~150 solar masses.
3. Its isolation and mass pose the question of whether it formed in situ, which would profoundly impact theories of massive star formation, or if it was ejected from R136, making it the most massive runaway star known.
Counterjet infrared symmetry of hh 34 and the size of the jet formation regionSérgio Sacani
The document summarizes new Spitzer IRAC images of the HH 34 outflow that detect both the southern jet and northern counterjet with comparable intensities and surprising symmetry. This removes the problem of apparent asymmetry close to the source versus large-scale symmetry. Quantitative analysis shows the counterjet knots are positioned symmetrically to within 0.11-1.57 pixels of the corresponding jet knots. This degree of symmetry implies the jet production region has a characteristic size less than 2.8 AU, providing the strongest constraint yet on the size of the region producing HH jets.
Pesquisa mostra que as exoluas podem ser os corpos mais comuns no universo onde se pode encontrar vida. As exoluar aumentam o número de corpos presentes na chamada zona habitável dos exoplanetas.
This document describes the Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES) catalog, which contains 1342 very wide (projected separation >500 AU), low-mass (at least one mid-K to mid-M dwarf component) common proper motion pairs identified from the Sloan Digital Sky Survey. The catalog was constructed using astrometry, photometry, and proper motions to identify pairs with a probability of chance alignment ≤0.05. The catalog is intended to be a resource for detailed study of low-mass binary star systems and preliminary results describe the properties and characteristics of the wide, low-mass pairs.
Artigo relata como a Terra sofreu com os impactos de ateroides a 4 bilhões de anos atrás, e como a superfície do planeta foi remodelada e os oceanos formados.
X raying the ejecta of supernova 1987 aSérgio Sacani
This study analyzed observations of Supernova 1987A (SN 1987A) from 1994 to 2009 using the Hubble Space Telescope. [1] From 1994 to 2001, the brightness of the ejecta faded as expected due to radioactive decay. [2] After 2001, the brightness began increasing, reaching over twice the 2001 level by 2009. [3] This study finds that the increase is caused by X-rays from the collision between the ejecta and surrounding circumstellar ring, which deposits heat in the ejecta and powers its increased brightness.
Detection of visible light from the darkest worldSérgio Sacani
This document reports the detection of visible light from the exoplanet TrES-2b using Kepler photometry data. The analysis finds a day-night contrast amplitude of 6.5 ± 1.9 parts per million, representing the lowest amplitude orbital phase variation discovered. This signal is detected at a confidence level of 99.98% and persists across different models of the data, appearing robust. If interpreted as scattering, it corresponds to a geometric albedo of 0.0253±0.0072 for TrES-2b, making it the darkest exoplanet detected so far. However, models indicate significant day-side emission, implying an even lower true albedo.
This document summarizes a paper that presents models for locations and motions in the solar system. Ratios of orbital angular velocities are shown for planets and moons, with common ratios around 2.5 that may relate to an L-frequency. A generalized elliptic orbit model is derived, giving angular velocity as a function of eccentricity and L-frequency. Frequency ratios found in musical instruments and the northern lights are also discussed. Preliminary models for fractal locations using an iteration formula producing a Julia set are presented.
Artigo descreve a descoberta feita pelo Hubble de que duas luas de Plutão descrevem suas órbitas realizando cambalhotas imprevisíveis. Além disso, o estudo descobriu um link entre as órbitas das luas menores de Plutão.
Photometry of Giant Propellers in Saturn's RingsJakaylaRobinson
1) The document discusses analyzing images of "giant propellers" in Saturn's rings taken by Cassini during its Ring Grazing Orbit and Grand Finale.
2) The authors use images of the propeller "Santos-Dumont" taken on the lit and unlit sides to investigate how the propeller's brightness relates to its optical depth, by comparing predicted and observed brightness values.
3) They find the brightness ratio between prediction and observation is consistent in translucent parts of the propeller and ring, but varies more in opaque parts, helping evaluate differences between empty and opaque regions.
