After the Moon’s formation, Earth experienced a protracted bombardment by leftover planetesimals. The mass delivered during
this stage of late accretion has been estimated to be approximately 0.5% of Earth’s present mass, based on highly siderophile
element concentrations in the Earth’s mantle and the assumption that all highly siderophile elements delivered by impacts
were retained in the mantle. However, late accretion may have involved mostly large (≥ 1,500 km in diameter)—and therefore
differentiated—projectiles in which highly siderophile elements were sequestered primarily in metallic cores. Here we present
smoothed-particle hydrodynamics impact simulations that show that substantial portions of a large planetesimal’s core may
descend to the Earth’s core or escape accretion entirely. Both outcomes reduce the delivery of highly siderophile elements to
the Earth’s mantle and imply a late accretion mass that may be two to five times greater than previously thought. Further, we
demonstrate that projectile material can be concentrated within localized domains of Earth’s mantle, producing both positive
and negative 182W isotopic anomalies of the order of 10 to 100 ppm. In this scenario, some isotopic anomalies observed in terrestrial
rocks can be explained as products of collisions after Moon formation.
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.
Mars surface radiation_environment_measured_with_curiositySérgio Sacani
The Radiation Assessment Detector on the Curiosity rover measured the radiation environment on the surface of Mars over approximately 300 days. It found:
1) The average absorbed radiation dose from galactic cosmic rays was 0.210 mGy/day, varying due to atmospheric and solar conditions.
2) An additional absorbed dose of about 50 μGy was measured from a solar particle event.
3) Extrapolating the surface measurements, the absorbed dose was estimated to be 76 mGy/year at 1 meter below the surface, decreasing substantially at greater depths.
The document describes simulations of a collision between the Moon and a companion moon approximately 1/3 the diameter of the Moon. The simulations found that at the modeled subsonic impact velocity, the companion moon did not form an impact crater but was instead accreted onto the Moon's surface. This added material contributed a hemispheric layer comparable to the extent and thickness of the lunar farside highlands. The collision also displaced the Moon's magma ocean to the opposite hemisphere, potentially explaining the observed concentration of KREEP materials. The findings suggest this late accretion event could explain the geological dichotomy between the lunar near and farside regions.
The asteroid belt contains less than a thousandth of Earth’s mass and is radially segregated, with S-types
dominating the inner belt and C-types the outer belt. It is generally assumed that the belt formed with far more
mass and was later strongly depleted. We show that the present-day asteroid belt is consistent with having
formed empty, without any planetesimals between Mars and Jupiter’s present-day orbits. This is consistent with
models in which drifting dust is concentrated into an isolated annulus of terrestrial planetesimals. Gravitational
scattering during terrestrial planet formation causes radial spreading, transporting planetesimals from inside
1 to 1.5 astronomical units out to the belt. Several times the total current mass in S-types is implanted, with a
preference for the inner main belt. C-types are implanted from the outside, as the giant planets’ gas accretion
destabilizes nearby planetesimals and injects a fraction into the asteroid belt, preferentially in the outer main
belt. These implantation mechanisms are simple by-products of terrestrial and giant planet formation. The asteroid
belt may thus represent a repository for planetary leftovers that accreted across the solar system but not
in the belt itself.
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.
Mars surface radiation_environment_measured_with_curiositySérgio Sacani
The Radiation Assessment Detector on the Curiosity rover measured the radiation environment on the surface of Mars over approximately 300 days. It found:
1) The average absorbed radiation dose from galactic cosmic rays was 0.210 mGy/day, varying due to atmospheric and solar conditions.
2) An additional absorbed dose of about 50 μGy was measured from a solar particle event.
3) Extrapolating the surface measurements, the absorbed dose was estimated to be 76 mGy/year at 1 meter below the surface, decreasing substantially at greater depths.
The document describes simulations of a collision between the Moon and a companion moon approximately 1/3 the diameter of the Moon. The simulations found that at the modeled subsonic impact velocity, the companion moon did not form an impact crater but was instead accreted onto the Moon's surface. This added material contributed a hemispheric layer comparable to the extent and thickness of the lunar farside highlands. The collision also displaced the Moon's magma ocean to the opposite hemisphere, potentially explaining the observed concentration of KREEP materials. The findings suggest this late accretion event could explain the geological dichotomy between the lunar near and farside regions.
The asteroid belt contains less than a thousandth of Earth’s mass and is radially segregated, with S-types
dominating the inner belt and C-types the outer belt. It is generally assumed that the belt formed with far more
mass and was later strongly depleted. We show that the present-day asteroid belt is consistent with having
formed empty, without any planetesimals between Mars and Jupiter’s present-day orbits. This is consistent with
models in which drifting dust is concentrated into an isolated annulus of terrestrial planetesimals. Gravitational
scattering during terrestrial planet formation causes radial spreading, transporting planetesimals from inside
1 to 1.5 astronomical units out to the belt. Several times the total current mass in S-types is implanted, with a
preference for the inner main belt. C-types are implanted from the outside, as the giant planets’ gas accretion
destabilizes nearby planetesimals and injects a fraction into the asteroid belt, preferentially in the outer main
belt. These implantation mechanisms are simple by-products of terrestrial and giant planet formation. The asteroid
belt may thus represent a repository for planetary leftovers that accreted across the solar system but not
in the belt itself.
