LCROSS was a NASA impactor mission that launched in June 2009 with the goal of determining if water ice exists on the Moon. It consisted of a spent rocket stage that impacted a permanently shadowed crater at the Moon's south pole in October 2009, followed by the LCROSS spacecraft itself impacting 4 minutes later to observe the ejecta plume. The impacts excavated over 200 tons of lunar material and LCROSS's instruments detected evidence of water ice in the plume, confirming its presence on the Moon.
The document summarizes key information about the atmospheres of Venus, Earth, and Mars:
- Venus has a dense, 96% carbon dioxide atmosphere with a surface pressure of 90 bars and average temperature of 850°F, caused by a runaway greenhouse effect. Its clouds are composed of sulfuric acid.
- Earth has an atmosphere composed primarily of nitrogen and oxygen with a pressure of 1 bar and average temperature of 59°F. It hosts water clouds.
- Mars has a thin, 95% carbon dioxide atmosphere with a surface pressure of 0.007 bars and average temperature of -67°F, caused by a runaway refrigerator effect that stripped it of gases over time. It can host clouds of
Spectral gamma logs record radiation from potassium, thorium, and uranium, which can be used to evaluate clay content and type as well as source rock potential. Diffused gamma-ray logs use a gamma source and two detectors to measure photoelectric absorption and Compton scattering, related to lithology and bulk density. Open-hole logging performs measurements in uncased wells while cased-hole logging obtains data through the well casing.
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.
A possible carbonrich_interior_in_superearth_55_cancrieSérgio Sacani
1) The document analyzes the possibility that the interior of the super-Earth exoplanet 55 Cancri e could be carbon-rich rather than oxygen-rich.
2) Models that assume an oxygen-rich interior with iron, silicates, and a water envelope cannot fully explain 55 Cancri e's mass and radius measurements. However, a carbon-rich interior containing iron, silicon carbide, and/or carbon could explain the observations without needing a volatile envelope.
3) A carbon-rich interior for 55 Cancri e is plausible given the reported carbon-rich composition of its host star, though more data is needed on the star's elemental abundances and the planet's atmosphere.
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
LCROSS was a NASA impactor mission that launched in June 2009 with the goal of determining if water ice exists on the Moon. It consisted of a spent rocket stage that impacted a permanently shadowed crater at the Moon's south pole in October 2009, followed by the LCROSS spacecraft itself impacting 4 minutes later to observe the ejecta plume. The impacts excavated over 200 tons of lunar material and LCROSS's instruments detected evidence of water ice in the plume, confirming its presence on the Moon.
The document summarizes key information about the atmospheres of Venus, Earth, and Mars:
- Venus has a dense, 96% carbon dioxide atmosphere with a surface pressure of 90 bars and average temperature of 850°F, caused by a runaway greenhouse effect. Its clouds are composed of sulfuric acid.
- Earth has an atmosphere composed primarily of nitrogen and oxygen with a pressure of 1 bar and average temperature of 59°F. It hosts water clouds.
- Mars has a thin, 95% carbon dioxide atmosphere with a surface pressure of 0.007 bars and average temperature of -67°F, caused by a runaway refrigerator effect that stripped it of gases over time. It can host clouds of
Spectral gamma logs record radiation from potassium, thorium, and uranium, which can be used to evaluate clay content and type as well as source rock potential. Diffused gamma-ray logs use a gamma source and two detectors to measure photoelectric absorption and Compton scattering, related to lithology and bulk density. Open-hole logging performs measurements in uncased wells while cased-hole logging obtains data through the well casing.
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.
A possible carbonrich_interior_in_superearth_55_cancrieSérgio Sacani
1) The document analyzes the possibility that the interior of the super-Earth exoplanet 55 Cancri e could be carbon-rich rather than oxygen-rich.
2) Models that assume an oxygen-rich interior with iron, silicates, and a water envelope cannot fully explain 55 Cancri e's mass and radius measurements. However, a carbon-rich interior containing iron, silicon carbide, and/or carbon could explain the observations without needing a volatile envelope.
3) A carbon-rich interior for 55 Cancri e is plausible given the reported carbon-rich composition of its host star, though more data is needed on the star's elemental abundances and the planet's atmosphere.
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
The EPOXI flyby of comet Hartley 2 revealed several new results about the comet's activity, grains, and nucleus. Much of Hartley 2's water comes from icy grains moving tailward, which sublime slowly. The two ends of the comet have very different CO2 abundances, and CO abundance was found to be much lower than expected. The nucleus appears to have ice on its surface and heterogeneous thermal properties. Every cometary encounter continues to surprise scientists with new phenomena and processes that demonstrate comets' diversity.
The international Cassini-Huygens spacecraft was launched on October 15, 1997 and had a marathon 7-year 2-billion mile journey to the distant planet Saturn. The 23-foot tall, 14-foot wide, 6-ton spacecraft is the largest most sophisticated outer planet spacecraft ever built, and is in its third year of operation in orbit around the planet Saturn. Cassini-Huygens has been returning extraordinary data about the entire Saturn system: the spectacular rings; the numerous icy satellites with a variety of unique surface features; the giant planet itself; a huge magneto-sphere teeming with particles that interact with the rings and moons; and the intriguing moon Titan, which is slightly larger than the planet Mercury, and whose hazy atmosphere is denser than that of Earth. This talk will be an overview of the Cassini-Huygens mission to Saturn with a summary of the top science returns of its first three years in orbit.