Discovery of powerful gamma ray flares from the crab nebulaSérgio Sacani
1) The AGILE satellite detected powerful gamma-ray flares from the Crab Nebula in September 2010 and October 2007 that increased the nebula's unpulsed gamma-ray flux by a factor of 3.
2) The flares originated near the nebula's central pulsar and challenge standard models of nebular emission.
3) Synchrotron emission from shock-accelerated electrons along the pulsar's polar jet can explain the gamma-ray flaring, requiring particle acceleration on timescales of about 1 day.
1) High-dispersion spectroscopy was used to observe the young exoplanet Beta Pictoris b, detecting a blueshifted radial velocity of -15±1.7 km/s and rotational broadening of 25±3 km/s, indicating it spins faster than any planet in the solar system.
2) Beta Pictoris b's high spin velocity is consistent with an extrapolation of the trend of increasing spin velocity with planet mass seen in the solar system.
3) At an estimated age of 11±5 Myr, Beta Pictoris b is expected to cool and shrink over time, which would cause it to spin up further to a rotation velocity of around 40 km/s.
1) The gamma-ray burst GRB 101225A is explained as being caused by the tidal disruption of a minor body (such as an asteroid or comet) falling onto an isolated neutron star.
2) The light curves and spectra observed across multiple wavelengths are consistent with the predictions of the tidal disruption model.
3) A minor body passing within 105-106 km of a neutron star would be disrupted by the star's tidal forces, with the debris falling back to form an accretion disk around the star and emitting radiation.
This paper considers the plausibility of time dilation effects shown in the film Interstellar. It calculates that for an hour to pass on a planet orbiting a 100 million solar mass black hole while 7 years pass on Earth, the planet would need to orbit at 2.95 astronomical units from the black hole. However, this distance is inside the minimum stable orbit, so the planet would not be able to maintain that orbit around a non-rotating black hole. A rotating black hole could allow for a stable orbit at that distance. The paper also finds that travel times depicted in the film between the planet and a safe orbit are implausibly short.
General Relativity is Einstein's theory of gravitation that describes gravity as a result of the curvature of spacetime caused by the uneven distribution of mass/energy. It has been extensively tested and confirmed through observations of orbital precession, gravitational lensing, and gravitational redshift/time dilation. Black holes are a extreme prediction of GR where spacetime is so strongly curved that nothing, not even light, can escape once within the event horizon.
The document describes Hubble Space Telescope observations of Hercules A that revealed two faint, dark, interlocking rings of obscuring material located near the galaxy's nucleus and aligned along the radio jet axis. The rings are interpreted as either dust or electron scattering, and several models are discussed for their origin, including entrainment of molecular clouds by the radio jets or expansion of hot gas bubbles produced by the active galactic nucleus. The rings provide new insights into the transport of energy by powerful radio jets.
PROBING THE SOLAR INTERIOR WITH LENSED GRAVITATIONAL WAVES FROM KNOWN PULSARSSérgio Sacani
When gravitational waves (GWs) from a spinning neutron star arrive from behind the Sun, they are
subjected to gravitational lensing that imprints a frequency-dependent modulation on the waveform.
This modulation traces the projected solar density and gravitational potential along the path as
the Sun passes in front of the neutron star. We calculate how accurately the solar density prole
can be extracted from the lensed GWs using a Fisher analysis. For this purpose, we selected three
promising candidates (the highly spinning pulsars J1022+1001, J1730-2304, and J1745-23) from the
pulsar catalog of the Australia Telescope National Facility. The lensing signature can be measured
with 3 condence when the signal-to-noise ratio (SNR) of the GW detection reaches 100 (f=300Hz)1
over a one-year observation period (where f is the GW frequency). The solar density prole can be
plotted as a function of radius when the SNR improves to & 104.