The document summarizes numerical simulations of magma convection and mixing dynamics in volcanic systems. The simulations reveal unexpected pressure trends and oscillations in the Ultra-Long-Period (ULP) range of minutes related to the generation of rising magma plumes. These very long pressure oscillations can translate to comparable ULP ground displacements at the surface with amplitudes of 10-4 to 10-2 meters. Therefore, new magma injection into shallow magma chambers beneath volcanoes may be revealed by measuring ULP ground displacement.
On the theory_and_future_cosmic_planet_formationSérgio Sacani
A Terra chegou cedo para a festa no universo em evolução. De acordo com um novo estudo teórico, quando o nosso Sistema Solar nasceu a 4.6 bilhões de anos atrás, somente 8% dos planetas possivelmente habitáveis que serão formados no universo, existiam. E, a festa não terminaria até quando o Sol queimasse por outros 6 bilhões de anos. A totalidade desses planetas, 92%, não tinham nascido.
Essa conclusão é baseada no acesso dos dados coletados pelo Telescópio Espacial Hubble da NASA e o prolífico caçador de exoplanetas, o Observatório Espacial Kepler.
“Nossa principal motivação foi entender o lugar da Terra no contexto do resto do universo”, disse o autor do estudo Peter Behroozi do Space Telescope Science Institute (STScI), em Baltimore, Maryland, “Comparado a todos os planetas que irão se formar no universo, a Terra, na verdade chegou cedo”.
Olhando distante no espaço e no tempo, o Hubble, tem dado aos astrônomos um verdadeiro “álbum de família”, das observações da galáxia que mostra a história da formação do universo à medida que as galáxias cresciam. Os dados mostram que o universo estava gerando estrelas numa taxa elevada a 10 bilhões de anos atrás, mas a fração do gás hidrogênio e hélio do universo que estava envolvida era muito baixa. Hoje, o nascimento de estrelas está acontecendo numa taxa muito mais lenta do que a muito tempo atrás, mas existe muito gás deixado para trás disponível que o universo continuará gerando estrelas e planetas por muito tempo ainda.
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.
1) High-resolution gravity data from NASA's GRAIL mission shows distinctive "bulls-eye" patterns of gravity anomalies over lunar impact basins, with a central positive anomaly surrounded by a negative collar and outer positive annulus.
2) The document uses hydrocode modeling and finite element modeling to show that these mascon gravity patterns naturally result from the excavation and collapse of an impact crater, followed by post-impact isostatic adjustment and cooling/contraction of the melt pool.
3) The modeling is able to replicate the observed gravity anomalies of the Freundlich-Sharanov and Humorum basins, supporting the theory that mascons form through this impact and relaxation process rather than
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.
This document discusses evidence that the Moon-forming impact occurred later than previously thought, at around 95 million years after the formation of the solar system. The study uses simulations of planetary formation to show a correlation between the timing of the last giant impact and the amount of mass later accreted by the planet. Comparing this to highly siderophile element abundances in Earth's mantle, which constrain the amount of late-accreted mass, the study determines the Moon-forming impact was most likely 95 million years after solar system formation. Earlier times of 40 million years or less are ruled out at a 99.9% confidence level. The simulations include both classical scenarios and scenarios where Jupiter and Saturn migrated inward early in the solar
A precise water_abundance_measurement_for_the_hot_jupiter_wasp_43bSérgio Sacani
This document presents a precise measurement of the water abundance in the atmosphere of the exoplanet WASP-43b using transmission and thermal emission spectroscopy from the Hubble Space Telescope. The key findings are:
1) The water content of WASP-43b's atmosphere is consistent with solar composition at planetary temperatures, ranging from 0.4 to 3.5 times the solar water abundance.
2) This metallicity measurement extends the trend seen in the solar system of lower metal enrichment for higher mass planets.
3) Measuring a planet's water content constrains its formation location in the protoplanetary disk and provides insight into planetary formation models.
- Gravity and magnetic mapping techniques measure small variations in the Earth's gravity and magnetic fields to infer properties of subsurface geology.
- Gravity mapping uses highly sensitive spring balances called gravimeters to detect variations as small as 0.001 mgal, while magnetic mapping uses electronic instruments to continuously record magnetic field variations.
- Corrections must be applied to gravity and magnetic data to account for factors like latitude, elevation, density variations, and temporal changes in the magnetic field.
- Interpretation of the residual anomaly maps provides constraints on the locations, shapes, and depths of subsurface density and magnetic sources, allowing inference of geological structures.
(1) The document presents a theoretical question about when the Moon will become a synchronous satellite. It provides background information on the tidal forces acting between the Earth and Moon, and how these are slowing the Earth's rotation over time.