The Minnesota Space Grant Consortium, run out of the Department of Aerospace Engineering and Mechanics at the University of Minnesota, hosts Trina Ray of NASA JPL on January 22, 2008.
This document summarizes a study on the formation of polar ring galaxies through two proposed scenarios: the merging scenario and the accretion scenario. The merging scenario involves a head-on collision between two galaxies, where one becomes the host galaxy and the other's gas forms the polar ring. The accretion scenario involves tidal interactions that allow gas from one galaxy to be accreted by another galaxy to form a polar ring. Through simulations, the study finds that both scenarios can produce stable polar rings, but that the accretion scenario better matches observed properties of polar ring galaxies, such as the frequency and morphology of the rings. The study concludes the accretion scenario is both more likely and more supported by observations to explain how most polar ring galaxies form.
This document summarizes information about the solar system and beyond. It discusses the reclassification of Pluto as a dwarf planet in 2006 based on its size and inability to clear its orbital neighborhood. It also describes the discovery of new moons around Pluto in 2005 and 2006. The document discusses other large trans-Neptunian objects like Eris, Sedna, and Quaoar. It provides information on comets, asteroids, meteoroids, and meteorites. It discusses theories on the origin of comets from the Oort cloud and Kuiper belt and describes comet tails and nucleus. The document summarizes crater formation from meteorite impacts and mass extinction events. It also discusses finding exoplanets using the radial velocity
Small dust particles escaping from Pluto's moons Nix and Hydra could temporarily form a ring around Pluto due to impacts, but the solar radiation pressure would remove about half of 1 micrometer particles within a year by causing collisions with Pluto and its moons. Numerical simulations found that a tenuous ring with an optical depth of 6×10^-11 could be maintained by dust released from Nix and Hydra.
Cassini has been orbiting Saturn since 2004, conducting numerous science investigations of the planet, its rings and moons. It discovered water plumes erupting from Enceladus, signs of possible oceans and organic activity on Titan, and continues monitoring Saturn's weather, rings and developing new insights into the moons. Cassini remains in excellent health and its Solstice mission extends through 2017, promising more discoveries to come from this unprecedented exploration of the Saturn system.
Beyond the Kuiper Belt Edge: New High Perihelion Trans-Neptunian Objects With...Sérgio Sacani
We are conducting a survey for distant solar system objects beyond the Kuiper
Belt edge ( 50 AU) with new wide-field cameras on the Subaru and CTIO tele-
scopes. We are interested in the orbits of objects that are decoupled from the
giant planet region in order to understand the structure of the outer solar sys-
tem, including whether a massive planet exists beyond a few hundred AU as first
reported in Trujillo and Sheppard (2014). In addition to discovering extreme
trans-Neptunian objects detailed elsewhere, we have found several objects with
high perihelia (q > 40 AU) that differ from the extreme and inner Oort cloud
objects due to their moderate semi-major axes (50 < a < 100 AU) and eccen-
tricities (e . 0.3). Newly discovered objects 2014 FZ71 and 2015 FJ345 have
the third and fourth highest perihelia known after Sedna and 2012 VP113, yet
their orbits are not nearly as eccentric or distant. We found several of these high
perihelion but moderate orbit objects and observe that they are mostly near Nep-
tune mean motion resonances and have significant inclinations (i > 20 degrees).
These moderate objects likely obtained their unusual orbits through combined
interactions with Neptune’s mean motion resonances and the Kozai resonance,
similar to the origin scenarios for 2004 XR190. We also find the distant 2008
ST291 has likely been modified by the MMR+KR mechanism through the 6:1
Neptune resonance. We discuss these moderately eccentric, distant objects along
with some other interesting low inclination outer classical belt objects like 2012
FH84 discovered in our ongoing survey.
Modeling extrasolar planetary atmospheres discusses techniques for modeling exoplanet atmospheres including:
1) 1D radiative models that reconstruct atmospheric temperature structures and simulate thermal emission and reflected light.
2) 2D and 3D global circulation models that simulate atmospheric winds and temperature distributions driven by stellar irradiation and planetary rotation.
3) Advanced 3D models that combine radiative transfer with hydrodynamics to model atmospheric chemistry, clouds, and winds. These simulations produce synthetic spectra and light curves for comparison to observations.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
The exceptional soft_x_ray_halo_of_the_galaxy_merger_ngc6240Sérgio Sacani
The document summarizes a recent 150-ks Chandra observation of the galaxy merger NGC 6240. Extended soft X-ray emission is detected over a 110x80 kpc region around NGC 6240. Spectral analysis finds the emission comes from hot gas with a temperature of around 7.5 million K and a total mass of about 10^10 solar masses. The gas properties suggest widespread star formation over the past 200 Myr rather than a recent nuclear starburst. The fate of the diffuse hot gas after the galaxy merger is uncertain but it may be retained and evolve into the halo of an elliptical galaxy.
Stable isotopes can be used as tracers to study biological, geological, and environmental processes because different isotopes of the same element fractionate or separate from each other during physical, chemical, and biological reactions due to differences in mass. Fractionation leads to geographic variations in stable isotope ratios that provide insight into past climate conditions, biological activity, and biogeochemical cycling. Stable isotope analysis is a valuable tool for paleoclimate reconstruction, sedimentary provenance, and understanding the evolution of early life on Earth.
