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.
Andy Stine's Thesis--Neutron Star ModelsAndy Stine
This document is Andrew Stine's thesis on modeling the structure of neutron stars through equations of state. It begins with an overview of neutron star formation and composition, outlining the different layers from the atmosphere to the core. It then discusses the history and theory behind different equations of state used to model neutron star interiors. The document presents Stine's 1D model of neutron stars using two equations of state, and includes the Python code and results. The model matches previous predictions for the maximum mass of neutron stars using these equations of state.
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.
The article discusses two gaseous regions discovered that have a chemical composition close to that of the early universe before the first stars formed. This finding demonstrates that metals dispersed unevenly throughout the universe, with implications for when the first generation of stars could have formed. The early universe began with hydrogen, helium, and trace amounts of lithium produced by Big Bang nucleosynthesis. Later, the first stars enriched and ionized the universe with heavier elements, though it appears this process was nonuniform based on the discovery of pockets of nearly pristine gas.
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.
Jack Oughton - Quark Star Journal 01.pdfJack Oughton
A quark star is a hypothetical type of neutron star that may form if the intense gravitational pressure is enough to overcome nuclear forces, causing neutrons to break down into their constituent quarks. Quark stars are theorized to be even denser than neutron stars, with matter composed of "free quarks" or strange quark matter. They may form from certain massive neutron stars collapsing when beyond the Tolman-Oppenheimer-Volkoff limit. Quark stars could potentially be detected from being over-dense compared to neutron stars of the same mass, through energetic "quark nova" explosions, or by their relationship to mysterious magnetars and superluminous supernovae. However, direct evidence of strange quark matter has
Galaxies are organized into clusters and superclusters that are separated by immense voids, creating a vast foam-like structure known as the "cosmic web". The largest known structure is the Sloan Great Wall, which is nearly 1.5 billion light years in length. Dark matter seems to come in standard clumps of about 30 million solar masses and 300 parsecs across, with a temperature of about 10,000 K. The cosmological principle assumes the universe is uniform on large enough scales, both homogeneous meaning no preferred locations and isotropic meaning no preferred directions.
Neutrinos: The Chameleon in the Elementary Particle ZooAlan Poon
Neutrinos are extremely lightweight elementary particles that are produced by nuclear reactions in the Sun. The document discusses the challenges of detecting neutrinos due to their very small interaction cross-section. It summarizes the discoveries made by Ray Davis Jr. using a large tank of cleaning fluid to detect solar neutrinos, as well as the Sudbury Neutrino Observatory which was able to detect neutrinos via three different reactions and demonstrated that neutrinos oscillate between flavors as they travel, indicating neutrinos have mass. The document provides background on neutrino sources, detection challenges, and important experiments that advanced the understanding of neutrino properties.
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
Andy Stine's Thesis--Neutron Star ModelsAndy Stine
This document is Andrew Stine's thesis on modeling the structure of neutron stars through equations of state. It begins with an overview of neutron star formation and composition, outlining the different layers from the atmosphere to the core. It then discusses the history and theory behind different equations of state used to model neutron star interiors. The document presents Stine's 1D model of neutron stars using two equations of state, and includes the Python code and results. The model matches previous predictions for the maximum mass of neutron stars using these equations of state.
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.
The article discusses two gaseous regions discovered that have a chemical composition close to that of the early universe before the first stars formed. This finding demonstrates that metals dispersed unevenly throughout the universe, with implications for when the first generation of stars could have formed. The early universe began with hydrogen, helium, and trace amounts of lithium produced by Big Bang nucleosynthesis. Later, the first stars enriched and ionized the universe with heavier elements, though it appears this process was nonuniform based on the discovery of pockets of nearly pristine gas.
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.
Jack Oughton - Quark Star Journal 01.pdfJack Oughton
A quark star is a hypothetical type of neutron star that may form if the intense gravitational pressure is enough to overcome nuclear forces, causing neutrons to break down into their constituent quarks. Quark stars are theorized to be even denser than neutron stars, with matter composed of "free quarks" or strange quark matter. They may form from certain massive neutron stars collapsing when beyond the Tolman-Oppenheimer-Volkoff limit. Quark stars could potentially be detected from being over-dense compared to neutron stars of the same mass, through energetic "quark nova" explosions, or by their relationship to mysterious magnetars and superluminous supernovae. However, direct evidence of strange quark matter has
Galaxies are organized into clusters and superclusters that are separated by immense voids, creating a vast foam-like structure known as the "cosmic web". The largest known structure is the Sloan Great Wall, which is nearly 1.5 billion light years in length. Dark matter seems to come in standard clumps of about 30 million solar masses and 300 parsecs across, with a temperature of about 10,000 K. The cosmological principle assumes the universe is uniform on large enough scales, both homogeneous meaning no preferred locations and isotropic meaning no preferred directions.
Neutrinos: The Chameleon in the Elementary Particle ZooAlan Poon
Neutrinos are extremely lightweight elementary particles that are produced by nuclear reactions in the Sun. The document discusses the challenges of detecting neutrinos due to their very small interaction cross-section. It summarizes the discoveries made by Ray Davis Jr. using a large tank of cleaning fluid to detect solar neutrinos, as well as the Sudbury Neutrino Observatory which was able to detect neutrinos via three different reactions and demonstrated that neutrinos oscillate between flavors as they travel, indicating neutrinos have mass. The document provides background on neutrino sources, detection challenges, and important experiments that advanced the understanding of neutrino properties.
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
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.