(2) The question asks the reader to calculate the total angular momentum of the current Earth-Moon system, the duration of a full Earth rotation when it becomes synchronous with the Moon's orbit, and the estimated time in years until synchronization occurs.
(3) It provides various data on physical properties of the Earth and Moon, assumptions that can be made, and mathematical formulas that may be useful in solving the questions. Diagrams are also included to illustrate the system and tidal model being
1) Geophysical surveys have been using measurements of the Earth's magnetic field for nearly 500 years since Gilbert showed that the Earth behaves like a large magnet.
2) Gravity and magnetic surveying methods are similar in that they both measure naturally occurring fields (potential fields), can use identical physical representations like magnetic monopoles, and have similar data acquisition and interpretation.
3) However, magnetic surveying also has differences from gravity - magnetic susceptibility of rocks can vary more than density, magnetism can be attractive or repulsive unlike gravity, magnetic sources always occur in pairs unlike gravity, and the magnetic field is time-dependent unlike gravity.
This document presents a probabilistic model for forecasting the duration of volcanic eruptions based on analyzing historical duration data. It focuses on developing a dataset of eruption durations for flank eruptions at Mount Etna between 1300-2010 AD. The data is compiled from existing literature and considers durations reliable after 1600 due to potential reporting biases earlier. The durations are fit to theoretical probability distributions to generate forecasts of future eruption durations, such as the probability of an eruption exceeding a given number of days. The model is demonstrated on Mount Etna data and can be adapted for other volcanoes.
How common are earth moon planetary systemsSérgio Sacani
This document discusses the frequency of Earth-moon type planetary systems based on simulations of terrestrial planet formation. It first reviews how simulations of planet formation have improved over time to model more particles over longer timescales. It then examines parameters from a large set of simulations to identify collisions that could result in circumplanetary disks and satellite formation. The authors find that such moon-forming impacts occur in about 1 in 12 to 1 in 4 simulations, suggesting Earth-moon systems may be relatively common around other terrestrial planets.
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.
O centro da nossa Via Láctea é um lugar misterioso. Não somente está a milhares de anos-luz de distância, mas está também escondido sob grande quantidade de poeira de modo que a maior parte das estrelas em seu interior são invisíveis. Pesquisadores de Harvard, estão propondo uma nova maneira de limpar a neblina e registrar as estrelas ali escondidas. Eles sugerem observar os comprimentos de onda de rádio provenientes das estrelas supersônicas.
“Existem muitas, nós não sabemos sobre o centro galáctico, e nós queremos aprender muito”, disse o principal autor do estudo Idan Ginsburg do Harvard-Smithsonian Center for Astrophysics (CfA). “Usando essa técnica, nós podemos encontrar estrelas que ninguém observou antes”.
A grande trajetória do centro da nossa galáxia para a Terra é repleta de tanta poeira que até mesmo dos trilhões de fótons de luz visível que veem em nossa direção, somente um fóton atingirá nossos telescópios. Ondas de rádio, de uma diferente parte do espectro eletromagnético, possui energia mais baixa e comprimentos de onda maiores. Elas podem passar pela poeira de forma ilesa.
Very regular high-frequency pulsation modes in young intermediate-mass starsSérgio Sacani
Asteroseismology probes the internal structures of stars by using their natural
pulsation frequencies1. It relies on identifying sequences of pulsation modes that can
be compared with theoretical models, which has been done successfully for many
classes of pulsators, including low-mass solar-type stars2, red giants3, high-mass stars4
and white dwarfs5. However, a large group of pulsating stars of intermediate mass—the
so-called δ Scuti stars—have rich pulsation spectra for which systematic mode
identification has not hitherto been possible6,7. This arises because only a seemingly
random subset of possible modes are excited and because rapid rotation tends to
spoil regular patterns8–10. Here we report the detection of remarkably regular
sequences of high-frequency pulsation modes in 60 intermediate-mass
main-sequence stars, which enables definitive mode identification. The space
motions of some of these stars indicate that they are members of known associations
of young stars, as confirmed by modelling of their pulsation spectra.
The document describes a study that tested the shear strength of clay soil samples from the Rattlesnake Gulf landslide in New York's Tully Valley. The study used an Autoshear device to measure shear stress, vertical displacement, and horizontal load in order to analyze shear strength parameters. The results will help understand what makes the area susceptible to landslides and inform slope stability analysis. A literature review covers concepts of slope stability, shear strength testing, and factors influencing landslides in the Tully Valley region.
This document presents a non-extensive model for the frequency-magnitude distribution of earthquakes based on Tsallis entropy. The model assumes fragments between fault planes play an active role in triggering earthquakes. By applying maximum entropy principle with Tsallis entropy, the model derives an explicit function relating earthquake energy distribution to fragment size distribution. The function describes earthquake energy distributions over a wide range of energies. Analysis of earthquake data from southern Spain shows the model fits the data better than traditional Boltzmann statistics-based models, particularly for smaller magnitudes where other models fail.