Grb 130606a as_a_probe_of_the_intergalactic_medium_and_the_interstelar_medium...Sérgio Sacani
This document summarizes observations of the gamma-ray burst GRB 130606A at a redshift of z=5.913 using spectroscopy from the MMT and Gemini telescopes. The high quality spectra exhibit a smooth near-infrared continuum that is sharply cut off by Lyman-alpha absorption at z=5.91, with some flux transmitted through the Lyman-alpha forest at lower redshifts. Metal absorption lines in the host galaxy are used to constrain its metallicity between -1.7 and -0.5 solar. Transmission in the Lyman-alpha forest is found to evolve consistently with previous quasar observations. An extended region at z=5.77 shows no Lyman-alpha transmission,
What determines the_density_structure_of_molecular_cloudsSérgio Sacani
This document analyzes column density probability distribution functions (PDFs) derived from Herschel observations of the Orion B, Aquila, and Polaris molecular clouds to understand what physical processes influence the density structure. The PDFs of Orion B and Aquila show a lognormal distribution at low densities transitioning to a power-law tail at high densities, indicating gravitational collapse. The Orion B PDF is broader, likely due to external compression. The quiescent Polaris subregion PDF is nearly lognormal, suggesting turbulence governs its density, while a filament subregion shows excess density above a visual extinction of 1, possibly from physical processes like magnetic fields. The document concludes that turbulence, gravity, collapse, and external compression
The document discusses high energy astrophysical research conducted at the Maidanak Observatory in Uzbekistan. It provides historical context about the transfer of Islamic science to the region in the 11th century. It then describes the observatory's facilities, including its six telescopes and five CCD cameras. The main fields of scientific research at the observatory are also listed, such as gravitational lensing systems, active galactic nuclei, gamma-ray bursts, and blazars. Specific research on gravitational lensing systems and blazars using data from Maidanak is summarized.
The document discusses scientific evidence that supports the propositions in the Quran that the sun moves and the earth is motionless:
1) Satellite observations show the earth is slightly oval and lacks shock waves, indicating it does not rotate or revolve at high speeds.
2) The "geodetic wrap" effect and experiments with the "trigger effect" technology prove the earth is motionless at the center of the universe.
3) Experiments controlling the magnetic field with Helmholtz coils show Earth's magnetic field is stable, indicating it is not subject to major changes from earth's movement.
4) Michelson-Morley experiments found no difference in the speed of light in different directions, proving
The magma ocean stage in the formation of rocky-terrestrial planetsAdvanced-Concepts-Team
1) The document discusses the magma ocean stage in the early formation of rocky terrestrial planets like Earth. A magma ocean is a liquid layer at the surface after giant impacts melt the mantle.
2) Energy input from impacts and radioactive decay in the early solar system led to magma oceans. The talk analyzes how atmospheric thermal blanketing could prolong the magma ocean stage for millions of years.
3) The model results show that on Earth, the magma ocean likely lasted a few million years. During this stage, CO2 degassed from the interior early while H2O degassed later, and the atmosphere switched from being CO2-dominated to H2O-dominated over
A Subsurface Magma Ocean on Io: Exploring the Steady State of Partially Molte...Sérgio Sacani
Intense tidal heating within Io produces active volcanism on the surface, and its internal structure has long been a
subject of debate. A recent reanalysis of the Galileo magnetometer data suggested the presence of a high-meltfraction layer with >50 km thickness in the subsurface region of Io. Whether this layer is a “magmatic sponge”
with interconnected solid or a rheologically liquid “magma ocean” would alter the distribution of tidal heating
and would also influence the interpretation of various observations. To this end, we explore the steady state of a
magmatic sponge and estimate the amount of internal heating necessary to sustain such a layer with a high
degree of melting. Our results show that the rate of tidal dissipation within Io is insufficient to sustain a partialmelt layer of f > 0.2 for a wide range of parameters, suggesting that such a layer would swiftly separate into two
phases. Unless melt and/or solid viscosities are at the higher end of the estimated range, a magmatic sponge
would be unstable, and thus a high-melt-fraction layer suggested in Khurana et al. is likely to be a subsurface
magma ocean.
The EPOXI flyby of comet Hartley 2 revealed several new results about the comet's activity, grains, and nucleus. Much of Hartley 2's water comes from icy grains moving tailward, which sublime slowly. The two ends of the comet have very different CO2 abundances, and CO abundance was found to be much lower than expected. The nucleus appears to have ice on its surface and heterogeneous thermal properties. Every cometary encounter continues to surprise scientists with new phenomena and processes that demonstrate comets' diversity.
The international Cassini-Huygens spacecraft was launched on October 15, 1997 and had a marathon 7-year 2-billion mile journey to the distant planet Saturn. The 23-foot tall, 14-foot wide, 6-ton spacecraft is the largest most sophisticated outer planet spacecraft ever built, and is in its third year of operation in orbit around the planet Saturn. Cassini-Huygens has been returning extraordinary data about the entire Saturn system: the spectacular rings; the numerous icy satellites with a variety of unique surface features; the giant planet itself; a huge magneto-sphere teeming with particles that interact with the rings and moons; and the intriguing moon Titan, which is slightly larger than the planet Mercury, and whose hazy atmosphere is denser than that of Earth. This talk will be an overview of the Cassini-Huygens mission to Saturn with a summary of the top science returns of its first three years in orbit.
The Minnesota Space Grant Consortium, run out of the Department of Aerospace Engineering and Mechanics at the University of Minnesota, hosts Trina Ray of NASA JPL on January 22, 2008.
