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.
Space weather and potential impact on earth’s climate dec 19 10 v2Poramate Minsiri
This document discusses space weather and its potential impacts on Earth's climate and seismic activity. It provides an overview of the solar system and its dynamics, as well as how our solar system interacts with the Milky Way galaxy and larger universe. Recent observations have found evidence that the outer boundaries of our solar system are being compressed as we pass through Galactic clouds, allowing more cosmic rays and energetic particles to enter the inner solar system. This could affect Earth's climate and increase seismic activity. The document also discusses changes observed on other planets in our solar system, such as the growth of dark spots on Pluto and changes in cloud cover on Mars.
Probing Extreme Physics With Compact ObjctsSérgio Sacani
This document discusses compact objects like white dwarfs, neutron stars, and black holes, which exist under extreme conditions of density, temperature, gravity, and magnetism. It summarizes key findings and areas of ongoing research regarding these objects. In particular, it highlights how studying the cooling of neutron stars can help constrain their interior physics, and how quantum electrodynamics effects in strong magnetic fields can be probed by observing the spectra and polarization of neutron star atmospheres.
The Solar System consists of the Sun and objects bound to it by gravity, including 8 planets. The 4 inner terrestrial planets - Mercury, Venus, Earth, and Mars - are primarily rocky. The 4 outer gas giants - Jupiter, Saturn, Uranus, and Neptune - are massive and gaseous. Between Mars and Jupiter is the asteroid belt. Comets originate from the Kuiper belt beyond Neptune and have highly elliptical orbits. Each planet has unique characteristics such as atmospheric composition, rotation period, and presence of moons and rings.
The document is a collection of images from NASA's Solar and Heliospheric Observatory (SOHO) spacecraft, along with brief captions describing each image. The images show various phenomena on the sun's surface and atmosphere such as solar prominences, the corona, coronal mass ejections, sunspots, and oscillations within the sun's interior. They demonstrate what the sun looks like in different wavelengths of light beyond the visible spectrum.
A super earth transiting a naked-eye starSérgio Sacani
This document summarizes the detection of transits of an exoplanet orbiting the star 55 Cnc, using photometry from the MOST space telescope. The transits match the period, phase, duration, and depth predicted for the innermost planet of 55 Cnc, designated 55 Cnc e. Analysis of the transit data indicates the planet has a mass of 8.57 Earth masses, a radius of 1.63 Earth radii, and a dense composition of rock and iron. This makes 55 Cnc e similar to other dense super-Earth exoplanets in short orbits, unlike lower-density super-Earths further from their stars. The brightness of 55 Cnc will enable further study of this transiting exoplanet system.
The nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
IB Astrophysics - cosmology - Flippingphysics by nothingnerdyNothingnerdy
The document summarizes key concepts in cosmology, including Olbers' paradox, the expanding universe, the Big Bang theory, and evidence like the cosmic microwave background radiation. It discusses how the universe originated approximately 13.7 billion years ago in a massive expansion from a single point. The universe is still expanding today, and its fate depends on whether it has a flat, closed, or open geometry based on its total mass density. While most mass is dark matter and dark energy, their exact nature remains unknown. International space projects seek to further understand these cosmological questions through observation and research.
1) The growth of the first stars was halted by ultraviolet radiation feedback from the stars themselves.
2) Radiation from the protostar evaporated the circumstellar accretion disk when the star's mass reached 43 times the mass of the Sun.
3) These massive primordial stars may help explain the lack of pair-instability supernovae signatures in ancient metal-poor stars.
Space weather and potential impact on earth’s climate dec 19 10 v2Poramate Minsiri
This document discusses space weather and its potential impacts on Earth's climate and seismic activity. It provides an overview of the solar system and its dynamics, as well as how our solar system interacts with the Milky Way galaxy and larger universe. Recent observations have found evidence that the outer boundaries of our solar system are being compressed as we pass through Galactic clouds, allowing more cosmic rays and energetic particles to enter the inner solar system. This could affect Earth's climate and increase seismic activity. The document also discusses changes observed on other planets in our solar system, such as the growth of dark spots on Pluto and changes in cloud cover on Mars.
Probing Extreme Physics With Compact ObjctsSérgio Sacani
This document discusses compact objects like white dwarfs, neutron stars, and black holes, which exist under extreme conditions of density, temperature, gravity, and magnetism. It summarizes key findings and areas of ongoing research regarding these objects. In particular, it highlights how studying the cooling of neutron stars can help constrain their interior physics, and how quantum electrodynamics effects in strong magnetic fields can be probed by observing the spectra and polarization of neutron star atmospheres.
The Solar System consists of the Sun and objects bound to it by gravity, including 8 planets. The 4 inner terrestrial planets - Mercury, Venus, Earth, and Mars - are primarily rocky. The 4 outer gas giants - Jupiter, Saturn, Uranus, and Neptune - are massive and gaseous. Between Mars and Jupiter is the asteroid belt. Comets originate from the Kuiper belt beyond Neptune and have highly elliptical orbits. Each planet has unique characteristics such as atmospheric composition, rotation period, and presence of moons and rings.
The document is a collection of images from NASA's Solar and Heliospheric Observatory (SOHO) spacecraft, along with brief captions describing each image. The images show various phenomena on the sun's surface and atmosphere such as solar prominences, the corona, coronal mass ejections, sunspots, and oscillations within the sun's interior. They demonstrate what the sun looks like in different wavelengths of light beyond the visible spectrum.
A super earth transiting a naked-eye starSérgio Sacani
This document summarizes the detection of transits of an exoplanet orbiting the star 55 Cnc, using photometry from the MOST space telescope. The transits match the period, phase, duration, and depth predicted for the innermost planet of 55 Cnc, designated 55 Cnc e. Analysis of the transit data indicates the planet has a mass of 8.57 Earth masses, a radius of 1.63 Earth radii, and a dense composition of rock and iron. This makes 55 Cnc e similar to other dense super-Earth exoplanets in short orbits, unlike lower-density super-Earths further from their stars. The brightness of 55 Cnc will enable further study of this transiting exoplanet system.
The nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
IB Astrophysics - cosmology - Flippingphysics by nothingnerdyNothingnerdy
The document summarizes key concepts in cosmology, including Olbers' paradox, the expanding universe, the Big Bang theory, and evidence like the cosmic microwave background radiation. It discusses how the universe originated approximately 13.7 billion years ago in a massive expansion from a single point. The universe is still expanding today, and its fate depends on whether it has a flat, closed, or open geometry based on its total mass density. While most mass is dark matter and dark energy, their exact nature remains unknown. International space projects seek to further understand these cosmological questions through observation and research.
1) The growth of the first stars was halted by ultraviolet radiation feedback from the stars themselves.
2) Radiation from the protostar evaporated the circumstellar accretion disk when the star's mass reached 43 times the mass of the Sun.
3) These massive primordial stars may help explain the lack of pair-instability supernovae signatures in ancient metal-poor stars.
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.
This chapter discusses small solar system bodies like dwarf planets, asteroids, meteoroids, comets, and Kuiper Belt objects. It describes their properties and classifications. Key points include that dwarf planets like Pluto and Eris have been discovered in the outer solar system, along with their moons. Asteroids exist in the main belt between Mars and Jupiter and some have orbits that cross Earth's. Comets contain ice and debris and have tails when close to the Sun. Impacts from these small bodies have caused mass extinctions on Earth in the past.
This document summarizes observations of the debris disk around the subgiant star κ CrB using Herschel and Keck. Herschel spatially resolved images of the debris disk, the first such images of a disk around a subgiant star. Keck radial velocity monitoring provided evidence for a second planetary companion around κ CrB. Keck adaptive optics imaging placed an upper limit on the mass of this companion. Modeling of the Herschel images showed the dust is broadly distributed but could not distinguish between a single wide belt or two narrow belts. The observations are consistent with dynamical depletion or collisional erosion clearing the inner regions of the disk.
The document discusses astrophysics concepts related to stars, including:
1. The main energy source of stars is hydrogen fusion, which occurs through either the proton-proton chain or CNO cycle depending on the star's core temperature.
2. A star's luminosity, temperature, radius, mass, chemical composition, and age can be used to characterize it. Its luminosity can be calculated using the Stefan-Boltzmann law.
3. A star's spectrum provides information about its surface temperature, chemical composition, and whether it is part of a binary 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.
Explanation for the Increase in the Expansion of the Universe through Gravita...IOSR Journals
This thesis explains the expansion rate of the universe and establishes the relationship between the expansion rate and the number of black holes in the universe andInspiralling binary neutron stars, white dwarfs and binary systems of black holes , black hole merges and supernovae, hyper novae and all other catastrophic explosions taking place in the universe and which in turn establishes the relation between the expansion rate of the universe and the age of the universe.
This paper considers the plausibility of time dilation effects shown in the film Interstellar. It calculates that for an hour to pass on a planet orbiting a 100 million solar mass black hole while 7 years pass on Earth, the planet would need to orbit at 2.95 astronomical units from the black hole. However, this distance is inside the minimum stable orbit, so the planet would not be able to maintain that orbit around a non-rotating black hole. A rotating black hole could allow for a stable orbit at that distance. The paper also finds that travel times depicted in the film between the planet and a safe orbit are implausibly short.
The document provides an overview of the formation and components of our solar system. It describes how the solar system formed from a large cloud of gas and dust called the solar nebula. It then discusses each planet individually, including their physical characteristics such as size, composition, and orbital properties. It also briefly touches on other objects in our solar system such as comets, asteroids, and dwarf planets like Pluto.
NEUTRON STARS - UNIQUE COMPACT OBJECTS OF THEIR OWNIJRST Journal
This paper outlines the study of neutron stars right from the early
theoretical predictions and observations by various astrophysicists which
gradually aroused huge interests among the scientific community, to the
latest developments in the scientific analysis of the behavior of the different
categories of compact objects. Although white dwarfs, neutron stars, brown
dwarfs, Black Holes etc.fall under the category of compact objects, each of
them is unique in its own way.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
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
There are several types of ultra-compact binary star systems that orbit each other with periods of less than an hour. These systems emit gravitational waves due to their strong gravitational fields changing over time. The Laser Interferometer Space Antenna (LISA) mission aims to detect these gravitational waves. While current ground-based detectors cannot detect the waves from ultra-compact binaries, LISA may be able to do so due to observing from space. The document provides data on four example binary systems and calculates their orbital decay rates and the strain of the gravitational waves emitted.
The ALMA observations of the Fomalhaut debris disk resolve the ring of parent bodies that produce the dust. The parent body ring has a sharp inner edge at 135 AU and outer edge at 151 AU, giving it a width of 16 AU. The ring has a vertical scale height corresponding to an opening angle of 1 degree. The observations are consistent with the ring being confined by shepherd planets. The dust in the ring has a total mass of 0.017 Earth masses, requiring the parent body population to be at least 1.7 Earth masses.
The document provides information about outer solar system objects including Trans-Neptunian objects, Centaurs, Kuiper Belt objects, asteroids, comets, and dwarf planets. It discusses their classification, composition, formation processes, and what they reveal about the early solar system. Images show various outer solar system bodies like Pluto, Eris, asteroids, and comets, helping to illustrate their characteristics and relative sizes.
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.
NEAR-IR SPECTRAL OBSERVATIONS OF THE DIDYMOS SYSTEM - DAILY EVOLUTION BEFORE ...Sérgio Sacani
1) Near-IR spectroscopic observations were taken of the Didymos system daily before and after the DART impact to study the evolution of the ejecta cloud.
2) The spectral features remained consistent with an S-type classification, confirming that Didymos and Dimorphos are composed of similar silicate material. This supports models of binary asteroid formation via rotational breakup.
3) In the first 38 hours after impact, the spectral slope decreased as coarser ejecta dominated but then increased again as the ejecta cloud dispersed, returning to the pre-impact slope within a week. No "fresh" non-weathered material was detected from Dimorphos' subsurface.