Planetary system disruption_by_galactic _perturbations_to_wide_binary_starsSérgio Sacani
The document summarizes simulations showing that perturbations from the Milky Way can disrupt planetary systems in wide binary star systems (average separations over 1,000 AU) by driving variations in the binary orbit.
Specifically:
- Simulations found that 30-60% of planetary systems in wide binaries experience instabilities causing planetary ejections over 10 billion years due to low binary pericentre passages driven by Galactic tides.
- The eccentricity distribution of giant exoplanets in wide binaries is significantly higher than around single stars, consistent with additional scattering triggered by time-varying binary companions.
- Additional simulations reproduced the observed eccentricity distributions by assuming similar initial planetary systems that undergo scattering both in isolation and with a distant
Planetary system disruption by Galactic perturbations to wide binary starsCarlos Bella
1) Galactic perturbations cause the orbits of very widely separated binary stars (thousands of AU) to vary dramatically over billions of years, bringing the stars close together periodically.
2) Simulations show these close stellar passages in wide binaries can trigger planetary instabilities, ejecting planets from systems or exciting their orbital eccentricities.
3) The observed eccentricity distribution of exoplanets in wide binaries (separation >1,000 AU) matches this disruption scenario and is significantly higher than planets around single stars.
Probing the jet_base_of_blazar_pks1830211_from_the_chromatic_variability_of_i...Sérgio Sacani
This document summarizes ALMA observations of the blazar PKS 1830-211 taken over multiple epochs in 2012. The blazar is lensed by a foreground galaxy, producing two resolved images (NE and SW) separated by 1". The observations were taken at frequencies corresponding to 350-1050 GHz in the blazar rest frame. Analysis of the flux ratio between the two images over time and frequency revealed a remarkable frequency-dependent behavior, implying a "chromatic structure" in the blazar jet. This is interpreted as evidence for a "core-shift effect" caused by plasmon ejection very near the base of the jet. The observations provide a unique probe of activity in the region where plasma acceleration occurs in blazar
The deep blue_color_of_hd189733b_albedo_measurements_with_hst_stis_at_visible...Sérgio Sacani
The document summarizes a study that measured the geometric albedo of the exoplanet HD 189733b across visible wavelengths using Hubble Space Telescope observations. It found an albedo of 0.40 ± 0.12 at 290-450 nm that decreased to below 0.12 at 450-570 nm, suggesting optically thick clouds reflecting light at shorter wavelengths and sodium absorption suppressing reflection beyond 450 nm. This wavelength-dependent albedo implies HD 189733b would appear deep blue in color at visible wavelengths.
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
1) Astronomers observed comet Hale-Bopp at 30.7 AU from the Sun using the ESO 2.2m telescope in Chile on December 4, 2010.
2) They detected the comet with a total brightness of R=23.3 mag, corresponding to an absolute brightness of R(1,1,0)=8.3 mag.
3) The profile of the comet was star-like without any evidence of an extended coma or tail, indicating a cessation of matter production from the comet. However, the measured brightness corresponds to a reflecting surface area nine times smaller than three years prior, suggesting some low-level activity may still be occurring.
Search for the_exit_voyager1_at_heliosphere_border_with_the_galaxySérgio Sacani
Voyager 1 has detected changes in energetic particle intensities that suggest it has reached the outer boundary of the heliosphere and entered interstellar space. Measurements show a sudden decrease in particles of solar origin by over 100 times on August 25, 2012, while galactic cosmic rays increased by 9.3% at the same time. This indicates Voyager 1 has reached a region dominated by interstellar plasma rather than heated solar plasma. The spacecraft is now detecting unexpected anisotropies in cosmic rays and temporary increases that may be associated with large solar storms, implying it is still within a transitional region to the local interstellar medium.