This document summarizes a study on the formation of polar ring galaxies through two proposed scenarios: the merging scenario and the accretion scenario. The merging scenario involves a head-on collision between two galaxies, where one becomes the host galaxy and the other's gas forms the polar ring. The accretion scenario involves tidal interactions that allow gas from one galaxy to be accreted by another galaxy to form a polar ring. Through simulations, the study finds that both scenarios can produce stable polar rings, but that the accretion scenario better matches observed properties of polar ring galaxies, such as the frequency and morphology of the rings. The study concludes the accretion scenario is both more likely and more supported by observations to explain how most polar ring galaxies form.
This document summarizes information about the solar system and beyond. It discusses the reclassification of Pluto as a dwarf planet in 2006 based on its size and inability to clear its orbital neighborhood. It also describes the discovery of new moons around Pluto in 2005 and 2006. The document discusses other large trans-Neptunian objects like Eris, Sedna, and Quaoar. It provides information on comets, asteroids, meteoroids, and meteorites. It discusses theories on the origin of comets from the Oort cloud and Kuiper belt and describes comet tails and nucleus. The document summarizes crater formation from meteorite impacts and mass extinction events. It also discusses finding exoplanets using the radial velocity
Small dust particles escaping from Pluto's moons Nix and Hydra could temporarily form a ring around Pluto due to impacts, but the solar radiation pressure would remove about half of 1 micrometer particles within a year by causing collisions with Pluto and its moons. Numerical simulations found that a tenuous ring with an optical depth of 6×10^-11 could be maintained by dust released from Nix and Hydra.
Cassini has been orbiting Saturn since 2004, conducting numerous science investigations of the planet, its rings and moons. It discovered water plumes erupting from Enceladus, signs of possible oceans and organic activity on Titan, and continues monitoring Saturn's weather, rings and developing new insights into the moons. Cassini remains in excellent health and its Solstice mission extends through 2017, promising more discoveries to come from this unprecedented exploration of the Saturn system.
Beyond the Kuiper Belt Edge: New High Perihelion Trans-Neptunian Objects With...Sérgio Sacani
We are conducting a survey for distant solar system objects beyond the Kuiper
Belt edge ( 50 AU) with new wide-field cameras on the Subaru and CTIO tele-
scopes. We are interested in the orbits of objects that are decoupled from the
giant planet region in order to understand the structure of the outer solar sys-
tem, including whether a massive planet exists beyond a few hundred AU as first
reported in Trujillo and Sheppard (2014). In addition to discovering extreme
trans-Neptunian objects detailed elsewhere, we have found several objects with
high perihelia (q > 40 AU) that differ from the extreme and inner Oort cloud
objects due to their moderate semi-major axes (50 < a < 100 AU) and eccen-
tricities (e . 0.3). Newly discovered objects 2014 FZ71 and 2015 FJ345 have
the third and fourth highest perihelia known after Sedna and 2012 VP113, yet
their orbits are not nearly as eccentric or distant. We found several of these high
perihelion but moderate orbit objects and observe that they are mostly near Nep-
tune mean motion resonances and have significant inclinations (i > 20 degrees).
These moderate objects likely obtained their unusual orbits through combined
interactions with Neptune’s mean motion resonances and the Kozai resonance,
similar to the origin scenarios for 2004 XR190. We also find the distant 2008
ST291 has likely been modified by the MMR+KR mechanism through the 6:1
Neptune resonance. We discuss these moderately eccentric, distant objects along
with some other interesting low inclination outer classical belt objects like 2012
FH84 discovered in our ongoing survey.
Modeling extrasolar planetary atmospheres discusses techniques for modeling exoplanet atmospheres including:
1) 1D radiative models that reconstruct atmospheric temperature structures and simulate thermal emission and reflected light.
2) 2D and 3D global circulation models that simulate atmospheric winds and temperature distributions driven by stellar irradiation and planetary rotation.
3) Advanced 3D models that combine radiative transfer with hydrodynamics to model atmospheric chemistry, clouds, and winds. These simulations produce synthetic spectra and light curves for comparison to observations.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
The exceptional soft_x_ray_halo_of_the_galaxy_merger_ngc6240Sérgio Sacani
The document summarizes a recent 150-ks Chandra observation of the galaxy merger NGC 6240. Extended soft X-ray emission is detected over a 110x80 kpc region around NGC 6240. Spectral analysis finds the emission comes from hot gas with a temperature of around 7.5 million K and a total mass of about 10^10 solar masses. The gas properties suggest widespread star formation over the past 200 Myr rather than a recent nuclear starburst. The fate of the diffuse hot gas after the galaxy merger is uncertain but it may be retained and evolve into the halo of an elliptical galaxy.
Stable isotopes can be used as tracers to study biological, geological, and environmental processes because different isotopes of the same element fractionate or separate from each other during physical, chemical, and biological reactions due to differences in mass. Fractionation leads to geographic variations in stable isotope ratios that provide insight into past climate conditions, biological activity, and biogeochemical cycling. Stable isotope analysis is a valuable tool for paleoclimate reconstruction, sedimentary provenance, and understanding the evolution of early life on Earth.