1. Stellar evolution begins with the fragmentation of massive molecular clouds into smaller masses, each initiating their own star formation process.
2. As clouds collapse under gravity, the gravitational energy is transformed to radiation through molecular hydrogen and dust grains, causing an isothermal collapse. Further collapse becomes adiabatic as stars become opaque.
3. Stars sustain themselves through nuclear fusion, with more massive stars having shorter lifespans than less massive stars due to the greater energy requirements.
4. Stellar remnants include white dwarfs, neutron stars, pulsars, and black holes, depending on the star's original mass.
A presentation on the first cosmic explosions and how the Universe started to make heavy elements, by Monash University's Professor Alexander Heger from the Faculty of Science, School of Mathematical Science.
NASA's Juno spacecraft successfully entered Jupiter's orbit on July 4, 2016 after a 35-minute engine burn that decreased its velocity. This marks a major milestone for the mission, which aims to study Jupiter's composition, gravity field, magnetic field, and polar magnetosphere. Over the coming months, Juno will perform instrument checks and early science collection before its official science collection phase begins in October. The successful orbit insertion indicates the spacecraft is performing well and ready to investigate Jupiter and help scientists better understand the formation and evolution of giant planets.
Relativistic collapse and explosion of rotating supermassive stars with therm...Sérgio Sacani
1) The document describes general relativistic simulations of collapsing supermassive stars with and without rotation using a numerical code called Nada.
2) The simulations include effects of gas pressure, radiation, electron-positron pairs, and thermonuclear energy from hydrogen and helium burning.
3) Objects with a mass of around 5×105 solar masses explode if non-rotating with a metallicity over 0.007, while rotation lowers the threshold to 0.001. More massive objects have a higher critical metallicity for explosion.
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.
1) Neutron stars are the remnants of collapsed stars that have a mass greater than 1.4 solar masses. They form during type II supernovae following the collapse of massive red supergiant stars.
2) Pulsars are a type of neutron star that emit beams of electromagnetic radiation and appear to pulse due to their rotation. They were first discovered by Jocelyn Bell in 1967 through detecting their regular radio pulses.
3) Gravitational waves are ripples in spacetime caused by accelerating massive objects like neutron stars and black holes. Detecting gravitational waves from binary neutron star systems could provide insights into energetic cosmic events and test Einstein's theory of general relativity.
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.
The Orion Nebula is an emission nebula located in the constellation Orion where stars are actively forming. It is approximately 1,500 light years from Earth. The nebula contains the Trapezium cluster, which has four massive stars at its center that help illuminate the nebula. Scientists recently discovered a potential black hole at the center of the Trapezium cluster that is about 200 times the mass of our Sun and helps explain the motion and evolution of stars in the Orion Nebula.
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.
The document summarizes the period of the universe known as the Dark Age, which occurred between the emission of the cosmic microwave background radiation and the formation of the first stars. During this time, the universe was nearly homogeneous and dark as the first structures like galaxies and stars had yet to form. The Cold Dark Matter model and observations of the cosmic microwave background and distant galaxies provide evidence that the first stars likely formed around redshift 20, ending the Dark Age and beginning the process of reionization. The formation of these first stars required the presence of dark matter for structure to grow and cooling mechanisms like molecular hydrogen to allow gas to collapse into the progenitors of stars.
This document summarizes a detonating failed deflagration model of Type Ia supernovae. The model involves an off-center deflagration in a massive white dwarf that fails to unbind the star. Disturbances from the failed deflagration pollute the stellar surface and eventually evolve into isolated shock regions, serving as ignition points for detonations that result in supernova explosion. Preliminary results show ejecta composed of silicon and iron group elements, with an inner egg-shaped region surrounded by an incomplete burning shell. Explosion energies are around 1.3-1.5×1051 erg.
The document provides information about the Sun, including:
1) It is a huge gas ball at the center of the solar system that releases the energy equivalent of 100 billion atomic bombs per second through nuclear fusion reactions.
2) The two main fusion reactions are the proton-proton chain which converts hydrogen to helium, and the carbon-nitrogen-oxygen cycle.
3) Features of the Sun like sunspots and solar flares are caused by intense magnetic fields on its surface and atmosphere.
Lattice Energy LLC Changes in Solar Neutrino Fluxes Alter Nuclear Beta-decay ...Lewis Larsen
This document discusses a new theory of nucleosynthesis proposed by Lattice Energy LLC. The theory suggests that nucleosynthesis may occur in many locations beyond just stellar cores, fission reactors, and supernovae. It highlights evidence that nucleosynthesis could take place in places like the solar photosphere, corona, and flux tubes as well as in phenomena like lightning. The theory also suggests that solar neutrino fluxes may alter beta decay rates on Earth. If true, this new understanding of nucleosynthesis would significantly change current astrophysical paradigms.
The document provides information about Earth's moon, Luna. It discusses Luna's interior structure, including its crust, mantle, and core. It also describes Luna's surface features such as impact craters, maria (large dark plains), and regolith (loose rock and soil). Additionally, it discusses Luna's origin from a giant impact event about 4.5 billion years ago and its surface ages, with the highlands being the oldest at 4.4 billion years. The document also summarizes the Earth-Moon system, particularly how the Moon causes Earth's tides and is tide-locked in its orbit.