Search for the Exit: Voyager 1 at Heliosphere’s Border with the Galaxy.Carlos Bella
Voyager 1 has detected changes in energetic particle intensities that suggest it has reached the outer boundary of the heliosphere and entered interstellar space. Measurements show a sudden decrease in particles of solar origin by over 100 times on August 25, 2012, while galactic cosmic rays increased by 9.3% at the same time. This indicates Voyager 1 has reached a region dominated by interstellar plasma rather than heated solar plasma. The spacecraft is now detecting unexpected anisotropies in cosmic rays and temporary increases that may be associated with large solar storms, implying it is still within a transitional region to the local interstellar medium.
Bright features have been recently discovered by Dawn on Ceres, which extend
previous photometric and Space Telescope observations. These features should produce
distortions of the line profiles of the reflected solar spectrum and therefore an apparent
radial velocity variation modulated by the rotation of the dwarf planet. Here we report
on two sequences of observations of Ceres performed in the nights of 31 July, 26-
27 August 2015 by means of the high-precision HARPS spectrograph at the 3.6-m
La Silla ESO telescope. The observations revealed a quite complex behaviour which
likely combines a radial velocity modulation due to the rotation with an amplitude of
⇡ ±6 m s
Similar to Science 2011-showalter-science.1202241 (20)
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
1. The Impact of Comet Shoemaker-Levy 9 Sends Ripples Through the Rings of Jupiter
Mark R. Showalter,1* Matthew M. Hedman,2 Joseph A. Burns2
1
SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043, USA. 2Cornell University, Ithaca NY 14853, USA.
*To whom correspondence should be addressed. E-mail: mshowalter@seti.org
Jupiter’s ring shows vertical corrugations reminiscent of the ring’s tip, where a radial vector is perpendicular to the
those recently detected in the rings of Saturn. The Galileo line of sight.
spacecraft imaged a pair of superimposed ripple patterns Note that the dependence of I on sin(θ) naturally predicts
in 1996 and again in 2000. These patterns behave as two the reversals of contrast observed in the Galileo image. We
independent spirals, each winding up at a rate defined by have applied Eq. 1 to derive the function Z′(R) at θ = 0 (Fig.
Jupiter’s gravity field. The dominant pattern originated 1C). Slopes approach 3% or ~1.5°. However, unlike the
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between July and October 1994, when the entire ring was pattern in Saturn’s rings (2, 3), this one is not a pure sinusoid;
tilted by ~2 km. We associate this with the Shoemaker- a Fourier transform shows two distinct peaks (Fig. 2A). In a
Levy 9 impacts of July 1994. New Horizons images still least-squares modeling of Z′(R), two sinusoids successfully
show this pattern 13 years later and suggest that account for the location of nearly every peak and trough.
subsequent events may also have tilted the ring. Impacts Matches to the amplitudes are imperfect, however, suggesting
by comets or their dust streams are regular occurrences that the ring slope may be modulated by other factors that we
in planetary rings, altering them in ways that remain have not yet considered. The dominant pattern has a
detectable decades later. wavelength λlong = 1920 ± 150 km and a vertical amplitude
Zlong = 2.4 ± 0.7 km; the shorter-wavelength pattern has λshort
On November 9, 1996, the Galileo spacecraft imaged a
= 630 ± 20 km and Zshort = 0.6 ± 0.2 km.
systematic, unexplained pattern of brightness variations in
If these sinusoidally varying slopes are analogous to the
Jupiter’s main ring, suggesting vertical ripples in the ring’s
corrugations observed at Saturn (2, 3), then they arose from
surface (1). More recently, Cassini images have revealed a
an initially tilted ring that slowly twisted into a spiral pattern
similar pattern in Saturn’s rings. That pattern arose from an
due to differential nodal regression. The wavelength of these
initially inclined ring, which was slowly twisted into a spiral
patterns depends only on the local gravitational field and the
by Saturn’s gravity (2, 3). A closer analysis of Galileo data
amount of time T that has elapsed since the ring became tilted
now confirms that the patterns in the rings of Jupiter and
(2, 3). Near the middle of the main Jovian ring, the predicted
Saturn obey identical kinematics, except that Jupiter’s ring
wavelength is
contains two ripple patterns, not one.