Grb 130606a as_a_probe_of_the_intergalactic_medium_and_the_interstelar_medium...Sérgio Sacani
This document summarizes observations of the gamma-ray burst GRB 130606A at a redshift of z=5.913 using spectroscopy from the MMT and Gemini telescopes. The high quality spectra exhibit a smooth near-infrared continuum that is sharply cut off by Lyman-alpha absorption at z=5.91, with some flux transmitted through the Lyman-alpha forest at lower redshifts. Metal absorption lines in the host galaxy are used to constrain its metallicity between -1.7 and -0.5 solar. Transmission in the Lyman-alpha forest is found to evolve consistently with previous quasar observations. An extended region at z=5.77 shows no Lyman-alpha transmission,
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This document analyzes column density probability distribution functions (PDFs) derived from Herschel observations of the Orion B, Aquila, and Polaris molecular clouds to understand what physical processes influence the density structure. The PDFs of Orion B and Aquila show a lognormal distribution at low densities transitioning to a power-law tail at high densities, indicating gravitational collapse. The Orion B PDF is broader, likely due to external compression. The quiescent Polaris subregion PDF is nearly lognormal, suggesting turbulence governs its density, while a filament subregion shows excess density above a visual extinction of 1, possibly from physical processes like magnetic fields. The document concludes that turbulence, gravity, collapse, and external compression
The document discusses high energy astrophysical research conducted at the Maidanak Observatory in Uzbekistan. It provides historical context about the transfer of Islamic science to the region in the 11th century. It then describes the observatory's facilities, including its six telescopes and five CCD cameras. The main fields of scientific research at the observatory are also listed, such as gravitational lensing systems, active galactic nuclei, gamma-ray bursts, and blazars. Specific research on gravitational lensing systems and blazars using data from Maidanak is summarized.
The document discusses scientific evidence that supports the propositions in the Quran that the sun moves and the earth is motionless:
1) Satellite observations show the earth is slightly oval and lacks shock waves, indicating it does not rotate or revolve at high speeds.
2) The "geodetic wrap" effect and experiments with the "trigger effect" technology prove the earth is motionless at the center of the universe.
3) Experiments controlling the magnetic field with Helmholtz coils show Earth's magnetic field is stable, indicating it is not subject to major changes from earth's movement.
4) Michelson-Morley experiments found no difference in the speed of light in different directions, proving
The magma ocean stage in the formation of rocky-terrestrial planetsAdvanced-Concepts-Team
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2) Energy input from impacts and radioactive decay in the early solar system led to magma oceans. The talk analyzes how atmospheric thermal blanketing could prolong the magma ocean stage for millions of years.
3) The model results show that on Earth, the magma ocean likely lasted a few million years. During this stage, CO2 degassed from the interior early while H2O degassed later, and the atmosphere switched from being CO2-dominated to H2O-dominated over
A Subsurface Magma Ocean on Io: Exploring the Steady State of Partially Molte...Sérgio Sacani
Intense tidal heating within Io produces active volcanism on the surface, and its internal structure has long been a
subject of debate. A recent reanalysis of the Galileo magnetometer data suggested the presence of a high-meltfraction layer with >50 km thickness in the subsurface region of Io. Whether this layer is a “magmatic sponge”
with interconnected solid or a rheologically liquid “magma ocean” would alter the distribution of tidal heating
and would also influence the interpretation of various observations. To this end, we explore the steady state of a
magmatic sponge and estimate the amount of internal heating necessary to sustain such a layer with a high
degree of melting. Our results show that the rate of tidal dissipation within Io is insufficient to sustain a partialmelt layer of f > 0.2 for a wide range of parameters, suggesting that such a layer would swiftly separate into two
phases. Unless melt and/or solid viscosities are at the higher end of the estimated range, a magmatic sponge
would be unstable, and thus a high-melt-fraction layer suggested in Khurana et al. is likely to be a subsurface
magma ocean.
Still the Biggest Control Knob: Carbon Dioxide in Earth's Climate "History"SERC at Carleton College
Carbon dioxide has been the primary driver of temperature changes throughout Earth's climate history. Three key points:
1) Changes in CO2 levels strongly correlate with temperature changes over both short and long time periods in the past. Nothing else can explain most features of climate history as well as the role of CO2.
2) The physical properties of CO2 and its role as a greenhouse gas are well established and have been confirmed by observations of Earth and other planets. CO2 is able to warm the planet due to its absorption of infrared radiation.
3) A rock weathering feedback loop has acted over long time scales to regulate Earth's temperature by sequestering more CO2 in rocks during warm periods and
The document discusses the formation of the solar system from a molecular cloud. It describes how:
1) The cloud collapsed due to gravity, forming a hot solar nebula with a temperature gradient.
2) Atoms condensed into microscopic particles in different regions based on temperature, then accreted into planetesimals.
3) Terrestrial planetesimals grew into protoplanets through collisions, then differentiated into cores and mantles.
4) Jovian protoplanets captured gas and ice from the nebula through gravitational collapse, forming large atmospheres.
Paleoclimatology is the study of past climates through the use of proxies such as microbial life found in sediment cores, ice cores, and tree rings. Researchers use various analytical methods to extract information from these proxies about past climate conditions. For example, oxygen isotope ratios in foraminifera and diatom shells can provide information about past water temperatures, and the abundance and composition of microbial populations may indicate environmental conditions like temperature. Volcanic eruptions can influence climate in both the short and long term. Large eruptions that eject ash and sulfur dioxide into the stratosphere can block sunlight and cool the planet for several years through radiation scattering. However, massive eruptions that release large amounts of carbon dioxide may
1. The formation and evolution of the Solar System began about 4.57 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center to form the Sun, while the rest flattened into a protoplanetary disk from which the planets, moons, asteroids and other small bodies formed.