Molecular gas clumps_from_the_destruction_of_icy_bodies_in_beta_pictoris_debr...Sérgio Sacani
1) ALMA observations detected carbon monoxide gas orbiting in a debris disk around the young star Beta Pictoris, with a total mass equivalent to 0.0023 times the mass of Earth's Moon.
2) The gas is distributed asymmetrically, with 30% located in a single clump 85 AU from the star. This gas clump is aligned with the orbit of an inner planet in the system.
3) The gas must be continuously replenished, likely from the destruction of icy planetesimals and comets through collisions within the debris disk. The collisions may be enhanced in the gas clump due to resonances with an unseen giant planet or from remnants of a large collision between
Molecular Gas Clumps from the Destruction of Icy Bodies in the β Pictoris Deb...GOASA
1) ALMA observations detected carbon monoxide gas orbiting in a debris disk around the young star Beta Pictoris, with a total mass equivalent to 0.0023 times the mass of Earth's Moon.
2) The gas is distributed asymmetrically, with 30% located in a single clump 85 AU from the star. This gas clump is aligned with the orbit of an inner planet in the system.
3) The gas must be continuously replenished, likely from the destruction of icy planetesimals and comets through collisions within the debris disk. The collisions may be enhanced in the gas clump due to resonances with an unseen giant planet or the remnants of a large collision between
The document summarizes numerical simulations of magma convection and mixing dynamics in volcanic systems. The simulations reveal unexpected pressure trends and oscillations in the Ultra-Long-Period (ULP) range of minutes related to the generation of rising magma plumes. These very long pressure oscillations can translate to comparable ULP ground displacements at the surface with amplitudes of 10-4 to 10-2 meters. Therefore, new magma injection into shallow magma chambers beneath volcanoes may be revealed by measuring ULP ground displacement.
On the theory_and_future_cosmic_planet_formationSérgio Sacani
A Terra chegou cedo para a festa no universo em evolução. De acordo com um novo estudo teórico, quando o nosso Sistema Solar nasceu a 4.6 bilhões de anos atrás, somente 8% dos planetas possivelmente habitáveis que serão formados no universo, existiam. E, a festa não terminaria até quando o Sol queimasse por outros 6 bilhões de anos. A totalidade desses planetas, 92%, não tinham nascido.
Essa conclusão é baseada no acesso dos dados coletados pelo Telescópio Espacial Hubble da NASA e o prolífico caçador de exoplanetas, o Observatório Espacial Kepler.
“Nossa principal motivação foi entender o lugar da Terra no contexto do resto do universo”, disse o autor do estudo Peter Behroozi do Space Telescope Science Institute (STScI), em Baltimore, Maryland, “Comparado a todos os planetas que irão se formar no universo, a Terra, na verdade chegou cedo”.
Olhando distante no espaço e no tempo, o Hubble, tem dado aos astrônomos um verdadeiro “álbum de família”, das observações da galáxia que mostra a história da formação do universo à medida que as galáxias cresciam. Os dados mostram que o universo estava gerando estrelas numa taxa elevada a 10 bilhões de anos atrás, mas a fração do gás hidrogênio e hélio do universo que estava envolvida era muito baixa. Hoje, o nascimento de estrelas está acontecendo numa taxa muito mais lenta do que a muito tempo atrás, mas existe muito gás deixado para trás disponível que o universo continuará gerando estrelas e planetas por muito tempo ainda.
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.
1) High-resolution gravity data from NASA's GRAIL mission shows distinctive "bulls-eye" patterns of gravity anomalies over lunar impact basins, with a central positive anomaly surrounded by a negative collar and outer positive annulus.
2) The document uses hydrocode modeling and finite element modeling to show that these mascon gravity patterns naturally result from the excavation and collapse of an impact crater, followed by post-impact isostatic adjustment and cooling/contraction of the melt pool.
3) The modeling is able to replicate the observed gravity anomalies of the Freundlich-Sharanov and Humorum basins, supporting the theory that mascons form through this impact and relaxation process rather than
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.
This document discusses evidence that the Moon-forming impact occurred later than previously thought, at around 95 million years after the formation of the solar system. The study uses simulations of planetary formation to show a correlation between the timing of the last giant impact and the amount of mass later accreted by the planet. Comparing this to highly siderophile element abundances in Earth's mantle, which constrain the amount of late-accreted mass, the study determines the Moon-forming impact was most likely 95 million years after solar system formation. Earlier times of 40 million years or less are ruled out at a 99.9% confidence level. The simulations include both classical scenarios and scenarios where Jupiter and Saturn migrated inward early in the solar
A precise water_abundance_measurement_for_the_hot_jupiter_wasp_43bSérgio Sacani
This document presents a precise measurement of the water abundance in the atmosphere of the exoplanet WASP-43b using transmission and thermal emission spectroscopy from the Hubble Space Telescope. The key findings are:
1) The water content of WASP-43b's atmosphere is consistent with solar composition at planetary temperatures, ranging from 0.4 to 3.5 times the solar water abundance.