λ = ~4200 km / (T/years) (2)
Galileo viewed the rings from nearly edge-on, with
opening angle B = 0.48° (Fig. 1 and table S1). The intensity I
The numerical factor is derived from Jupiter’s gravitational
of an optically thin ring is proportional to the amount of
harmonics (8). It varies by ~15% within the radial limits
material along the line of sight, so it varies as sin(B)–1. For the
considered but, for practical purposes, can be treated as a
Jovian ring, optical depth τ < 10–5 (4, 5), so this dependence
constant when modeling individual profiles (6).
applies. In this limit, the Sun’s opening angle plays no role,
Compared to Saturn’s ~30-km periodicity, the longer
because every particle is illuminated equally.
wavelengths at Jupiter would imply much younger features.
A nonzero surface slope modifies the effective local
For the long-wavelength pattern, T = 800 ± 60 days,
opening angle, naturally leading to variations in I (6):
indicating that a ring-tilting event occurred between July 1
and November 1, 1994. The shorter wavelength corresponds
I 1 / sin(B) [1 - sin(θ)/sin(B) Z′(R,θ)] (1)
to T = 2430 ± 80 days, meaning that the feature originated
between early January and early June, 1990; the midpoint is
Here, Z(R,θ) describes the local height of the ring above the
March 19.
equatorial plane in polar coordinates (R,θ). The radial
Two Galileo images from June 21, 2000 confirm that this
component of the local slope is Z′(R,θ) ≡ ∂Z/∂R; we neglect
pattern is evolving in the predicted manner. The images
the slope’s much smaller tangential component (6, 7).
individually have very poor signal-to-noise properties, and
Longitudes are measured from the ansa line passing through
charged particle impacts into the camera’s CCD corrupt many
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2. pixels (fig. S1). Nevertheless, combined processing of both know where to position the center of SL9’s mass prior to its
images has enabled us to identify and eliminate most of the breakup (10, 11). Thus, we cannot rule out the possibility that
corrupted pixels (Fig. 3A). Contrast reversals show up clearly SL9 triggered the 1990 pattern, although it must have passed
after processing (Fig. 3B), from which we have derived Z′(R) much closer to the ring than it did in 1992. Alternatively, the
(Fig. 3C). Fourier processing once more identifies two secondary pattern may have been triggered by a different,
dominant peaks, but now they are at shorter wavelengths unseen comet; this hypothesis is generally compatible with
(Fig. 2B). Modeling of the ring profile as a superposition of more recent, higher estimates for the frequency of impacts
two sinusoids provides a very good description of the data (9). History records other very close passages of Jupiter by
(Fig. 3C, dashed line), with λlong = 695 ± 55 km; Zlong = 1.8 ± comets 16P/Brooks 2 in 1886 and P/Gehrels 3 in 1970 (12).
0.4 km; λshort = 414 ± 20 km; Zshort = 0.6 ± 0.2 km. For What mechanism might have enabled SL9 to alter the
comparison, if we use Eq. 2 to extrapolate the patterns seen in Jovian ring so dramatically? In 1994, SL9’s solid fragments
1996 forward over the intervening 1289 days, we would entered Jupiter at southern latitudes on a north-bound
expect λlong = 734 km and λshort = 412 km. Thus, the trajectory; they never reached the ring plane. However, dust
wavelengths and amplitudes seen in 2000 are consistent with grains associated with SL9’s fragments could have been
the expected rate of winding of these spiral features. deflected past the planet and into the ring by solar radiation
To complete our data analysis, we examined four images pressure (Fig. 4) (6). Others have explored the effects of
taken just before New Horizons crossed the Jovian ring plane radiation pressure on SL9’s dust (13, 14), but not with an eye
Downloaded from www.sciencemag.org on March 31, 2011
on March 1, 2007 (figs. S2 to S4). Fourier analysis reveals the toward the consequences for the ring system. We define β as
continuing effects of SL9’s impact (Fig. 2C). Although Zlong the ratio of radiation pressure to solar gravity (15).
has diminished to ~350 km, this detection attests to the Integrations show that grains with β = 0.007 (radius ≈ 50
features’ longevity. The shorter pattern can no longer be μm), if released at the time of the 1992 perijove and breakup,
detected. However, two suggestive new patterns appear, with would be deflected directly into the main ring in 1994 (6).