2. According to the nebular hypothesis, Earth formed about 4.54 billion years ago from accretion of planetary material in the solar nebula. Within the first 100-200 million years, early Earth had formed extensive oceans and seas.
3. Key events in the development of early Earth included the formation of its layered internal structure through the sinking of
Origin and interiors of the earth LECTURE OF CIVIL ENGINEERING DRAWINGSafiullah Khan
This document provides an overview of engineering geology and the interior structure of Earth. It discusses:
- Engineering geology as the application of geology to civil engineering projects.
- The interior structure of Earth, including the crust, mantle (with upper, lower, and outer layers), liquid outer core, and solid inner core.
- Theories for the origin of Earth, including the nebular hypothesis of Kant and Laplace where Earth formed from a contracting gas cloud/nebula around the sun.
The document outlines the 4 step process of planetary formation:
1) Collision and accretion of cm-sized particles into km-sized objects
2) Physical collisions of km-sized objects forming 10-100 km objects
3) Gravitational accretion sweeping up smaller bodies to form protoplanets
4) Heating and impacts forming molten protoplanets that differentiate into layers.
1) The document discusses a proposed method for maintaining a formation of millions of small spacecraft called "flyers" in orbit around the Earth-Sun L1 point to form a solar shield to counteract global warming.
2) Each flyer would be about 1 meter in diameter and 1 gram in mass, and they would be launched in stacks of 800,000 flyers weighing 1 ton total.
3) Maintaining the formation would rely on randomizing the initial velocities of flyers and using their solar sailing capabilities and differences in solar pressure to keep them separated in halo-like trajectories without using propellant. Failed or malfunctioning flyers could be disposed of without threatening other spacecraft.
This document discusses colonization of Mars and terraforming the planet. It outlines the need for colonization, including population growth and making humans a multiplanetary species. Mars is a potential target for colonization due to its proximity and similarities to Earth. However, living on Mars presents challenges like low temperatures, thin atmosphere, and high radiation. The document proposes methods for terraforming Mars, including using orbital mirrors to increase sunlight and warming, importing ammonia-rich asteroids to add greenhouse gases, and producing halocarbon gases. Each method aims to make Mars' environment more hospitable for human life.
1) Global climate models that include sophisticated cloud schemes show that tidally locked planets can develop thick water clouds near the substellar point due to strong convection. These clouds greatly increase the planetary albedo and stabilize temperatures, allowing habitability at twice the stellar flux previously thought possible.
2) The cloud feedback is stabilizing, as higher stellar flux produces stronger convection and higher albedos. Substellar clouds can block outgoing radiation, reducing the day-night temperature contrast.
3) Non-tidally locked planets do not experience this stabilizing cloud feedback, as clouds only form over parts of the tropics and mid-latitudes. Their albedo decreases with increasing stellar flux, producing a destabil
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2) The formulas relate to the effect of gravity on light speed, the Earth's magnetism, and calculations of years in the past.
3) Evidence proposed to support the formulas includes the gravitational red-shift effect on light and observations from satellite imaging and interferometry.
Still the Biggest Control Knob: Carbon Dioxide in Earth’s Climate HistorySERC at Carleton College
This document summarizes a presentation by Richard Alley on factors that control Earth's climate and temperature. It finds that changes in carbon dioxide levels have been the primary driver of climate changes in Earth's history based on several lines of evidence: correlations between CO2 and temperature in the geological record; the physical properties of CO2 as a greenhouse gas; and CO2 providing the best explanation for major climate shifts like Snowball Earth periods and warm periods when the sun was less bright. The presentation discusses how CO2 levels are regulated by geological processes like volcanism and rock weathering over long time scales. It also reviews evidence of very high CO2 levels during past warm periods like the Paleocene-Eocene Thermal Maximum.
Artigo mostra resultados obtidos com o OSIRIS que mostra manchas brilhantes na superfície do cometa 67P/Churyumov-Gerasimenko, interpretadas como sendo gelo de água e provadas via experimentos de laboratório.
3d modeling of_gj1214b_atmosphere_formation_of_inhomogeneous_high_cloouds_and...Sérgio Sacani
Uma equipe de cientistas da Universidade de Washington e da Universidade de Toronto foram os primeiros a simular nuvens exóticas em 3D na atmosfera de um exoplaneta.
O objeto em questão, é o GJ 1214b, um exoplaneta chamado de mini-Netuno que foi descoberto, seis anos atrás pelos astrônomos no Harvard-Smithsonian Center for Astrophysics.
Também conhecido como Gliese 1214b, esse mundo tem cerca de 2.7 vezes o diâmetro da Terra e uma massa quase 7 vezes maior que a massa do nosso planeta. Ele está localizado a cerca de 52 anos-luz de distância na constelação de Ophiuchus.
O planeta orbita a estrela anã vermelha, GJ 1214, a cada 38 horas, a uma distância de 1.3 milhões de milhas.
De acordo com estudos prévios, o planeta tem uma atmosfera rica em água ou hidrogênio com extensas nuvens.
“Deve existir altas nuvens ou uma névoa orgânica na atmosfera – como nós observamos em Titã. Sua temperatura atmosférica excede o ponto de fusão da água”, disse o Dr. Benjamin Charnay, um dos membros da equipe da Universidade de Washington.