Pawan Kumar Relativistic jets in tidal disruption eventsBaurzhan Alzhanov
- Fast radio bursts (FRBs) are short, intense radio pulses that last about 1 millisecond. One FRB source produced multiple outbursts over several years.
- The leading model is that FRBs originate from young, highly magnetic neutron stars called magnetars. Charged particles are accelerated by magnetic reconnection, producing coherent curvature radiation observed as FRBs.
- FRBs provide insights into neutron star physics and energetic processes in magnetar magnetospheres. Predictions include observing FRB-like bursts at higher frequencies.
This document summarizes the results of a sub-mm survey of the Carina Nebula complex conducted with the LABOCA instrument on the APEX telescope. The survey mapped an area of 1.25° × 1.25° at 870 μm, revealing the morphology and distribution of cold dust clouds with masses down to a few solar masses. The total mass of clouds detected is estimated to be around 60,000 M☉. The cloud morphologies range from large clouds of several thousand solar masses to small diffuse clouds of only a few solar masses. The distribution of sub-mm emission generally agrees with Spitzer 8 μm maps, identifying clouds interacting with massive stars as well as infrared dark clouds. The survey provides crucial
The Expansion of the X-Ray Nebula Around η CarSérgio Sacani
1. The author analyzes over 20 years of Chandra X-ray images to measure for the first time the expansion of the X-ray nebula around η Carinae.
2. A combined Chandra image reveals a faint, nearly uniform elliptical shell surrounding the X-ray bright ring, with a similar orientation and shape as the Homunculus nebula but about 3 times larger.
3. The author measures proper motions of brighter regions associated with the X-ray emitting ring, such as the S-ridge and W-arc. Motions are consistent with optical studies of ejecta from the 1840s Great Eruption.
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.
This chapter discusses small solar system bodies like dwarf planets, asteroids, meteoroids, comets, and Kuiper Belt objects. It describes their properties and classifications. Key points include that dwarf planets like Pluto and Eris have been discovered in the outer solar system, along with their moons. Asteroids exist in the main belt between Mars and Jupiter and some have orbits that cross Earth's. Comets contain ice and debris and have tails when close to the Sun. Impacts from these small bodies have caused mass extinctions on Earth in the past.
This document summarizes observations of the debris disk around the subgiant star κ CrB using Herschel and Keck. Herschel spatially resolved images of the debris disk, the first such images of a disk around a subgiant star. Keck radial velocity monitoring provided evidence for a second planetary companion around κ CrB. Keck adaptive optics imaging placed an upper limit on the mass of this companion. Modeling of the Herschel images showed the dust is broadly distributed but could not distinguish between a single wide belt or two narrow belts. The observations are consistent with dynamical depletion or collisional erosion clearing the inner regions of the disk.
The document discusses astrophysics concepts related to stars, including:
1. The main energy source of stars is hydrogen fusion, which occurs through either the proton-proton chain or CNO cycle depending on the star's core temperature.
2. A star's luminosity, temperature, radius, mass, chemical composition, and age can be used to characterize it. Its luminosity can be calculated using the Stefan-Boltzmann law.
3. A star's spectrum provides information about its surface temperature, chemical composition, and whether it is part of a binary 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.
Explanation for the Increase in the Expansion of the Universe through Gravita...IOSR Journals
This thesis explains the expansion rate of the universe and establishes the relationship between the expansion rate and the number of black holes in the universe andInspiralling binary neutron stars, white dwarfs and binary systems of black holes , black hole merges and supernovae, hyper novae and all other catastrophic explosions taking place in the universe and which in turn establishes the relation between the expansion rate of the universe and the age of the universe.
This paper considers the plausibility of time dilation effects shown in the film Interstellar. It calculates that for an hour to pass on a planet orbiting a 100 million solar mass black hole while 7 years pass on Earth, the planet would need to orbit at 2.95 astronomical units from the black hole. However, this distance is inside the minimum stable orbit, so the planet would not be able to maintain that orbit around a non-rotating black hole. A rotating black hole could allow for a stable orbit at that distance. The paper also finds that travel times depicted in the film between the planet and a safe orbit are implausibly short.
The document provides an overview of the formation and components of our solar system. It describes how the solar system formed from a large cloud of gas and dust called the solar nebula. It then discusses each planet individually, including their physical characteristics such as size, composition, and orbital properties. It also briefly touches on other objects in our solar system such as comets, asteroids, and dwarf planets like Pluto.
NEUTRON STARS - UNIQUE COMPACT OBJECTS OF THEIR OWNIJRST Journal
This paper outlines the study of neutron stars right from the early
theoretical predictions and observations by various astrophysicists which
gradually aroused huge interests among the scientific community, to the
latest developments in the scientific analysis of the behavior of the different
categories of compact objects. Although white dwarfs, neutron stars, brown
dwarfs, Black Holes etc.fall under the category of compact objects, each of
them is unique in its own way.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
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
There are several types of ultra-compact binary star systems that orbit each other with periods of less than an hour. These systems emit gravitational waves due to their strong gravitational fields changing over time. The Laser Interferometer Space Antenna (LISA) mission aims to detect these gravitational waves. While current ground-based detectors cannot detect the waves from ultra-compact binaries, LISA may be able to do so due to observing from space. The document provides data on four example binary systems and calculates their orbital decay rates and the strain of the gravitational waves emitted.
The ALMA observations of the Fomalhaut debris disk resolve the ring of parent bodies that produce the dust. The parent body ring has a sharp inner edge at 135 AU and outer edge at 151 AU, giving it a width of 16 AU. The ring has a vertical scale height corresponding to an opening angle of 1 degree. The observations are consistent with the ring being confined by shepherd planets. The dust in the ring has a total mass of 0.017 Earth masses, requiring the parent body population to be at least 1.7 Earth masses.
The document provides information about outer solar system objects including Trans-Neptunian objects, Centaurs, Kuiper Belt objects, asteroids, comets, and dwarf planets. It discusses their classification, composition, formation processes, and what they reveal about the early solar system. Images show various outer solar system bodies like Pluto, Eris, asteroids, and comets, helping to illustrate their characteristics and relative sizes.