λ ≈ 1315 km and 775 km (fig. S4C). If confirmed by later Larger grains can never intercept the ring but smaller ones, if
detections, these would indicate that the rings received released later, can. The fragments were emitting dust
additional km-scale tilts around September 2001 and continuously between the 1992 breakup and the 1994 impact
December 2003. (14, 16), providing a continuous source of potential ring
A suitable explanation for ring-tilting events must satisfy impactors. Regardless of their ejection date, integrations
some very specific requirements. First, each event must occur show that all particles crossing the main Jovian ring do so
within a very brief time span (2, 3). The nodal regression rate within the same ~10° sector of inertial longitude and within a
for orbits in the main Jovian ring is 8.5°/day, enough to smear time span of a few days (6); thus, they naturally satisfy the
out the effects of any event lasting more than a few weeks. requirement to offset the ring quickly and systematically.
Second, these events must be infrequent, with 2–4 Because Jupiter’s ring is optically thin, every ring
occurrences between ~1985 and ~2006. Within this context, it constituent responds independently to the influx of cometary
is natural to associate the long pattern with the SL9 impacts dust. To tilt an orbit by 2 km requires that, on average,
of July 16–20, 1994. They occurred within the identified particles intercept ~10–6 of their own mass (6). For a ring of
window spanning July–October. Although SL9 was earlier 1-cm particles spanning the orbits of Metis and Adrastea
regarded as a “once a century” impact, the observed collision (128,000–129,000 km), an integrated fluence of ~10–6 g/cm2
of another object into Jupiter on July 19, 2009 suggests that would be required, or ~1013 g in total. Our simulations
such events may be 5–10 times more frequent than previously indicate that 0.2–0.5% of SL9’s ejecta smaller than 50 μm
thought (9). The chance of one occurring at random within will intercept this ring (6). We therefore require SL9 to
the identified four-month window is 1–3%. produce ~2–5 × 1015 g of dust, amounting to a volume ~2–5
The triggering event for the secondary pattern in Galileo km3. For comparison, estimates of the initial diameter of the
images is less clear. SL9 fractured during its prior perijove on intact comet range from D ~ 1.5 km (17) to 10 km (18).
July 7, 1992. It crossed the equator at R ~ 115,000 km (10), Corresponding volume estimates are V = 2–500 km3. A meta-
apparently producing no measurable effect on the ring less study (19) concludes D = 3.5 km (V ≈ 20 km3). The
than 15,000 km further out. The perijove before that was in fragments of SL9 underwent substantial collisional evolution
mid-1990, within the window defined by the short shortly after the breakup (13); this can lead to a steep size
wavelength and raising the possibility that SL9 triggered this distribution in which a substantial fraction of the mass is
pattern as well. However, backward integrations of SL9’s concentrated in the smallest particles. If so, then the larger
trajectory place this perijove much further from Jupiter (10, estimates for SL9’s volume are compatible with our
11). Such integrations have large uncertainties, arising from requirements. Our results are difficult to reconcile with the
the chaotic nature of SL9’s orbit, and because we do not
/ www.sciencexpress.org / 31 March 2011 / Page 2 / 10.1126/science.1202241
3. smallest size estimates, which are based on dynamical models 8. R. A. Jacobson, The gravity field of the Jovian system and
of how a loosely-bound rubble pile would break apart (17). the orbits of the regular Jovian satellites, Bull. Amer.