The document traces the history of atomic theory from ancient Greece to modern times. It discusses the ideas of early philosophers like Democritus who hypothesized atoms as indivisible particles. Experimental discoveries throughout the 18th-19th centuries led to identifying elements through spectroscopy and discovering over 55 elements near volcanoes. Niels Bohr incorporated these findings into his 1913 model of the atom with electrons orbiting in discrete shells. John Dalton further refined atomic theory in 1808 by postulating that atoms are uniform, distinct, and combine to form compounds. Later, J.J. Thomson discovered the electron and Ernest Rutherford deduced the nuclear structure of atoms through deflection experiments.
Astronomy - Stat eof the Art - CosmologyChris Impey
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the properties of the whole universe are covered, including Hubble expansion, the age and size, the big bang, and dark energy.
The document analyzes morphological and compositional data of the central peak of Tycho crater on the Moon. Analysis of high-resolution Chandrayaan-1 and LRO data reveals evidence of volcanic features on the central peak, including volcanic vents, lava ponds showing cooling cracks, lava flows, and domes. Compositionally, M3 data show the central peak is heterogeneous and dominated by high-Ca pyroxene-rich rocks, with an anorthositic base. These morphological and mineralogical features suggest the central peak underwent multiple modifications after impact, exposing deep lunar crustal materials through volcanism triggered by the impact event.
The structure of_irregular_galaxy_ngc3239Sérgio Sacani
This document appears to be a citation to a 1990 publication in the Publications of the Astronomical Society of the Pacific journal. However, without accessing the full text it is difficult to determine the key topics or essential information contained in the referenced publication based on the citation alone.
The two largest impact basins recently discovered at Vesta's south pole are Rheasilvia and Veneneia. Rheasilvia is ~500 km wide and 19 km deep, making it one of the largest impact features on Vesta. It has a central massif and spiral ridge patterns on its floor. Veneneia is an older, partially buried ~400 km basin located beneath Rheasilvia. Crater counts date both basins to 1-2 billion years old, indicating major geological resetting of Vesta occurred relatively recently.
Mars methane detection_and_variability_at_gale_craterSérgio Sacani
The document appears to be from the journal Science and contains data from the Curiosity rover measuring methane levels on Mars over multiple dates ("sols") since its landing in 2012. Tables show measurements of methane taken at night and day with information on atmospheric conditions. Average methane levels were calculated for groupings of sols labeled "low methane" and "high methane", with the high methane group showing levels over 7 parts per billion by volume.
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.
1. Stellar evolution begins with the fragmentation of massive molecular clouds into smaller masses, each initiating their own star formation process.
2. As clouds collapse under gravity, the gravitational energy is transformed to radiation through molecular hydrogen and dust grains, causing an isothermal collapse. Further collapse becomes adiabatic as stars become opaque.
3. Stars sustain themselves through nuclear fusion, with more massive stars having shorter lifespans than less massive stars due to the greater energy requirements.
4. Stellar remnants include white dwarfs, neutron stars, pulsars, and black holes, depending on the star's original mass.
A presentation on the first cosmic explosions and how the Universe started to make heavy elements, by Monash University's Professor Alexander Heger from the Faculty of Science, School of Mathematical Science.
NASA's Juno spacecraft successfully entered Jupiter's orbit on July 4, 2016 after a 35-minute engine burn that decreased its velocity. This marks a major milestone for the mission, which aims to study Jupiter's composition, gravity field, magnetic field, and polar magnetosphere. Over the coming months, Juno will perform instrument checks and early science collection before its official science collection phase begins in October. The successful orbit insertion indicates the spacecraft is performing well and ready to investigate Jupiter and help scientists better understand the formation and evolution of giant planets.
Relativistic collapse and explosion of rotating supermassive stars with therm...Sérgio Sacani
1) The document describes general relativistic simulations of collapsing supermassive stars with and without rotation using a numerical code called Nada.
2) The simulations include effects of gas pressure, radiation, electron-positron pairs, and thermonuclear energy from hydrogen and helium burning.
3) Objects with a mass of around 5×105 solar masses explode if non-rotating with a metallicity over 0.007, while rotation lowers the threshold to 0.001. More massive objects have a higher critical metallicity for explosion.
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.
1) Neutron stars are the remnants of collapsed stars that have a mass greater than 1.4 solar masses. They form during type II supernovae following the collapse of massive red supergiant stars.
2) Pulsars are a type of neutron star that emit beams of electromagnetic radiation and appear to pulse due to their rotation. They were first discovered by Jocelyn Bell in 1967 through detecting their regular radio pulses.
3) Gravitational waves are ripples in spacetime caused by accelerating massive objects like neutron stars and black holes. Detecting gravitational waves from binary neutron star systems could provide insights into energetic cosmic events and test Einstein's theory of general relativity.
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.
The Orion Nebula is an emission nebula located in the constellation Orion where stars are actively forming. It is approximately 1,500 light years from Earth. The nebula contains the Trapezium cluster, which has four massive stars at its center that help illuminate the nebula. Scientists recently discovered a potential black hole at the center of the Trapezium cluster that is about 200 times the mass of our Sun and helps explain the motion and evolution of stars in the Orion Nebula.
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.
The document summarizes the period of the universe known as the Dark Age, which occurred between the emission of the cosmic microwave background radiation and the formation of the first stars. During this time, the universe was nearly homogeneous and dark as the first structures like galaxies and stars had yet to form. The Cold Dark Matter model and observations of the cosmic microwave background and distant galaxies provide evidence that the first stars likely formed around redshift 20, ending the Dark Age and beginning the process of reionization. The formation of these first stars required the presence of dark matter for structure to grow and cooling mechanisms like molecular hydrogen to allow gas to collapse into the progenitors of stars.