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.
NEAR-IR SPECTRAL OBSERVATIONS OF THE DIDYMOS SYSTEM - DAILY EVOLUTION BEFORE ...Sérgio Sacani
1) Near-IR spectroscopic observations were taken of the Didymos system daily before and after the DART impact to study the evolution of the ejecta cloud.
2) The spectral features remained consistent with an S-type classification, confirming that Didymos and Dimorphos are composed of similar silicate material. This supports models of binary asteroid formation via rotational breakup.
3) In the first 38 hours after impact, the spectral slope decreased as coarser ejecta dominated but then increased again as the ejecta cloud dispersed, returning to the pre-impact slope within a week. No "fresh" non-weathered material was detected from Dimorphos' subsurface.
Pawan Kumar Relativistic jets in tidal disruption eventsBaurzhan Alzhanov
- Fast radio bursts (FRBs) are short, intense radio pulses that last about 1 millisecond. One FRB source produced multiple outbursts over several years.
- The leading model is that FRBs originate from young, highly magnetic neutron stars called magnetars. Charged particles are accelerated by magnetic reconnection, producing coherent curvature radiation observed as FRBs.
- FRBs provide insights into neutron star physics and energetic processes in magnetar magnetospheres. Predictions include observing FRB-like bursts at higher frequencies.
This document summarizes the results of a sub-mm survey of the Carina Nebula complex conducted with the LABOCA instrument on the APEX telescope. The survey mapped an area of 1.25° × 1.25° at 870 μm, revealing the morphology and distribution of cold dust clouds with masses down to a few solar masses. The total mass of clouds detected is estimated to be around 60,000 M☉. The cloud morphologies range from large clouds of several thousand solar masses to small diffuse clouds of only a few solar masses. The distribution of sub-mm emission generally agrees with Spitzer 8 μm maps, identifying clouds interacting with massive stars as well as infrared dark clouds. The survey provides crucial
The Expansion of the X-Ray Nebula Around η CarSérgio Sacani
1. The author analyzes over 20 years of Chandra X-ray images to measure for the first time the expansion of the X-ray nebula around η Carinae.
2. A combined Chandra image reveals a faint, nearly uniform elliptical shell surrounding the X-ray bright ring, with a similar orientation and shape as the Homunculus nebula but about 3 times larger.
3. The author measures proper motions of brighter regions associated with the X-ray emitting ring, such as the S-ridge and W-arc. Motions are consistent with optical studies of ejecta from the 1840s Great Eruption.
1) The document provides a summary of a course on high-energy astrophysics that the author took. It discusses various topics covered in the course including accretion disks, pulsars, black holes, supernovae, and more.
2) The author argues that high-energy astrophysics is important for understanding the universe and requests that the provost offer a similar course at their university.
3) Key concepts in high-energy astrophysics discussed include accretion and its relation to luminosity, binary star systems, properties of neutron stars and black holes, and x-ray emissions from astrophysical phenomena like supernovae.
This document summarizes an X-ray study of the supernova remnant G352.7-0.1 using data from XMM-Newton and Chandra observations. Prior observations revealed G352.7-0.1 has a shell-like radio morphology but center-filled thermal X-ray morphology, classifying it as a mixed-morphology supernova remnant. The new observations confirm the X-ray emission comes from the interior and is dominated by ejecta. Spectra from XMM-Newton are fit by a single thermal component with enhanced silicon and sulfur. Some Chandra spectra require a second thermal component to fit, with solar abundances providing a better physical model. No evidence of overionization was found. A neutron
A radiation belt of energetic protonslocated between Saturn and its ringsSérgio Sacani
Most magnetized planetsare known to possess radiation belts, wherehigh-energy charged particles are trapped inlarge numbers. The possibility that a radiationbelt could exist also in the confined regionbetween Saturn and its main rings has beenproposed on the basis of remote sensing obser-vations and simulations. It was not until thefinal 5 months of the Cassini mission that in situmeasurements were obtained from this regionwith the Magnetosphere Imaging Instrument(MIMI). This paper provides an overview ofthese measurements andtheir interpretation.
Is there an_exoplanet_in_the_solar_systemSérgio Sacani
We investigate the prospects for the capture of the proposed Planet 9 from other
stars in the Sun’s birth cluster. Any capture scenario must satisfy three conditions:
the encounter must be more distant than ∼ 150 au to avoid perturbing the Kuiper
belt; the other star must have a wide-orbit planet (a & 100 au); the planet must be
captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit
Solar System bodies. Here we use N-body simulations to show that these criteria may
be simultaneously satisfied. In a few percent of slow close encounters in a cluster,
bodies are captured onto heliocentric, Planet 9-like orbits. During the ∼ 100 Myr
cluster phase, many stars are likely to host planets on highly-eccentric orbits with
apastron distances beyond 100 au if Neptune-sized planets are common and susceptible
to planet–planet scattering. While the existence of Planet 9 remains unproven, we
consider capture from one of the Sun’s young brethren a plausible route to explain such
an object’s orbit. Capture appears to predict a large population of Trans-Neptunian
Objects (TNOs) whose orbits are aligned with the captured planet, and we propose
that different formation mechanisms will be distinguishable based on their imprint on
the distribution of TNOs
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
This document discusses meteor showers, asteroids, and comets. It notes that meteor showers occur yearly as Earth passes through debris from comets. It describes gaps in the distribution of asteroids called Kirkwood gaps, which are caused by resonances with Jupiter. It discusses evidence that asteroid families originated from collisions of larger parent bodies. The document also summarizes spacecraft visits to asteroids and comets, the different tails of comets, and forces like radiation pressure that affect small particles in the Solar System.