For a given fluence of cometary dust, larger ring bodies Astron. Soc. 33, 1039 (2001).
are deflected to smaller tilt angles in inverse proportion to 9. A. Sánchez-Lavega et al., The impact of a large object on
their radii. We chose 1 cm for the above calculation because Jupiter in 2009 July, Astrophys. J. 715, L155 (2010).
cm-sized particles are likely to achieve the largest tilts; 10. L. A. Benner, W. B. McKinnon, On the orbital evolution
smaller particles can be shattered by the 50-μm impactors (6). and origin of comet Shoemaker-Levy 9, Icarus 118, 155
Thus, our mass estimate is only valid if the size distribution is (1995).
steep, so that the ring’s appearance is dominated by the 11. P. W. Chodas, D. K. Yeomans, The orbital motion and
smallest surviving particles (and their ejecta). The Jovian impact circumstances of comet Shoemaker-Levy 9, in The
ring’s dust population does steepen markedly above ~30 μm Collision of Comet Shoemaker-Levy 9 and Jupiter, K. S.
(5), suggesting that this assumption is plausible. Noll, H. A. Weaver, P. D. Feldman, Eds. (Cambridge
The kinematics of these spirals requires that the Univ. Press, 1996), pp. 1–30.
wavelength be nearly uniform at any given time, but the tilts 12. K. Zahnle, L. Dones, H. F. Levison, Cratering rates on the
need not be. In an optically thin ring, they will vary Galilean satellites, Icarus 136, 202 (1998).
depending on the local ring particle sizes. In Fig. 1C, the 13. Z. Sekanina, P. W. Chodas, D. W. Yeomans, Tidal
inward decrease of the slopes may simply indicate a disruption and the appearance of periodic comet
Downloaded from www.sciencemag.org on March 31, 2011
decreasing population of the cm-sized particles. This is Shoemaker-Levy 9, Astrophys. J. 289, 607 (1994).
consistent with ring photometry that indicates a rapidly 14. J. M. Hahn, T. W. Rettig, Comet Shoemaker-Levy 9 dust
decreasing number of embedded macroscopic bodies interior size and velocity distributions, Icarus 146, 501 (2000).
to the orbit of Metis (20, 21). 15. J. A. Burns, P. L. Lamy, S. Soter, Radiation forces on
We now recognize that impacts by comets and/or their small particles in the Solar System, Icarus 40, 1 (1979).
dust clouds are common occurrences in planetary rings. On at 16. H. A. Weaver et al., Hubble Space Telescope
least three occasions over the last few decades, these observations of comet P/Shoemaker-Levy 9 (1993e),
collisions have carried sufficient momentum to tilt a ring of Science 263, 787 (1994).
Jupiter or Saturn off its axis by an observable distance. Once 17. E. Asphaug, W. Benz, Size, density, and structure of
such a tilt is established, it can persist for decades, with the comet Shoemaker-Levy 9 inferred from the physics of
passage of time recorded in its ever-tightening spiral. Within tidal breakup, Icarus 121, 225 (1996).
these subtle patterns, planetary rings chronicle their own 18. Z. Sekanina, P. W. Chodas, D. K. Yeomans, Secondary
battered histories. fragmentation of comet Shoemaker-Levy 9 and the
ramifications for the progenitor’s breakup in July 1992,
References and Notes Plan. Space Sci. 46, 21 (1998).
1. M. Ockert-Bell et al., The structure of Jupiter’s ring system 19. M. Zamarashkina, Y. Medvedev, Dynamics of comet
as revealed by the Galileo imaging experiment, Icarus Shoemaker-Levy 9, Proc. of ACM 500, 457 (2002).
138, 188 (1999). 20. J. A. Burns et al., Jupiter’s Ring-Moon System, in
2. M. M. Hedman et al., Saturn’s dynamic D ring, Icarus 188, Jupiter: The Planet, Satellites and Magnetosphere, F.
89 (2007). Bagenal, Eds. (Cambridge Univ. Press, 2004), pp. 241–
3. M. M. Hedman, J. A. Burns, M. W. Evans, M. S. 262.
Tiscareno, C. C. Porco, Saturn’s curiously corrugated C 21. M. R. Showalter et al., Clump detections and limits on
ring, Science, posted online 31 March 2011; moons in Jupiter’s ring system, Science 318, 232 (2007).