2) This metallicity measurement extends the trend seen in the solar system of lower metal enrichment for higher mass planets.
3) Measuring a planet's water content constrains its formation location in the protoplanetary disk and provides insight into planetary formation models.
- Gravity and magnetic mapping techniques measure small variations in the Earth's gravity and magnetic fields to infer properties of subsurface geology.
- Gravity mapping uses highly sensitive spring balances called gravimeters to detect variations as small as 0.001 mgal, while magnetic mapping uses electronic instruments to continuously record magnetic field variations.
- Corrections must be applied to gravity and magnetic data to account for factors like latitude, elevation, density variations, and temporal changes in the magnetic field.
- Interpretation of the residual anomaly maps provides constraints on the locations, shapes, and depths of subsurface density and magnetic sources, allowing inference of geological structures.
(1) The document presents a theoretical question about when the Moon will become a synchronous satellite. It provides background information on the tidal forces acting between the Earth and Moon, and how these are slowing the Earth's rotation over time.
(2) The question asks the reader to calculate the total angular momentum of the current Earth-Moon system, the duration of a full Earth rotation when it becomes synchronous with the Moon's orbit, and the estimated time in years until synchronization occurs.
(3) It provides various data on physical properties of the Earth and Moon, assumptions that can be made, and mathematical formulas that may be useful in solving the questions. Diagrams are also included to illustrate the system and tidal model being
1) Geophysical surveys have been using measurements of the Earth's magnetic field for nearly 500 years since Gilbert showed that the Earth behaves like a large magnet.
2) Gravity and magnetic surveying methods are similar in that they both measure naturally occurring fields (potential fields), can use identical physical representations like magnetic monopoles, and have similar data acquisition and interpretation.
3) However, magnetic surveying also has differences from gravity - magnetic susceptibility of rocks can vary more than density, magnetism can be attractive or repulsive unlike gravity, magnetic sources always occur in pairs unlike gravity, and the magnetic field is time-dependent unlike gravity.
This document presents a probabilistic model for forecasting the duration of volcanic eruptions based on analyzing historical duration data. It focuses on developing a dataset of eruption durations for flank eruptions at Mount Etna between 1300-2010 AD. The data is compiled from existing literature and considers durations reliable after 1600 due to potential reporting biases earlier. The durations are fit to theoretical probability distributions to generate forecasts of future eruption durations, such as the probability of an eruption exceeding a given number of days. The model is demonstrated on Mount Etna data and can be adapted for other volcanoes.
How common are earth moon planetary systemsSérgio Sacani
This document discusses the frequency of Earth-moon type planetary systems based on simulations of terrestrial planet formation. It first reviews how simulations of planet formation have improved over time to model more particles over longer timescales. It then examines parameters from a large set of simulations to identify collisions that could result in circumplanetary disks and satellite formation. The authors find that such moon-forming impacts occur in about 1 in 12 to 1 in 4 simulations, suggesting Earth-moon systems may be relatively common around other terrestrial planets.
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.
O centro da nossa Via Láctea é um lugar misterioso. Não somente está a milhares de anos-luz de distância, mas está também escondido sob grande quantidade de poeira de modo que a maior parte das estrelas em seu interior são invisíveis. Pesquisadores de Harvard, estão propondo uma nova maneira de limpar a neblina e registrar as estrelas ali escondidas. Eles sugerem observar os comprimentos de onda de rádio provenientes das estrelas supersônicas.
“Existem muitas, nós não sabemos sobre o centro galáctico, e nós queremos aprender muito”, disse o principal autor do estudo Idan Ginsburg do Harvard-Smithsonian Center for Astrophysics (CfA). “Usando essa técnica, nós podemos encontrar estrelas que ninguém observou antes”.
A grande trajetória do centro da nossa galáxia para a Terra é repleta de tanta poeira que até mesmo dos trilhões de fótons de luz visível que veem em nossa direção, somente um fóton atingirá nossos telescópios. Ondas de rádio, de uma diferente parte do espectro eletromagnético, possui energia mais baixa e comprimentos de onda maiores. Elas podem passar pela poeira de forma ilesa.
Very regular high-frequency pulsation modes in young intermediate-mass starsSérgio Sacani
Asteroseismology probes the internal structures of stars by using their natural
pulsation frequencies1. It relies on identifying sequences of pulsation modes that can
be compared with theoretical models, which has been done successfully for many
classes of pulsators, including low-mass solar-type stars2, red giants3, high-mass stars4
and white dwarfs5. However, a large group of pulsating stars of intermediate mass—the
so-called δ Scuti stars—have rich pulsation spectra for which systematic mode
identification has not hitherto been possible6,7. This arises because only a seemingly
random subset of possible modes are excited and because rapid rotation tends to
spoil regular patterns8–10. Here we report the detection of remarkably regular
sequences of high-frequency pulsation modes in 60 intermediate-mass
main-sequence stars, which enables definitive mode identification. The space
motions of some of these stars indicate that they are members of known associations
of young stars, as confirmed by modelling of their pulsation spectra.