This document discusses pulsars and provides information about them. It begins by listing the group members and topics to be discussed, including an introduction to pulsars, their properties, discovery, formation from neutron stars, examples of the Crab pulsar and binary pulsars, and their radiating mechanism. It then provides details on the properties of pulsars, their extremely high density, classification, and the discovery of the first pulsar PSR B1919+21. The document summarizes how pulsars are formed from the collapse and rotation of massive stars, and discusses the Crab pulsar and binary pulsars in more detail. It concludes by outlining some applications and milestones of pulsar research, including their use in gravitational wave
This document summarizes an observational study of 92 southern stars using near-infrared interferometry to search for hot exozodiacal dust. The study found an 11% detection rate of bright dust, with 9 confirmed and 3 tentative detections. The detection rate decreased for later spectral type stars and increased with stellar age. No correlation was found between the presence of cold dust and hot dust. Spectral analysis suggested the dust is extremely hot or emission is dominated by scattered light in most cases. The results provide insights into the prevalence and properties of dust near the habitable zones of other stars.
This document presents a multiwavelength analysis of the merging galaxy cluster MACS J0416.1-2403 using observations from Chandra, JVLA, GMRT, and Hubble Space Telescope. The cluster consists of two main subclusters, NE and SW, separated by about 250 kpc. Chandra observations reveal the NE subcluster has a compact core and X-ray cavity, but is not a cool core. A density discontinuity is detected about 450 kpc southwest of the SW subcluster, likely caused by an interaction with a less massive structure detected in lensing maps. For both subclusters, the dark matter and gas components are well-aligned, suggesting MACS J0416.1-2403
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
The document summarizes a study of an extreme molecular cloud in the Antennae galaxies that has properties consistent with forming a globular cluster. ALMA observations reveal a cloud with a radius of 24 pc and mass greater than 5 million solar masses. While capable of forming a globular cluster, a lack of associated thermal radio emission indicates star formation has not yet begun to alter the environment, suggesting the cloud is in an early stage of evolution. For the cloud to be confined as observed, an external pressure over 10,000 times greater than typical interstellar pressure is required, supporting the theory that high pressures are needed to form globular clusters in extreme environments like mergers.
Universe and the Solar System (Lesson 1).pptxJoenelRubino3
SHS Earth and Life Grade 11 Lesson 1. This lesson discusses the compos of the universe, the origin of the universe, different hypotheses of the origin of the universe
Photometry of Giant Propellers in Saturn's RingsJakaylaRobinson
1) The document discusses analyzing images of "giant propellers" in Saturn's rings taken by Cassini during its Ring Grazing Orbit and Grand Finale.
2) The authors use images of the propeller "Santos-Dumont" taken on the lit and unlit sides to investigate how the propeller's brightness relates to its optical depth, by comparing predicted and observed brightness values.
3) They find the brightness ratio between prediction and observation is consistent in translucent parts of the propeller and ring, but varies more in opaque parts, helping evaluate differences between empty and opaque regions.
This document introduces the VLT-FLAMES Tarantula Survey, which obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. The survey aims to detect massive binary systems through variations in radial velocities and to characterize the properties of O- and B-type stars, addressing questions about stellar and cluster evolution. Spectral classifications are provided for newly discovered emission-line stars, including a new Wolf-Rayet star. The survey data and reduction procedures are overviewed, and upcoming analyses of the massive star properties are announced.
The document summarizes the timeline of major discoveries in cosmology, including Einstein's theory of general relativity, Hubble's discovery of the expanding universe, and the discovery of the cosmic microwave background radiation by Penzias and Wilson which provided evidence for the Big Bang theory. It then discusses supernovae types and their use in determining the accelerating expansion of the universe, for which three scientists - Perlmutter, Riess, and Schmidt - were awarded the 2011 Nobel Prize in Physics for their findings which suggested the universe is dominated by dark energy.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
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Anel pluto
1. Small particles in Pluto’s environment:
effects of the solar radiation pressure
P. M. Pires dos Santos, S. M. Giuliatti Winter, R. Sfair, & D. C. Mour˜o
a
arXiv:1108.0712v1 [astro-ph.EP] 2 Aug 2011
August 4, 2011
Abstract
Impacts of micrometeoroids on the surfaces of Nix and Hydra can produced dust particles and form a
ring around Pluto. However, dissipative forces, such as the solar radiation pressure, can lead the particles
into collisions in a very short period of time. In this work we investigate the orbital evolution of escaping
ejecta under the effects of the radiation pressure force combined with the gravitational effects of Pluto,
Charon, Nix and Hydra. The mass production rate from the surfaces of Nix and Hydra was obtained
from analytical models. By comparing the lifetime of the survived particles, derived from our numerical
simulations, and the mass of a putative ring mainly formed by the particles released from the surfaces of
Nix and Hydra we could estimate the ring normal optical depth. The released particles, encompassing
the orbits of Nix and Hydra, temporarily form a 16000 km wide ring. Collisions with the massive bodies,
mainly due to the effects of the radiation pressure force, remove about 50% of the 1µm particles in 1 year.
A tenuous ring with a normal optical depth of 6 × 10−11 can be maintained by the dust particles released
from the surfaces of Nix and Hydra.
Keywords: Kuiper belt: general - Planets and satellites: individual: Pluto
1 Introduction
Since the discovery of Nix and Hydra by Weaver et al. (2006) much effort has been made in order to find new
satellites and a tenuous ring located in the Pluto system. As proposed by many authors this ring would be
essentially composed by material produced from collisions between Pluto’s satellites and small Kuiper Belt
debris (Thiessenhusen et al. 2002; Stern et al. 2006; Steffl & Stern 2007).
Thiessenhusen et al. (2002) have showed that a dust cloud, mainly formed by ejecta produced by impacts
of micrometeoroids on the surface of Charon, can exist around Pluto and Charon. In their model the orbits
of the ring particles were disturbed only by the gravitational effects of the two massive bodies. A dissipative
force, such as the solar radiation pressure, was not taken into account. This dust cloud would be very tenuous
with a maximum optical depth of 3 × 10−11 .
A discussion on the collisional velocities of impactors from the Kuiper belt on the surfaces of Pluto’s
satellites is presented in Stern et al. (2006). By making some assumptions, such as the ring is composed by
ice particles with a mean lifetime of 105 yr, they could estimate a characteristic optical depth of τ = 5 × 10−6
for a ring located between the orbits of Nix and Hydra.