10.1126/science.1202238. Acknowledgments: M.R.S. acknowledges the support of
4. M. R. Showalter, J. A. Burns, J. N. Cuzzi, J. B. Pollack, NASA’s Jupiter Data Analysis Program through grant
Jupiter’s ring system: New results on structure and particle NNX09AD97G. J.A.B. has been funded by NASA’s
properties, Icarus 69, 458 (1987). Planetary Geology and Geophysics Program.
5. S. M. Brooks, L. W. Esposito, M. R. Showalter, H. B.
Throop, The size distribution in Jupiter’s main ring from Supporting Online Material
Galileo imaging and spectroscopy, Icarus 170, 35 (2004). www.sciencemag.org/cgi/content/full/science.1202241/DC1
6. Information on materials, methods, and models is available Materials and Methods
on Science Online. Figs. S1 to S5
7. This formula is only valid where both sin(B) and Table S1
sin(θ)/sin(B) Z′(R,θ) are << 1; these constraints are References 22 and 23
satisfied throughout our analysis.
/ www.sciencexpress.org / 31 March 2011 / Page 3 / 10.1126/science.1202241
4. 27 December 2010; accepted 16 March 2011
Published online 31 March 2011; 10.1126/science.1202241
Fig. 1. (A) Galileo image C0368974139 from November 9,
1996 shows the Jovian ring’s tip. Indicated are the directions
in which longitude θ and radius R are measured. (B) We
expanded the image vertically, co-added two similar frames
for improved signal-to-noise, and subtracted a duplicate of
the image after reversing it top-to-bottom. Most of the image
nearly cancels itself out, but the signals of the ripples are
reinforced. Neutral gray corresponds to zero; darker areas are
negative. (C) A derived profile of the ring’s surface slope vs.
radius (solid line). For comparison, the dashed line shows a
fit involving superimposed patterns triggered on July 19,
1994 and March 19, 1990. In this fit, we have neglected the
expected variation in λ with R (6). Note that panels (A) to (C)
have been aligned vertically to employ the same
Downloaded from www.sciencemag.org on March 31, 2011
radial/horizontal scale.
Fig. 2. Fourier transforms of each radial profile of the ring’s
surface slope, Z′(R). Data are from Galileo in 1996 (A) and
2000 (B), and from New Horizons in 2007 (C). Vertical lines
mark the expected wavenumber (1/λ) for features triggered on
July 19, 1994 (dashed) and on March 19, 1990 (dotted). On
the vertical axes, the Fourier amplitude values roughly
indicate the height of a single sinusoid, of fixed wavelength
but variable phase, that best fits the profile.
Fig. 3. (A) Two Galileo images from 2000 have been overlaid
and combined to produce a clear image of the ring’s ansa (6).
(B) After flipping the image vertically and subtracting,
enhancement reveals the pattern of contrast reversals
indicating vertical undulations. (C) A derived radial profile of
the ring’s slope (solid line). For comparison, the dashed line
is a best fit using two sinusoidal patterns, with wavelengths
defined by our assumed trigger dates of July 19, 1994 and
March 19, 1990. The three panels have been aligned to
employ the same radial scale; note that this scale is much
smaller than that in Fig. 1.
Fig. 4. The influence of solar radiation pressure on the motion
of SL9’s fragments is shown as a function of β. Integrations
assume that the pieces separated at low relative velocity
during the 1992 perijove. The heavy arrow (β = 0) shows the
path of the large, observed fragments. The trajectories of
smaller particles are displaced leftward in the diagram;
corresponding β values are labeled around the periphery.
Particles with β ≈ 0.007 (heavy dashed line) impact the main
ring.
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