Jack Oughton - Galaxy Formation Journal 02.docxJack Oughton
This document discusses theories of galaxy formation from the early universe following the Big Bang. It describes how small fluctuations in the initially uniform hydrogen/helium gas may have led to denser regions that accreted more mass over time through either a "top-down" or "bottom-up" process. The bottom-up theory, in which smaller clumps merged into larger structures, best matches current observational evidence of hierarchical galaxy clustering. However, fully explaining galaxy formation remains challenging due to uncertainties around gas dynamics and dark matter.
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Geology is the study of the Earth, including its composition, structure, physical properties, history, and the processes that act on it. The Earth formed around 4.5 billion years ago from the solar nebula. It differentiated into a solid crust and mantle, and a liquid outer core and solid inner core due to gravity and radioactive heating. The Earth has since undergone significant internal and external changes. The atmosphere formed from gases released from volcanoes, and the oceans formed as water accumulated on the cooling surface. Life emerged on Earth around 3.5 billion years ago. The lithosphere is divided into tectonic plates that move over the mantle due to convection currents in the upper mantle. The biosphere interacts with and alters
The document provides information about geology and the structure of the Earth. It discusses the following key points:
1. Geology is the study of the Earth, including its chemical and physical properties, formation processes, and changes from creation to present day.
2. The Earth is composed of several layers including the crust, mantle, outer core, and inner core. The crust and upper mantle make up the lithosphere which is divided into tectonic plates.
3. The formation of the Earth and solar system is explained by several hypotheses including the nebular hypothesis which postulates that the Earth formed from a contracting cloud of gas and dust around the sun.
This document summarizes igneous petrology and the structure and composition of the Earth's interior. It discusses how the Earth is composed of layers including the crust, mantle, outer core, and inner core. The crust is divided into oceanic and continental crust. The mantle makes up most of the Earth's volume and is composed of ultramafic rock. Heat transfer mechanisms like conduction, convection, and advection are described. The geothermal gradient and how temperature increases with depth is also summarized. Plate tectonics and mantle convection are driving the dynamic cooling of the Earth.
Similar to N.20 capria main-belt-comets-a-new-class-of-objects (20)
How to Add Chatter in the odoo 17 ERP ModuleCeline George
In Odoo, the chatter is like a chat tool that helps you work together on records. You can leave notes and track things, making it easier to talk with your team and partners. Inside chatter, all communication history, activity, and changes will be displayed.
The simplified electron and muon model, Oscillating Spacetime: The Foundation...RitikBhardwaj56
Discover the Simplified Electron and Muon Model: A New Wave-Based Approach to Understanding Particles delves into a groundbreaking theory that presents electrons and muons as rotating soliton waves within oscillating spacetime. Geared towards students, researchers, and science buffs, this book breaks down complex ideas into simple explanations. It covers topics such as electron waves, temporal dynamics, and the implications of this model on particle physics. With clear illustrations and easy-to-follow explanations, readers will gain a new outlook on the universe's fundamental nature.
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
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LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
Executive Directors Chat Leveraging AI for Diversity, Equity, and InclusionTechSoup
Let’s explore the intersection of technology and equity in the final session of our DEI series. Discover how AI tools, like ChatGPT, can be used to support and enhance your nonprofit's DEI initiatives. Participants will gain insights into practical AI applications and get tips for leveraging technology to advance their DEI goals.
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
1. MAIN BELT COMETS
A new class of objects
Maria Teresa Capria, Simone Marchi, Maria
Cristina De Sanctis, Angioletta Coradini and
Eleonora Ammannito
International Workshop on Paolo Farinella, Università di Pisa, June 14-16, 2010
2. A new class of objects
Main belt comets are objects orbiting in the Main Belt,
showing cometary activity, with Tj>3
name a (AU) e i Tj q (AU) d (km)
133P/Elst-Pizarro 3.164 0.153 1.38 3.184 2.636 4.6
P/2005 U1 Read 3.165 0.253 1.267 3.153 2.365 <0.6
176P/LINEAR 3.218 0.144 1.40 3.166 2.581 4.8
P/2008 R1 (Garradd) 2.726 0.342 15.9 3.216 1.793 <1.4
Jewitt et al., 2008; 2009
Dynamical transition from outer Solar System is Hsieh et al., 2009
nowadays considered almost impossible, and their
orbits are stable: they formed in in place, or are
there since a lot of time .
Orbital elements point to Themis family.
Infrared spectroscopy shows ice widespread on
the surface of 24 Themis (Campins et al. ,2010).
3. A new class of objects
4 objects known imply
many more currently
active, and a greater
number currently
inactive
It has been suggested
that the observed
activity could have
been triggered by
impacts.
Jewitt, 2008
They could be the third known comet source.
They are potential contributor to Earth oceans.
4. Crater formation rate in the Main Belt
Which is now the crater formation rate in the Main Asteroid
Belt (2. – 3.27 AU)?
The range of interest is 0.1 – 1 km, because MBCs are small
and we are not looking for fragmentations.
The method is based on the dynamical model by Bottke et al. (2002;
2005). First the flux of impactors is derived: we consider the average Main
Belt impact rate and impact velocity.
Impacts are converted into craters using an appropriate scaling law
from hydrocode simulations (Nolan et al .1996).
Then we compute the cumulative distribution of expected crater
diameters.
Marchi et al, 2005; 2009
5. Crater formation rate in the Main Belt
The average time of formation of a crater in the size-range
from 0.1 to 1 km is:
133P/Elst- one crater per 0.9 Myr
Pizarro
P/2005 U1 one crater per 54 Myr
differences in the
Read
time scale are
176P/LINEAR one crater per 0.8 Myr solely due to
P/2008 R1 one crater per 10 Myr differences in the
(Garradd) size of the bodies
6. Thermal modeling
We are assuming that a MBC is a comet-like body: a porous
intimate mixture of water ice and refractary particles.