The first observational constraint on a Pluto’s ring was presented by Steffl & Stern (2007). Based on
the data obtained by the Hubble Space Telescope they argued that the Pluto system has no ring with
τ > 1.3 × 10−5 . If Pluto has a ring system it is either comparable to the Jupiter’s rings or it is a narrow ring
confined in less than 1500 km in width. They also estimated a lifetime of 900 yr for such a ring system based
on its optical depth constraint.
Stern (2009) discussed the dynamical evolution of the escaping ejecta from the surfaces of Pluto, Charon,
Nix and Hydra, in an attempt to propose an alternative hypothesis on the similarity found in the colors and
albedos of Pluto’s satellites. He found that the ejecta from Nix and Hydra can reach one another and also
the surface of Charon. In this analysis Stern (2009) considered the dissipative effect caused by the drag from
Pluto’s escaping atmosphere. He proposed that the similarities can be explained by the exchanging of the
1
2. Parameters Pluto
a (AU)a 39.482
ea 0.249
i (deg)a 17.140
D (km)b [2294]
M (kg)b 1.3 × 1022
Table 1: Parameters of the orbit of Pluto related to the Sun. a Semi-major axis, eccentricity and inclination
of Pluto are derived from Murray & Dermott 1999. b Diameter and mass of Pluto are given by Tholen et
al. 2008. Square bracket indicates assumed quantity.
ejecta material. However Canup (2011) argued that, given their current masses, similar albedos would imply
in high densities values for Nix, Hydra and Charon.
The motion of a dust grain in orbit around a planet can also be affected by the solar radiation force.
The Poynting-Robertson drag (PR drag hereafter) and the radiation pressure (RP component hereafter) are
components of the solar radiation force. The PR drag is mainly responsible for the collapse of the particle’s
orbit leading to a collision with the planet. The main effect of the RP component is the oscillation of the
particle’s orbital eccentricity as a function of the planet orbital period. If this oscillation is large enough the
particle can collide with the central body or it can be ejected from the system in a short period of time. A
detailed study of this dissipative force is presented in Burns et al. (1979).
In section 2 we firstly analysed the C parameter which is the ratio between the solar radiation pressure
and the gravity of Pluto (Hamilton & Krivov, 1996). This parameter allow us to verify the importance of the
solar radiation pressure in Pluto’s environment. We also numerically simulated a sample of ejecta particles
from Nix and Hydra’s surfaces under the effects of solar radiation force and the gravity of the four massive
bodies. In our model Pluto is an eccentric orbit and its tilted rotational axis was included. In section 3 we
estimated the mass production rates of dust ejecta from the surfaces of Nix and Hydra through an analytical
model. The combined results, analytical and numerical, can help us to constraint a normal optical depth of
a putative ring system. Our conclusions are presented in the last section.
2 Solar radiation force acting on dust particles
In this section we analysed the fate of the ejecta produced from the surfaces of Nix and Hydra under the
gravitational effects of the massive bodies and the RP component.
2.1 The strength of the perturbing force
First of all we calculated the dimensionless parameter C given by (Hamilton & Krivov, 1996)
9 n Fs r2
C= Qpr (1)
8 ns GM cρs
The C parameter gives the relative strength between the solar radiation force and the planetary gravity,
where n is the particle’s mean motion about the planet and ns is the mean motion of the planet around the
Sun, r is the position vector of the particle and r=|r|, Fs is the solar radiation flux density at the heliocentric
distance of Pluto, Qpr is the radiation pressure efficiency factor, c is the speed of light, G is the gravitational
constant, M is the mass of Pluto, and ρ and s are the density and the radius of the grain, respectively.
The variation of C as a function of the plutonian radius can be seen in Fig. 1 for two particles of sizes 1
and 10µm in radius. The orbital elements and physical parameters of Pluto are listed in Table 1, where a
is the semi major axis in Astronomical Unit (AU), e is the eccentricity, i is the inclination in degrees, D is
the diameter in km and M is the mass in kg (Murray & Dermott 1999, Tholen et al. 2008). The grains are
adopted to be spherical with an uniform density equals to 1g cm−3 and Qpr was assumed to be 1 (Burns et
al. 1979).
2
3. 3
10
2
10
Parameter value
1
10
0
10
-1
10
-2
10
-3
10 1 510 100 1000
Distance (plutonian radii)
Figure 1: Parameter C as a function of the distance of Pluto for a spherical grain with 1 (· · · ) and 10µm
(—) in radius and density equals to 1g cm−3 . The gray area represents the radial distance between the orbits
of Nix and Hydra.
As expected the smaller particle is more sensitive to the effects of the solar radiation pressure than the
larger particle. The strength of C is ∼ 10 for a 1µm sized particle and ∼ 1 for a 10µm sized particle placed
between the orbits of Nix and Hydra, about 45-58 plutonian radii (the gray area shown in Fig. 1).
We compared the results presented in Fig. 1 with a previous analysis by Sfair & Giuliatti Winter (2009)
on the orbital evolution of small particles located at the µ and ν uranian rings. Their results showed that C
is ∼ 1 for a 1µm sized particle (see their Fig. 2), smaller than the value shown in our Fig. 1. Their numerical
simulations did confirm that the solar radiation pressure has an important effect on the orbital evolution of
dust particles located in the µ and ν rings. Although Pluto is far from Sun, its small size, relative to the giant
planets, becomes the solar radiation pressure an important force to be taken into account in the analysis of
the orbital evolution of dust particles in Pluto’s environment (Pires dos Santos et al. 2010).
2.2 Numerical simulations
The equation of motion of a dust particle with cross section A, in an inertial reference frame, under the effects
of the solar radiation force can be written as
Fs AQpr r
˙ ˆ v
˙
mv = 1− S− (2)
c c c
ˆ
where r is the particle’s radial velocity, S is a unit vector in the direction of the incident radiation, and v is
˙
the velocity vector of the particle relative to the Sun (Burns et al. 1979). This force (eqn. 2) is composed by
a velocity-independent component (RP component) and a velocity-dependent component (PR drag).