This document summarizes a detonating failed deflagration model of Type Ia supernovae. The model involves an off-center deflagration in a massive white dwarf that fails to unbind the star. Disturbances from the failed deflagration pollute the stellar surface and eventually evolve into isolated shock regions, serving as ignition points for detonations that result in supernova explosion. Preliminary results show ejecta composed of silicon and iron group elements, with an inner egg-shaped region surrounded by an incomplete burning shell. Explosion energies are around 1.3-1.5×1051 erg.
The document provides information about the Sun, including:
1) It is a huge gas ball at the center of the solar system that releases the energy equivalent of 100 billion atomic bombs per second through nuclear fusion reactions.
2) The two main fusion reactions are the proton-proton chain which converts hydrogen to helium, and the carbon-nitrogen-oxygen cycle.
3) Features of the Sun like sunspots and solar flares are caused by intense magnetic fields on its surface and atmosphere.
Lattice Energy LLC Changes in Solar Neutrino Fluxes Alter Nuclear Beta-decay ...Lewis Larsen
This document discusses a new theory of nucleosynthesis proposed by Lattice Energy LLC. The theory suggests that nucleosynthesis may occur in many locations beyond just stellar cores, fission reactors, and supernovae. It highlights evidence that nucleosynthesis could take place in places like the solar photosphere, corona, and flux tubes as well as in phenomena like lightning. The theory also suggests that solar neutrino fluxes may alter beta decay rates on Earth. If true, this new understanding of nucleosynthesis would significantly change current astrophysical paradigms.
The document provides information about Earth's moon, Luna. It discusses Luna's interior structure, including its crust, mantle, and core. It also describes Luna's surface features such as impact craters, maria (large dark plains), and regolith (loose rock and soil). Additionally, it discusses Luna's origin from a giant impact event about 4.5 billion years ago and its surface ages, with the highlands being the oldest at 4.4 billion years. The document also summarizes the Earth-Moon system, particularly how the Moon causes Earth's tides and is tide-locked in its orbit.
The document traces the history of atomic theory from ancient Greece to modern times. It discusses the ideas of early philosophers like Democritus who hypothesized atoms as indivisible particles. Experimental discoveries throughout the 18th-19th centuries led to identifying elements through spectroscopy and discovering over 55 elements near volcanoes. Niels Bohr incorporated these findings into his 1913 model of the atom with electrons orbiting in discrete shells. John Dalton further refined atomic theory in 1808 by postulating that atoms are uniform, distinct, and combine to form compounds. Later, J.J. Thomson discovered the electron and Ernest Rutherford deduced the nuclear structure of atoms through deflection experiments.
Astronomy - Stat eof the Art - CosmologyChris Impey
Astronomy - State of the Art is a course covering the hottest topics in astronomy. In this section, the properties of the whole universe are covered, including Hubble expansion, the age and size, the big bang, and dark energy.
The document analyzes morphological and compositional data of the central peak of Tycho crater on the Moon. Analysis of high-resolution Chandrayaan-1 and LRO data reveals evidence of volcanic features on the central peak, including volcanic vents, lava ponds showing cooling cracks, lava flows, and domes. Compositionally, M3 data show the central peak is heterogeneous and dominated by high-Ca pyroxene-rich rocks, with an anorthositic base. These morphological and mineralogical features suggest the central peak underwent multiple modifications after impact, exposing deep lunar crustal materials through volcanism triggered by the impact event.
The structure of_irregular_galaxy_ngc3239Sérgio Sacani
This document appears to be a citation to a 1990 publication in the Publications of the Astronomical Society of the Pacific journal. However, without accessing the full text it is difficult to determine the key topics or essential information contained in the referenced publication based on the citation alone.
The two largest impact basins recently discovered at Vesta's south pole are Rheasilvia and Veneneia. Rheasilvia is ~500 km wide and 19 km deep, making it one of the largest impact features on Vesta. It has a central massif and spiral ridge patterns on its floor. Veneneia is an older, partially buried ~400 km basin located beneath Rheasilvia. Crater counts date both basins to 1-2 billion years old, indicating major geological resetting of Vesta occurred relatively recently.
Mars methane detection_and_variability_at_gale_craterSérgio Sacani
The document appears to be from the journal Science and contains data from the Curiosity rover measuring methane levels on Mars over multiple dates ("sols") since its landing in 2012. Tables show measurements of methane taken at night and day with information on atmospheric conditions. Average methane levels were calculated for groupings of sols labeled "low methane" and "high methane", with the high methane group showing levels over 7 parts per billion by volume.
This document presents an analysis of metallicity gradients in the Milky Way disk as observed by the SEGUE survey. The key findings are:
1) The radial metallicity gradient (change in [Fe/H] with Galactic radius R) becomes flatter at heights above the plane (|Z|) greater than 1 kpc.
2) The median metallicity at large |Z| is consistent with outer disk open clusters, which also exhibit a flat radial gradient of [Fe/H] ∼ -0.5.
3) A flat metallicity gradient at high |Z| has implications for models of thick disk formation, as different formation scenarios predict different metallicity patterns in the thick disk.
The document summarizes observations of volcanic features associated with the lunar craters Tycho and Aristarchus. It finds that Tycho contains more viscous lava flows with higher albedos, indicating compositional differences from Aristarchus. "Lakes" on the crater rims are thought to consist of lava from vents. The crater floors likely contain lava that drained into subsurface chambers. Late eruptions at Aristarchus obscured floor details. Widespread deposits around the craters resulted from base surges, indicating large explosions formed the craters. Counts of impact craters on volcanic features date them at different times, with Aristarchus about 1.6 times older than Tycho, though the floors are roughly the same age.