The document describes a study that tested the shear strength of clay soil samples from the Rattlesnake Gulf landslide in New York's Tully Valley. The study used an Autoshear device to measure shear stress, vertical displacement, and horizontal load in order to analyze shear strength parameters. The results will help understand what makes the area susceptible to landslides and inform slope stability analysis. A literature review covers concepts of slope stability, shear strength testing, and factors influencing landslides in the Tully Valley region.
This document presents a non-extensive model for the frequency-magnitude distribution of earthquakes based on Tsallis entropy. The model assumes fragments between fault planes play an active role in triggering earthquakes. By applying maximum entropy principle with Tsallis entropy, the model derives an explicit function relating earthquake energy distribution to fragment size distribution. The function describes earthquake energy distributions over a wide range of energies. Analysis of earthquake data from southern Spain shows the model fits the data better than traditional Boltzmann statistics-based models, particularly for smaller magnitudes where other models fail.
Molecular gas clumps_from_the_destruction_of_icy_bodies_in_beta_pictoris_debr...Sérgio Sacani
1) ALMA observations detected carbon monoxide gas orbiting in a debris disk around the young star Beta Pictoris, with a total mass equivalent to 0.0023 times the mass of Earth's Moon.
2) The gas is distributed asymmetrically, with 30% located in a single clump 85 AU from the star. This gas clump is aligned with the orbit of an inner planet in the system.
3) The gas must be continuously replenished, likely from the destruction of icy planetesimals and comets through collisions within the debris disk. The collisions may be enhanced in the gas clump due to resonances with an unseen giant planet or from remnants of a large collision between
Molecular Gas Clumps from the Destruction of Icy Bodies in the β Pictoris Deb...GOASA
1) ALMA observations detected carbon monoxide gas orbiting in a debris disk around the young star Beta Pictoris, with a total mass equivalent to 0.0023 times the mass of Earth's Moon.
2) The gas is distributed asymmetrically, with 30% located in a single clump 85 AU from the star. This gas clump is aligned with the orbit of an inner planet in the system.
3) The gas must be continuously replenished, likely from the destruction of icy planetesimals and comets through collisions within the debris disk. The collisions may be enhanced in the gas clump due to resonances with an unseen giant planet or the remnants of a large collision between
Dynamical instabilities among giant planets are thought to be nearly ubiquitous, and culminate in the ejection of one or more
planets into interstellar space. Here we perform N-body simulations of dynamical instabilities while accounting for torques from
the galactic tidal field. We find that a fraction of planets that would otherwise have been ejected are instead trapped on very wide
orbits analogous to those of Oort cloud comets. The fraction of ejected planets that are trapped ranges from 1-10%, depending
on the initial planetary mass distribution. The local galactic density has a modest effect on the trapping efficiency and the orbital
radii of trapped planets. The majority of Oort cloud planets survive for Gyr timescales. Taking into account the demographics of
exoplanets, we estimate that one in every 200-3000 stars could host an Oort cloud planet. This value is likely an overestimate, as
we do not account for instabilities that take place at early enough times to be affected by their host stars’ birth cluster, or planet
stripping from passing stars. If the Solar System’s dynamical instability happened after birth cluster dissolution, there is a ∼7%
chance that an ice giant was captured in the Sun’s Oort cloud.
On the possibility of through passage of asteroid bodies across the Earth’s a...Sérgio Sacani
We have studied the conditions of through passage of asteroids with diameters 200, 100, and
50 m, consisting of three types of materials – iron, stone, and water ice, across the Earth’s
atmosphere with a minimum trajectory altitude in the range 10–15 km. The conditions of this
passage with a subsequent exit into outer space with the preservation of a substantial fraction
of the initial mass have been found. The results obtained support our idea explaining one of the
long-standing problems of astronomy – the Tunguska phenomenon, which has not received
reasonable and comprehensive interpretations to date. We argue that the Tunguska event was
caused by an iron asteroid body, which passed through the Earth’s atmosphere and continued
to the near-solar orbit.
The document discusses the growing issue of space debris and meteoroids in Earth's orbit. It provides background on where space debris comes from, including derelict spacecraft and rocket parts. Models like ORDEM and MEM are used to track and predict the movement of debris. Mitigation efforts aim to minimize new debris, but the issue continues growing as the amount of objects in space increases each year. Shields help protect satellites from impacts, but more must be done to curb the problem to ensure safe space travel.
The document discusses the origin of the Moon. It provides a brief history of theories on the Moon's origin from ancient myths to modern scientific studies. The modern consensus is that the Moon formed from the debris of a giant impact between the early Earth and a Mars-sized object (giant impact theory). Computer simulations in the 1970s-1980s showed this scenario can explain the Moon's composition and the angular momentum of the Earth-Moon system. The giant impact theory remains the most widely accepted explanation for how the Moon originated.