The PR drag has long period effects while the RP component provokes, in a very short period of time, a
variation in the eccentricities of the dust particles which can lead to a collision or escape from the system.
Only for completeness we numerically simulated the effects of the PR drag in a sample of particles, with
radius ranging from 1 to 10µm, initially in circular orbits around Pluto. By assuming a constant decay rate
the 1µm sized particles will collide with Pluto in 106 years. Considering circumplanetary and equatorial
particles, this value is comparable to the characteristic orbital decay time derived by the analytic expression
3
4. Parameters Charon Nix Hydra
a (km) 19570.3 (a0 ) 49240. 65210.
e 0.0035 0.0119 0.0078
i (◦ ) 96.168 96.190 96.362
diameter (km) 1212 88 72
mass (kg) 1.5 × 1021 5.8 × 1017 3.2 × 1017
Table 2: Orbital and physical parameters derived by Tholen et al. (2008). Epoch JD 2452600.5. The
parameters of the orbit of Charon are relative to Pluto, the parameters of the orbits of Nix and Hydra are
relative to the center of mass of the Pluto-Charon system. The masses of Nix and Hydra were obtained
assuming the density equals to 1.63 g cm−3 .
given in Burns et al. (1979). By the other hand the RP causes an increase in the eccentricities of these dust
particles in a short period of time, less than 10 years. Therefore we do not take into account the long period
effects of the PR drag in our numerical simulations.
Stern (2009) has proposed that the ejecta escaped from the surfaces of Nix and Hydra can be responsible
for covering these two satellites and also the surface of Charon. Dust particles can escape from a parent
body when the ejecta velocity is larger than the escape velocity (vesc ) of that body. The range of the
characteristic ejecta velocity, produced from impacts of Kuiper belt objects in the Pluto system, is 0.01-
0.2 km s−1 (Stern, 2009). From the parameters derived from Tholen et al. (2008), the escape velocities of Nix
and Hydra are 0.042 km s−1 and 0.034 km s−1 , respectively, smaller than the characteristic ejecta velocity.
Pluto and Charon’s escape velocities are larger than 0.2 km s−1 and they will retain the ejecta produced
from the impacts on their surfaces.
Our initial sample of dust particles was perpendicularly ejected from the surfaces of Nix and Hydra
with initial velocity vi = 1.0vesc , large enough to escape from the parent satellite. Ejected particles with
vi > 1.0vesc can escape from the system in a very short period of time. The escaping ejecta, pure ice grains
with radii of 1, 5 and 10µm and scattering properties of an ideal material, are under the combined effects of
the gravity field of the four massive bodies and the RP. The initial conditions of the four massive bodies are
listed in Tables 1 and 2.
We take into account the variation of the solar flux during the orbital period of Pluto due to its large
eccentricity (Table 1). The planetary shadow and the light reflected from the planet were neglected in
first approximation, both effects are weaker than those caused by the RP (Hamilton & Krivov, 1996). The
Yarkovsky effect was also neglected since this effect is irrelevant for particles in the micrometer-sized range.
Figure 2 presents the values of the semimajor axis versus eccentricity after 1, 10 and 100 years. After
1 year (Fig. 2a) the ejected particles are distributed in a region which encompasses the orbits of Nix and
Hydra, located at 2.5a0 and 3.3a0 , respectively, where a0 = 19570.3 km (Table 2). The lifetime of the ejecta
from Nix and Hydra is determined by collisions with Pluto and by ejections from the system. After 100 years
only 7% of the total amount of particles is still in orbit around Pluto.
The oblateness of the central body can decrease the variation of the eccentricity of the dust particles
caused by the RP component (Sfair & Giuliatti Winter, 2009). By adopting the value of Pluto gravity
coefficient, as proposed by Beauvalet et al. (2010) to be O(−4), we verified that this effect can be neglected
near the orbits of Nix and Hydra.
Our results did not corroborate the results presented in Stern (2009). In our numerical simulations about
45% of the total amount of the dust particles collide with Pluto and Charon. Only a small fraction, less than
1%, of the ejecta produced by the small satellites, Nix and Hydra, can reach each other.
In the next section we analysed the mass and the normal optical depth of a ring generated by impacts of
interplanetary dust particles (IDPs), assumed to be interplanetary micrometeoroids, on the surfaces of Nix
and Hydra. The comparison of the numerical results and the mass production rate will help us to place an
upper limit to the ring normal optical depth generated by this mechanism.
4
5. 0.8
Eccentricity
0.6
0.4
0.2
0
0 1 2 3 4 5
Barycentric semimajor axis (a0)
0.8
Eccentricity
0.6
0.4
0.2
0
0 1 2 3 4 5
Barycentric semimajor axis (a0)
0.8
Eccentricity
0.6
0.4
0.2
0
0 1 2 3 4 5
Barycentric semimajor axis (a0)
Figure 2: Diagram of the instantaneous barycentric semimajor axis as function of the eccentricity for a set of
micrometer-sized particles (1µm, 5µm and 10µm) ejected from the surfaces of Nix and Hydra. The satellites
are located at 2.5a0 (Nix) and 3.3a0 (Hydra). Top: timespan of 1 year, middle: 10 years, bottom: 100 years.
5
6. 3 Ejecta Particles
Firstly the mass production of the ejected dust particles will be calculated by analysing the mass flux of
impactors at Pluto’s region and the yield parameter.
3.1 Mass production rate
Interplanetary meteoroid bombardment on the surfaces of planetary satellites was suggested as a possible
mechanism to produce and maintain dust rings around planets in the Solar System (see, e.g., Kruger et
al. 2000, Krivov et al. 2003). This section follows the approach summarized in Sfair & Giuliatti Winter (2011).