This very deep Chandra observation of the galaxy cluster Abell 2052 reveals detailed structure in the inner region, including bubbles evacuated by the radio lobes, compressed bubble rims, filaments, and loops. Two concentric shocks are seen, with a temperature rise measured for the inner shock. On larger scales, a spiral feature is detected, likely resulting from sloshing gas initiated by a previous merger. Initial evidence is also presented for previously unseen outer bubbles related to earlier black hole outbursts.
This document reports on observations of comet 103P/Hartley 2 made by the WISE space telescope in May 2010 and additional ground-based telescopes. The WISE observations detected the comet's coma, nucleus, and dust trail. Analysis of the coma suggests dust particles larger than those observed for comet 81P/Wild 2. The extracted nucleus is estimated to be 0.6 km in radius. Emission detected at 4.6 microns may be from carbon monoxide or carbon dioxide gas. Carbon dioxide production rates are estimated to be 3.5×1024 molecules per second. The dust trail was detected with an optical depth of 9×10-10 and minimum mass of 4×1010 kg. These observations provide
The document summarizes the analysis of layered deposits inside the 174 km diameter Terby impact crater located on Mars. Stratigraphic and mineralogical analysis using multiple datasets suggests the deposits were formed subaqueously during the Noachian period. The thickest sequences display fan delta morphologies indicative of prograding/onlapping sedimentation over time. Phyllosilicates detected within layers support a sedimentary environment with sustained liquid water. Erosion during the Hesperian sculpted the current landforms, with later fluvial and then aeolian activity. Terby crater thus preserves a geologic record spanning multiple periods of Mars' history.
1) Researchers have developed a new technique called mechanophotopatterning (MPP) that uses light irradiation and mechanical deformation to precisely control the topology of light-responsive elastomers, establishing a new patterning method.
2) Using MPP, a variety of surface topologies can be produced, making it potentially useful for applications. When optically thick samples are irradiated, they bow into 3D shapes with promising applications in advanced optics.
3) The intrinsic material properties of the polymers remain unchanged after deformation, allowing for diverse applications at the interface of cell biology and tissue engineering through dynamic control of mechanical feedback to cells.
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.
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
Catch me if_you_can_is_there_a_runaway_mass_black_hole_in_the_orion_nebula_cl...Sérgio Sacani
This document describes a study investigating the dynamical evolution of the Orion Nebula Cluster through N-body simulations. The simulations assume the cluster was initially much more compact than currently observed, based on evidence that a large fraction of gas was expelled during formation. This likely led to strong few-body relaxation effects early in the cluster's evolution. The simulations find that three-body interactions among massive stars could have ejected them from the cluster while also forming a very massive object through runaway stellar mergers. This object may have collapsed directly into a massive (~100 solar mass) black hole, which could explain the velocity dispersion of stars in the Trapezium system at the cluster core. The simulations further suggest this putative black hole has a ~70
How much of the human body is made up of stardust,Does atoms age and what is ...Healthcare consultant
How much of the human body is made up of stardust,Does atoms age and what is the age of atoms. If an atom or molecule becomes electrically charged by gaining or losing one or more electrons, it becomes an ion. If the atom gains electrons, it has a negative charge. If it loses electrons, it has a positive charge.
Too much pasta_for_pulsars_to_spin_downSérgio Sacani
This document summarizes a study investigating why no isolated X-ray pulsars have been observed with spin periods longer than 12 seconds. The researchers suggest this is due to a highly resistive layer in the inner crust of neutron stars, which is expected to be in a state called "nuclear pasta". Nuclear pasta has an irregular structure that increases electrical resistivity, limiting the spin-down of pulsars. Modeling the long-term magnetic field evolution incorporating a resistive nuclear pasta layer successfully reproduced the observed 12 second period limit. The results provide the first potential observational evidence for the existence of nuclear pasta in neutron star crusts.
The document discusses nucleosynthesis in the early universe and provides evidence for the Big Bang theory. It explains that during the first three minutes after the Big Bang, most deuterium combined to form helium and trace amounts of lithium. The predicted abundances of these light elements depend on the density of ordinary matter and agree well with observations, providing strong evidence for the Big Bang.
The article discusses observations from multiple space-based observatories that tracked a sun-diving comet, C/2011 N3 (SOHO), as it passed through the Sun's corona and disintegrated. The observatories captured details of the comet's flight path, emissions, and disintegration over time. Studying how comets interact with and break apart in the corona can provide insights into comet composition and the early solar system.
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.
This document summarizes an analysis of high resolution infrared spectra from the Cassiopeia A supernova remnant taken by the Spitzer Space Telescope. The analysis finds:
1) The reverse shock of the remnant is spherical to within 7%, though offset from the geometric center by 810 km/s.
2) Nucleosynthetic layers of Si and O show velocities differing by up to 500 km/s in some directions, indicating separation during the supernova.
3) Small-scale corrugated velocity structures seen in the ejecta likely formed during the supernova rather than by later instabilities at the remnant's reverse shock.
This document summarizes a study that uses cosmological simulations to model the formation of stellar halos around galaxies via the tidal disruption of accreted dwarf galaxies. The simulations follow the dynamical evolution and disruption of satellites from high redshift in a fully cosmological setting. The simulations produce stellar halos with masses and density profiles consistent with observations of the Milky Way and M31. The stellar halos show complex structures composed of well-mixed components, tidal streams, shells, and other substructures rather than smooth distributions.