Micrometeoroid infall onto Saturn’s rings constrains their age to no more tha...Sérgio Sacani
There is ongoing debate as to whether Saturn’s main rings are relatively young or ancient— having been formed
shortly after Saturn or during the Late Heavy Bombardment. The rings are mostly water-ice but are polluted by
non-icy material with a volume fraction ranging from ∼0.1 to 2%. Continuous bombardment by micrometeoroids exogenic to the Saturnian system is a source of this non-icy material. Knowledge of the incoming mass flux
of these pollutants allows estimation of the rings’ exposure time, providing a limit on their age. Here we report
the final measurements by Cassini’s Cosmic Dust Analyzer of the micrometeoroid flux into the Saturnian system.
Several populations are present, but the flux is dominated by low-relative velocity objects such as from the
Kuiper belt. We find a mass flux between 6.9 · 10−17 and 2.7 · 10−16 kg m−2
s
−1 from which we infer a ring exposure time ≲100 to 400 million years in support of recent ring formation scenarios.
predicting the long term solar wind ion-sputtering source at mercuryJay Kim
This document summarizes research predicting the long-term solar wind ion-sputtering source at Mercury using data from the Helios spacecraft. The key points are:
1) Maps of solar wind proton flux onto Mercury's surface were constructed using a magnetosphere model and solar wind conditions estimated from Helios data when it was in Mercury's orbit.
2) Analysis of Helios data in Mercury's orbital range found that solar wind density increases by a factor of 2.3 from aphelion to perihelion, while velocity is independent of distance. IMF Bz is more likely to be strongly southward at perihelion.
3) Model runs used solar wind parameters matching the most probable conditions identified
Constraints on Ceres’ internal structure and evolution from its shape and gra...Sérgio Sacani
Ceres is the largest body in the asteroid belt with a radius of
approximately 470 km. In part due to its large mass, Ceres more closely approaches
hydrostatic equilibrium than major asteroids. Pre-Dawn mission
shape observations of Ceres revealed a shape consistent with a hydrostatic
ellipsoid of revolution. The Dawn spacecraft Framing Camera has been imaging
Ceres since March 2015, which has led to high-resolution shape models
of the dwarf planet, while the gravity field has been globally determined to
a spherical harmonic degree 14 (equivalent to a spatial wavelength of 211 km)
and locally to 18 (a wavelength of 164 km). We use these shape and gravity
models to constrain Ceres’ internal structure. We find a negative correlation
and admittance between topography and gravity at degree 2 and order
2. Low admittances between spherical harmonic degrees 3 and 16 are well
explained by Airy isostatic compensation mechanism. Different models of isostasy
give crustal densities between 1200 and 1400 kg=m3 with our preferred model
This document summarizes an experiment on the formation of impact craters in sand from dropping spherical ball bearings. The researchers measured the diameter of craters formed from ball bearings of varying mass dropped from increasing heights. They found the crater diameter was related to the total energy of the projectile by a power law equation. A second experiment used flour instead of sand to better simulate impacts on the lunar surface, which has a denser layer below the surface. Additional tests varied the impact angle of the ball bearings to determine the effect on crater diameter.
Age of Jupiter inferred from the distinct genetics and formation times of met...Sérgio Sacani
The age of Jupiter, the largest planet in our Solar System, is still
unknown. Gas-giant planet formation likely involved the growth
of large solid cores, followed by the accumulation of gas onto
these cores. Thus, the gas-giant cores must have formed before
dissipation of the solar nebula, which likely occurred within less
than 10 My after Solar System formation. Although such rapid
accretion of the gas-giant cores has successfully been modeled,
until now it has not been possible to date their formation. Here,
using molybdenum and tungsten isotope measurements on iron
meteorites, we demonstrate that meteorites derive from two
genetically distinct nebular reservoirs that coexisted and remained
spatially separated between ∼1My and ∼3–4My after Solar System
formation. The most plausible mechanism for this efficient separation
is the formation of Jupiter, opening a gap in the disk and
preventing the exchange of material between the two reservoirs.
As such, our results indicate that Jupiter’s core grew to ∼20 Earth
masses within <1 My, followed by amore protracted growth to ∼50
Earth masses until at least ∼3–4 My after Solar System formation.
Thus, Jupiter is the oldest planet of the Solar System, and its solid
core formed well before the solar nebula gas dissipated, consistent
with the core accretion model for giant planet formation.
- The document discusses two potential causes of the mass extinction event that wiped out the dinosaurs - massive volcanic activity from the Deccan Traps (in present-day India), and a large asteroid impact in what is now the Gulf of Mexico.
- Through climate and habitat modeling, the researchers found that scenarios involving prolonged global cooling from the asteroid impact led to a substantial reduction in suitable habitats for dinosaurs worldwide.
- In contrast, simulations of Deccan volcanism, even those with major global warming effects from carbon dioxide release, did not produce conditions severe enough to cause a dinosaur extinction.