Although the dust fluxes beyond 18AU from the Sun have not been experimentally confirmed, estimatives
have been used to characterize the dust fluxes at all the giant planets distances and at the perihelion of Pluto
∞
(Krivov et al. 2003, Porter et al. 2010). Thus, we assume that the mass flux of impactors (Fimp ) at Pluto is
similar to the mass flux at Neptune, i.e., 1.0 × 10−16 kg m−2 s−1 (Porter et al. 2010), which corresponds to
the IDP flux at 30AU, close to the perihelion distance of Pluto. The superscript ∞ indicates that this value
was measured far from the central body and has to be corrected due to the gravitational focusing. However,
our results show that the diference between the mass flux of impactors far and close to Pluto is of O(−3).
Therefore, we assumed the mass flux of impactors at Pluto region to be Fimp = 1.0 × 10−16 kg m−2 s−1 .
The value of the mass production rate (M + ) of each satellite depends on the ejecta yield (Y ) defined
as the ratio of the total ejected mass to the mass of the impactors. Koschny and Gr¨n (2001) presented a
u
definition for Y which depends on the fraction of ice-silicate in the target, and on the mass (mimp ) and the
velocity (vimp ) of the impactor. Assuming that Nix and Hydra have pure ice surfaces and mimp ∼ 10−8 kg,
which corresponds to a small object of about 100µm in radius, with vimp = 2.6 km s−1 , gives Y ∼ 100.
The mass production rate produced by a satellite can be given by (Krivov et al. 2003)
M + = Fimp Y S (3)
where S is the cross section area of the satellite. This gives values of M + equal to approximately 6 × 10−5
kg s−1 and 4 × 10−5 kg s−1 for Nix and Hydra, respectively.
For a steady ring its mass is directly proportional to the lifetime (T ) of its particles. The mass of
the ring can be roughly estimate from the values of the mass production rate and the lifetime of the ring
particles obtained from our numerical simulations. We assumed the mass production rate M + to be equal to
10−4 kg s−1 , which corresponds to the sum of the mass production rates of Nix and Hydra.
The mass of a ring at distance R from the planet and width dR can also be estimated from its normal
optical depth given a size distribution of the grains. We assume that the size distribution of the dust follows
a power law of the form dN = n(s)ds = Ks−q , where dN is the number of particles in the interval [s, s + ds],
q is a power-law index and K is a normalization constant. We assumed the same distribution of the Uranus
internal ring where q = 3.5 (Colwell & Esposito 1990). This type of distribution is the most common for
very small dust (Burns et al. 2001).
A ring located between the orbits of Nix and Hydra at R ∼ 57000 km and dR ∼16000 km, with a particle
size distribution of 1-10µm and an optical depth of τ = 5 × 10−6 (Stern et al. 2006) has a mass equals
to 108 kg. To accumulate this amount of mass, only generated by interplanetary meteoroid bombardments
on the surfaces of the satellites, it would be necessary that the lifetime of the particles were 4 × 104 years.
However, as has been shown the RP component has a significantly effect on the dust particles and drives the
ejecta material to collisions or to escape from the system in a timescale much shorter than 104 years.
A putative ring with the same characteristics as described before but with a normal optical depth of 10−8
has a mass Mr = 2.4 × 105 kg. It will take about 80 years to form such ring. To accumulate a mass of 105
kg, only supplied by collisions between Nix and Hydra and the IDPs, the Fimp should be a hundred times
larger, if we considered the same properties of the impactors and the targets.
Since the solar radiation pressure has a significantly effect on these dust ring particles, leading most of
them to collisions or ejections from the system in a timescale of about 1 year, we ruled out a normal optical
depth of order 10−6 as has been proposed by Stern et al. (2006).
A ring with a normal optical depth of 6 × 10−11 takes less than 1 year to accumulate a mass of 103 kg. In
this timescale about 98% of the ejecta from Nix and Hydra are still in the system assuring an equilibrium
between the production and the loss of the dust particles.
6
7. The adopted size distribution of the dust population (Burns et al. 2001) has a large quantity of very small
particles, an equivalence of 3000 particles of 1µm for each particle of 10µm in radius. Although about 80%
of the total amount of the 10µm sized particles survive for almost 10 years we assumed the lifetime of the
ring to be the lifetime of the set formed by particles of 1µm in radius.
4 Discussion
Even in a distant region, such as the Pluto’s environment, the effects of the solar radiation pressure have
to be considered in order to better estimate the orbital evolution of dust particles. This dissipative force
can be divided into two components: the PR drag and the RP component. Although the PR drag is
mainly responsible for the decreasing in the semimajor axis of the particle, it is a long period effect. The
RP component can dictate the lifetime of a dust particle (Sfair & Giuliatti Winter, 2009) by increasing its
eccentricity and leading this particle to close encounters with the massives bodies in a very short period of
time.
We numerically simulated a set of dust particles perpendicularly ejected from the surfaces of Nix and
Hydra. These particles are under the gravitational effects of Pluto, Charon, Nix and Hydra and the RP com-
ponent. Our simplified model assumed an isotropic flux of impactors on the surfaces of Nix and Hydra at
the perihelion distance of Pluto.
The released particles, encompassing the orbits of Nix and Hydra, temporarily form a 16000 km wide
ring. However, collisions with the massive bodies, mainly due to the effects of the RP component, remove
about 50% of the 1µm particles in 1 year.
The mass production rate from the surfaces of Nix and Hydra was obtained from analytical models. We
assumed the mass flux of impactors at Pluto’s region to be similar to the mass of flux at Neptune.
By comparing the lifetime of the survived particles, derived from our numerical simulations, and the mass
of a putative ring mainly formed by the particles released from the surfaces of Nix and Hydra we could
estimate the ring normal optical depth. As a result we find that a tenuous ring with a normal optical depth
of O(10−11 ) can be maintained by the escaping dust.
It is worth to point out that the interplanetary environment in the outer Solar System is not well known.
Many assumptions have to be made in order to estimate a normal optical depth of a putative ring encom-
passing the orbits of Nix and Hydra.
The New Horizons mission will offer the best opportunity to obtain in situ measurements of the dust
fluxes during all the way and beyond Pluto. It has a dust counter onboard which can detect particles with
masses larger than 10−12 g (Hor´nyi et al. 2008). The spacecraft data will help to validate the numerical and
a
theorical models.
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