Synestia Model explains the origin of the earth and moon as well as planets and other objects
Ribbon in Space around our Solar Syxstem discovered by IBEX – NASA
Will it have an impact on the current solar system and planet formation theory ?
IBEX Ribbon in space is the first indication of boundary layers in space. Boundary layers in space very likely played a major role in planet formations.
Further:
Researchers from the University of Michigan announced today the discovery of tiny amounts of water in the moon rocks brought back to Earth by the Apollo missions were native water, and not water brought by meteors or other objects from space crashing into it. This discovery could in turn invalidate the current theory of how our Moon was formed
Youxue Zhang -
Detection of anisotropic satellite quenching in galaxy clusters up to z ∼ 1Sérgio Sacani
Satellite galaxies in the cluster environment are more likely to be quenched than galaxies in the general field. Recently, it has
been reported that satellite galaxy quenching depends on the orientation relative to their central galaxies: satellites along the
major axis of centrals are more likely to be quenched than those along the minor axis. In this paper, we report a detection
of such anisotropic quenching up to z ∼ 1 based on a large optically selected cluster catalogue constructed from the Hyper
Suprime-Cam Subaru Strategic Program. We calculate the quiescent satellite galaxy fraction as a function of orientation angle
measured from the major axis of central galaxies and find that the quiescent fractions at 0.25 < z < 1 are reasonably fitted
by sinusoidal functions with amplitudes of a few per cent. Anisotropy is clearer in inner regions (<r200m) of clusters and not
significant in cluster outskirts (>r200m). We also confirm that the observed anisotropy cannot be explained by differences in
local galaxy density or stellar mass distribution along the two axes. Quiescent fraction excesses between the two axes suggest
that the quenching efficiency contributing to the anisotropy is almost independent of stellar mass, at least down to our stellar
mass limit of M∗ = 1 × 1010 M. Finally, we argue that the physical origins of the observed anisotropy should have shorter
quenching time-scales than ∼ 1 Gyr, like ram-pressure stripping, because, for anisotropic quenching to be observed, satellites
must be quenched before their initial orientation angles are significantly changed.
1. Chandra observations of the galaxy NGC 3351 revealed X-ray emission from its circumnuclear star-forming ring that is composed of numerous point-like sources embedded in diffuse hot gas.
2. The morphology of the X-ray emission is similar to but not identical with UV and H-alpha hot spots in the ring, which can be understood if star formation occurs through intermittent starbursts around the ring with different emissions tracing later evolutionary stages.
3. X-ray emission also extends beyond the ring, which is interpreted as outflowing gas from the ring into the disk and halo of NGC 3351, providing evidence for confined outflow near the plane but less restricted outflow perpendicular to
This document summarizes the life cycle of stars from birth to death. It discusses how stars like our Sun generate energy through nuclear fusion in their cores and describes the main sequence where most stars lie on the Hertzsprung-Russell diagram. As stars age and exhaust their fuel, they evolve into red giants or white dwarfs and some explode as supernovae at the ends of their lives. Understanding stellar evolution provides insights into the nature and fate of our Sun as well as the potential for life elsewhere.
A leaf falls from a tree, dancing in a breeze as it floats to the ground. In the playground across the street, laughing children tighten their grips to hold themselves on the merry-go-round. Back in the kitchen, a metal lid rattles under the pressure of steam escaping from the tea kettle below. Our daily experiences reveal much about how our world works. Thinking about everyday examples from the world around us helps form our basic understanding of physics.
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
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
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simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
TrustArc Webinar - 2024 Global Privacy SurveyTrustArc
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Science 2011-hosokawa-1250-3
1. Protostellar Feedback Halts the Growth of the First Stars in the
Universe
Takashi Hosokawa, et al.
Science 334, 1250 (2011);
DOI: 10.1126/science.1207433
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2. REPORTS
tostar was calculated directly from the mass in-
flux through the sink-cell boundary, whereas the
Protostellar Feedback Halts the Growth luminosity from the protostar, which controls
the radiative feedback, was calculated consistent-
ly from the protostellar model by using the de-
of the First Stars in the Universe rived accretion rate.
At its birth, a very small protostar of ∼0.01
Takashi Hosokawa,1,2* Kazuyuki Omukai,2 Naoki Yoshida,3 Harold W. Yorke1 M⊙ was surrounded by a molecular gas envelope
of ∼1 M⊙, which was quickly accreted onto the
The first stars fundamentally transformed the early universe by emitting the first light and by protostar. Atomic gas further out initially had
producing the first heavy elements. These effects were predetermined by the mass distribution of too much angular momentum to be accreted di-
the first stars, which is thought to have been fixed by a complex interplay of gas accretion and rectly, and a circumstellar disk formed. The in-
protostellar radiation. We performed radiation-hydrodynamics simulations that followed the growth falling atomic gas first hit the disk plane roughly
of a primordial protostar through to the early stages as a star with thermonuclear burning. The vertically at supersonic velocities. A shock front
circumstellar accretion disk was evaporated by ultraviolet radiation from the star when its mass was formed; behind the shock, the gas cooled and
43 times that of the Sun. Such massive primordial stars, in contrast to the often-postulated settled onto the disk, and its hydrogen was con-
extremely massive stars, may help explain the fact that there are no signatures of the pair-instability verted to the molecular form via rapid gas-phase
Downloaded from www.sciencemag.org on December 1, 2011
supernovae in abundance patterns of metal-poor stars in our galaxy.