We are assuming that an impact has recently
happened, triggering a more or less stable
cometary activity.
We run thermal models to simulate this kind of activity
and study possibility and duration of an active phase.
7. Thermal modeling
The nucleus model is composed by a Rome model
porous mixture of ices and a Capria et al., 2000; 2005; 2009
refractory component (spherical De Sanctis et al., 2003;2005;2008.,
grains distributed in different size
classes).
The numerical code is solving heat
and gas diffusion equations, Due to the rising temperature, ices
computings how the heat diffuses start to sublimate, and the nucleus
in the porous cometary material, differentiates giving rise to a
inducing the sublimation- layered structure, in which the
recondensation of water and boundary between different layers is
volatiles. a sublimation front.
The temperature on the surface is When the ices begin to sublimate
obtained by a balance between the the dust particles become free and
solar input and the energy re- can undergo the drag exerted by the
emitted in the infrared, conducted escaping gas, so that they move
in the interior and used to sublimate toward the surface and can be blown
surface ices. off or accumulate to form a crust.
8. A model comet: P/2005 U1 Read
Input parameters P/2005 U1
Read
a 3.165
e 0.253
Diameter (m) 600
Dust/ice 3
Meech and Svoren, 2005
Rotation period (h) 10
Average density 586
(kg/m3)
9. A model comet: P/2005 U1 Read
Exposed ice
Gas flux
equator
85°
30°
10. A model comet: P/2005 U1 Read Exposed ice
Dust flux
Erosion per orbit
at equator is >2
m in 10 years.
Stratigraphy
30°
equator
85°
11. A model comet: P/2005 U1 Read Buried ice
An impact could trigger some activity even without exposing
fresh ice, but simply bringing the heat wave closer to an ice-rich
layer. Ice can sublimate under a porous mantle.
We are assuming that an impact has recently happened and that
an ice-rich layer has been brought closer to the surface. The surface
is still covered by a devolatilized, porous mantle.
We ran models with different mantle thickness and properties, to
determine possibility and duration of an active phase.
Two kind of dust particles (and mantles): silicatic and silicatic/CHON
McDonnell et al.1991
12. A model comet: P/2005 U1 Read Buried ice
Gas flux
Silicatic mantle (0.1 m and 0.5 m)
Silicatic/CHON mantle (0.1 m and 0.5 m)
13. A model comet: P/2005 U1 Read Buried ice
Silicatic mantle 0.1 m thick: the sublimation front recedes 0.15 m in 1000 years
Temperature under the mantle: 162 K
Silicatic mantle 0.5 m thick: no changes in 1000 years
Temperature under the mantle: 155 K
Organic mantle 0.1 m thick: the sublimation front recedes 0.05 m in 1000 years
Temperature under the mantle: 162 K
Organic mantle 0.5 m thick: no changes in 1000 years
Temperature under the mantle: 155 K
The characteristics of the mantle have a strong influence on the activity
of the body.
Gas (and dust) fluxes are severely quenched.
Under a 2 m thick porous dust layer, ~ 2 x 106 years could be needed to
devolatilize 1 m of an ice-rich layer..
In many cases, the mantle tends to grow, because the dust flux is very
reduced.
14. A yet unknown MBC in the outer Main Belt
Following Levison (2009), the violent dynamical evolution of the giant-
planet orbits required by the Nice model leads to the insertion of primitive
trans-Neptunian objects into the outer belt.
The captured bodies, composed of organic-rich materials, would have been
more susceptible to collisional evolution than typical main-belt asteroids.
These objects should be similar to the resonant Trojans and Hildas: D- or P-
type and probably organic-rich.
Input parameters P/ ?
a 4.0
e 0.3
Diameter (m) 1000
Dust/ice 1
Ice H2O, CO2, CO
Average density 434
(kg/m3)
15. A yet unknown MBC in the outer Main Belt
H2O flux
CO2 flux
CO flux
16. A yet unknown MBC in the outer Main Belt
Mantle forms
CO2 sublimation front
CO sublimation front
17. Conclusions
Small MBCs become quickly inactive due to rapid
degassing of upper layers. Exposed ice lasts very few time.
Ice buried under a thin porous mantle sublimates slowly,
while deep-buried ice can last for a very long time.
This is also an indication that the observed activity cannot be
sustained on "original" bodies, which soon after their
formation/injection into the Main Belt became inactive.
In the MB, an impact don’t need to necessarily expose ice to
activate a MBC: even a very small impact could activate a
MBC, bringing the heat closer to ice-rich layers
18. Conclusions
A number of bodies could exists with a faint gasesous activity
triggered by small impacts. These small impacts could have been
devolatilized the upper layers of MBCs.
A buried snow line must exist, defined by the depth at which
ice can survive for a very long time (T< 145 K). It depends on
heliocentric distance and the physical properties of the mantle.
What about the ice on 24 Themis?
24 Themis is big! A possible replenishment nechanism:
A thin porous insulating layer exists, shielding ice-rich layers
Micrometeoroids impacts erodes the surface, bringing Sun
heat closer to the surface and triggering a faint ice sublimation
No dust flux, gas recondenses on the surface and slowly
sublimates
Micrometeoroids impacts erodes the surface…