- The asteroid impact may have been the primary driver of the non-avian dinosaur extinction, though volcanic warming likely reduced
Exocometary gas in_th_hd_181327_debris_ringSérgio Sacani
An increasing number of observations have shown that gaseous debris discs are not an
exception. However, until now we only knew of cases around A stars. Here we present the first
detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with ALMA
observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric
disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with
radiative transfer calculations we study the dust and CO mass distribution. We find the dust is
distributed in a ring with a radius of 86:0 0:4 AU and a radial width of 23:2 1:0 AU. At
this frequency the ring radius is smaller than in the optical, revealing grain size segregation
expected due to radiation pressure. We also report on the detection of low level continuum
emission beyond the main ring out to 200 AU. We model the CO emission in the non-LTE
regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging
between 1:2 10 6 M and 2:9 10 6 M, depending on the gas kinetic temperature and
collisional partners densities. The CO densities and location suggest a secondary origin, i.e.
released from icy planetesimals in the ring. We derive a CO cometary composition that is
consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is
shaping the dust distribution.
This document proposes a new method for rapidly assessing the age of geological units on Mars using measurements of topographic roughness. It hypothesizes that roughness will be correlated with age derived from crater size-frequency distributions, as craters increase surface roughness over time. To test this, the author analyzes topography images and measures roughness from 125 sites across Mars. Age is calculated from crater counts and compared to roughness measurements. Preliminary results show a significant relationship between some roughness measures and age, though there is also variation likely due to crater degradation processes altering roughness without affecting size distributions. If validated, roughness could provide a faster way to assess relative Martian surface ages than traditional crater counting.
The document summarizes research on the origin of lunar concentric craters. The researchers analyzed data from Clementine, SELENE, and LRO to study 58 known concentric craters. They identified three morphological types and found concentric craters have shallower depths and smaller rim heights than fresh simple craters, suggesting impact degradation or uplift. Distribution near mare/highland boundaries and similarities to floor-fractured craters supports igneous intrusion as the most probable formation mechanism, rather than exogenic processes like simultaneous impacts or impact into layered targets.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
The peculiar shapes of Saturn’s small inner moons as evidence of mergers of s...Sérgio Sacani
The Cassini spacecraft revealed the spectacular, highly irregular
shapes of the small inner moons of Saturn1
, ranging from
the unique 'ravioli-like' forms of Pan and Atlas2,3
to the highly
elongated structure of Prometheus. Closest to Saturn, these
bodies provide important clues regarding the formation process
of small moons in close orbits around their host planet4,
but their range of irregular shapes has not been explained yet.
Here, we show that the spectrum of shapes among Saturn’s
small moons is a natural outcome of merging collisions among
similar-sized moonlets possessing physical properties and
orbits that are consistent with those of the current moons.
A significant fraction of such merging collisions take place
either at the first encounter or after 1–2 hit-and-run events,
with impact velocities in the range of 1–5 times the mutual
escape velocity. Close to head-on mergers result in flattened
objects with large equatorial ridges, as observed on Atlas and
Pan. With slightly more oblique impact angles, collisions lead
to elongated, Prometheus-like shapes. These results suggest
that the current forms of the small moons provide direct
evidence of the processes at the final stages of their formation,
involving pairwise encounters of moonlets of comparable
size4–6. Finally, we show that this mechanism may also
explain the formation of Iapetus’ equatorial ridge7
, as well as
its oblate shape8.
This document presents evidence that massive galaxies at redshift 2.2 (~3 billion years after the Big Bang) undergo an "inside-out quenching" process, where star formation is quenched first in the inner regions and later in the outer disks. High-resolution observations of 22 star-forming galaxies show that the most massive galaxies already have dense bulges similar to local spheroids, while still actively forming stars in their outer disks. The data suggests star formation is suppressed from the inside out on timescales of less than 1 Gyr in the centers and up to a few Gyr in the outer disks, as an "inside-out quenching wave" propagates through the galaxies. This provides insights into how
- The document investigates the implications of a proposed metallicity-dependent initial mass function (IMF), which suggests the IMF varies based on the metallicity of a star formation environment.
- Using observations of globular cluster Palomar 14 and open cluster M42, the author constrains an upper bound for metallicity dependence, resulting in a two-part power law IMF function that depends on metallicity.
- However, the document concludes that current evidence is inadequate to prove a metallicity-dependent IMF, as measurements of cluster IMFs are complicated by issues like dynamics, binaries, and evolution over time.
Evidence for a_complex_enrichment_history_of_the_stream_from_fairall_9_sightlineSérgio Sacani
This study analyzes absorption spectra of the Magellanic Stream (MS) toward the quasar Fairall 9, obtained using the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) and the Very Large Telescope Ultraviolet and Visible Echelle Spectrograph (VLT/UVES). The spectra reveal absorption from multiple velocity components of the MS, indicating multiphase gas. Surprisingly, the sulfur abundance is found to be high ([S/H] = -0.30), five times higher than other MS sightlines, while the nitrogen abundance is lower ([N/H] = -1.15). This points to a complex enrichment history, where the gas toward Fair
Similar to Heterogeneous delivery of silicate and metal to the Earth by large planetesimals (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.