heoretical studies and detailed computer the ionized region in its vicinity grows, and even-
T simulations show that the cradles of the
first stars were dense concentrations of
primordial gas, with masses of ~1000 that of the
tually the circumstellar disk is directly exposed
to the stellar ionizing radiation. The gas on the
disk surface is photoionized and heated and evap-
Sun. Such gas clouds formed through radiative orates away from the star-disk system. A semi-
cooling, with hydrogen molecules at the center analytical model of this process predicts that this
of a dark matter halo of 106 solar mass (M⊙), photoevaporation quenches the accretion flow
when the age of the universe was a few hundred of the disk material and puts an end to the stellar
million years (1). growth (8). However, the interplay between the
According to our current understanding of accretion flow and the stellar radiation is high-
star formation, a gas cloud’s dense core grav- ly dynamical and complex.
itationally contracts in a nonhomologous run- To identify the exact mechanism that halts
away fashion, in which the densest parts become the growth of a first star and to determine its final
denser faster than does the rest of the cloud (2–5). mass, we applied a method used for studying
In a primordial gas cloud, one or a few embryo the present-day massive star formation (9, 10)
protostars are formed near the center (2, 6). The to the case of the formation of the first stars in a
initial mass of these embryo protostars is only proper cosmological context. We followed the
≅0.01 M⊙; the bulk of the dense core material radiation hydrodynamic evolution in the vicin-
remains in the surrounding envelope and is sub- ity of an accreting protostar, incorporating ther-
sequently drawn toward the protostar (or proto- mal and chemical processes in the primordial gas
stars) through gravity. With the typical angular in a direct manner. We also followed the evolu-
momentum of dense cores, the centrifugal barrier tion of the central protostar self-consistently by
allows only a small amount of infalling gas to solving the detailed structure of the stellar inte-
accrete directly onto the star. Instead, a circum- rior with zero metallicity as well as the accretion
stellar disk is formed, and the gas is accreted flow near the stellar surface [supporting online
onto the central star through the disk (7). The material (SOM) text] (11, 12). We configured the
final mass of these first stars is fixed when the initial conditions by using the results of a three-
mass accretion terminates. However, when and dimensional (3D) cosmological simulation, which
how this termination occurs are largely unknown. followed the entire history from primeval density
Because the luminosity increases rapidly with fluctuations to the birth of a small seed protostar
protostellar mass, radiative feedback is expected at the cosmological redshift 14 (6). Specifical-
to regulate the mass accretion and ultimately shut ly, when the maximum particle number density
off the accretion flow, setting the final mass of reached 106 cm−3 in the cosmological simulation,
the first stars. A primordial star more massive than we considered a gravitationally bound sphere of
Fig. 1. (A to D) Evolution of the stellar radius,
a few tens times the mass of the Sun radiates a radius 0.3 pc around the density peak, which en- bolometric luminosity, evolutionary time scales, and
copious amount of hydrogen-ionizing photons closed a total gas mass of ≅300 M⊙. We reduced ionizing (hν ≥ 13.6 eV) and dissociating (11 eV ≤
(>13.6 eV). As an accreting star grows in mass, the 3D data to an axisymmetric structure by av- hν ≤ 13.6 eV) photon number luminosity. In (B),
eraging over azimuthal angles. the total luminosity Ltot (black) is the sum of the
1
Jet Propulsion Laboratory, California Institute of Technology, The system was evolved until the central stellar luminosity L* (red) and accretion luminosity
Pasadena, CA 91109, USA. 2Department of Physics, Kyoto Uni- particle number density reached 1012 cm−3. We
versity, Kyoto 606-8502, Japan. 3Institute for the Physics and Lacc (blue). The KH time scale tKH (red) and accre-
Mathematics of the Universe, Todai Institutes for Advanced then introduced a sink cell of size ≅10 astro- tion time scale tacc (blue) are depicted in (C). The
Study, University of Tokyo, Kashiwa, Chiba 277-8568, Japan. nomical units (AU) and followed the subsequent yellow and blue backgrounds denote the adiabatic
*To whom correspondence should be addressed. E-mail: evolution of the central protostar with a stellar accretion phase and KH contraction phase in the
hosokwtk@gmail.com evolution code. The accretion rate onto the pro- protostellar evolution.
1250 2 DECEMBER 2011 VOL 334 SCIENCE www.sciencemag.org
3. REPORTS
three-body reactions. The molecular disk ex- In the early accretion phase, the stellar radi- (UV) flux rapidly rose (Fig. 1D). Thus, ionization
tended out to ≅400 AU from the protostar, when us remained almost constant at ≅50 solar radius and heating by UV photons became important
the stellar mass was 10 M⊙. Accretion onto the (R⊙) (Fig. 1A). The stellar luminosity was sub- already in the KH contraction stage.
protostar proceeded through this molecular disk stantially lower than the accretion luminosity When the stellar mass was 20 M⊙, an ionized
as angular momentum was transported outward. (Fig. 1B), and the KH time scale was much longer region rapidly expanded in a bipolar shape per-
The accretion rate onto the protostar was ≅1.6 × than the accretion time (Fig. 1C). Consequent- pendicular to the disk, where gas was cleared
10−3 M⊙ year−1 at that moment. ly, entropy carried by the accreted gas accumu- away (Fig. 2A). At this moment, the disk ex-
The evolution of the central protostar is de- lated at the stellar surface nearly without loss. tended out to ≅600 AU. The disk was self-shielded
termined by competition between mass growth During this quasi-adiabatic stage (M* < 7 M⊙), against the stellar H2-dissociating (11.2 eV ≤ hν ≤
by accretion and radiative energy loss from the the luminosity L* increased with stellar mass. 13.6 eV) as well as the ionizing radiation. The
stellar interior. The time scale for the former When the star grew to 8 M⊙, the KH time scale ionized atomic hydrogen (H II) region continued
˙
is the accretion time scale tacc ≡ M*/M , where finally fell below the accretion time scale (Fig. to grow and finally broke out of the accreting
˙
M* is the mass of the protostar and M is the 1C). After this, the protostar began its so-called envelope. At M* ≅ 25 M⊙, the size of the bipolar
mass accretion rate, whereas that for the latter KH contraction, in which it gradually contracted H II region exceeded 0.1 pc (Fig. 2B). Because
is the Kelvin-Helmholtz (KH) time scale tKH ≡ as it radiated its energy away (Fig. 1A). The stel- of the high pressure of the heated ionized gas,
G M*2/R*L*, where L* is the luminosity from lar luminosity was the main component of the the opening angle of the ionized region also
the stellar interior, R* is the radius of the pro- total luminosity after this evolutionary stage (Fig. increased as the star grew (Fig. 2C). Shocks
tostar, and G is the gravitational constant. The 1B). The stellar luminosity L* increased, and propagated into the envelope preceding the ex-
Downloaded from www.sciencemag.org on December 1, 2011
total luminosity of the protostar Ltot is the sum stellar radius R* decreased, as the stellar mass pansion of the ionized region. The shocked gas
of the stellar luminosity L* and accretion lumi- increased. As a result, the stellar effective tem- was accelerated outward at a velocity of several
˙
nosity Lacc ≡ GM*M/R* (13). perature Teff º (L*/R*2)1/4 and the ultraviolet kilometers per second. The shock even reached
regions shielded against direct stellar UV irra-
diation. The outflowing gas stopped the infall
of material from the envelope onto the disk (fig.
S7). Without the replenishment of disk mate-
rial from the envelope, the accretion rate onto
the protostar decreased (Fig. 3). In addition,
the absence of accreting material onto the cir-
cumstellar disk means that the disk was ex-
posed to the intense ionizing radiation from
the star. The resulting photoevaporation of disk
gas also reduced the accretion rate onto the
protostar. The photoevaporated gas escaped to-
ward the polar direction within the ionized re-
gion. The typical velocity of the flow was several
tens of kilometers per second, comparable with
the sound speed of the ionized gas, which was
high enough for the evaporating flow to escape
from the gravitational potential well of the dark
matter halo.
When central nuclear hydrogen burning first
commenced at a stellar mass of 35 M⊙, it was via
the proton-proton (pp)–chain normally associ-
ated with low-mass stars. The primordial mate-
rial does not have the nuclear catalysts necessary
for carbon–nitrogen–oxygen (CNO)–cycle hy-
drogen burning. Because the pp-chain alone can-
not produce nuclear energy at the rate necessary
to cover the radiative energy loss from the stel-
lar surface, the star continues to contract until
central temperatures and densities attain values
that enable the 3-a process of helium burning
(11). The product of helium burning is carbon,
and once the relative mass abundance of carbon
reaches ∼10−12, CNO-cycle hydrogen burning
takes over as the principal source of nuclear en-
ergy production, albeit at much higher central
densities and temperatures than those of stars
with solar abundances. These first-generation
ZAMS (zero-age main sequence) stars are thus
Fig. 2. UV radiative feedback from the primordial protostar. The spatial distributions of gas temper- more compact and hotter than are their present-
ature (left), number density (right), and velocity (right, arrows) are presented in each panel for the central day counterparts of equal mass (14). The subse-
regions of the computational domain. The four panels show snapshots at times when the stellar mass quent evolution of the accreting star followed
is M* = 20 M⊙ (A), 25 M⊙ (B), 35 M⊙ (C), and 42 M⊙ (D). The elapsed time since the birth of the along the ZAMS mass-radius relationship (Fig.
primordial protostar is labeled in each panel. 1A). By the time the star attained 40 M⊙, the
www.sciencemag.org SCIENCE VOL 334 2 DECEMBER 2011 1251
4. REPORTS
Fig. 3. Evolution of the 0.01 stantially. Thus, our radiation-hydrodynamic cal-
accretion rate onto the pri- culations predict final masses systematically lower
Acc. Rate: M ( M / yr )
mordial protostar. The blue than those of the semianalytic models.
line indicates the evolu- Although the results described above provide
tion, which includes the a complete picture of how a primordial protostar
effect of UV radiative feed- 0.001
No feedback regulates and terminates its growth, there are a
back from the protostar. (a) few key quantities that determine the strength of
The red line indicates a nu- (b) the feedback effect, as suggested by the semi-
merical experiment with (c)
analytic model (8). With smaller initial rotation
no UV feedback. The open of the natal dense core, the density in the en-
and solid circles denote 1e-4 (d)
velope near the polar directions would be higher.
the characteristic epochs feedback Hydrogen recombination occurs rapidly in the
of the protostellar evolu-
dense gas, which prevents the breakout of the
tion, beginning of the KH
contraction, and the pro- 0 10 20 30 40 50 60 ionized region. Gas accretion can last for a longer
tostar’s arrival to the ZAMS. time in this case and would form more massive
Stellar Mass: M ( M )
Fig. 2, A to D, shows the stars (SOM text). Nevertheless, even considering
snapshots at the moments marked here with asterisks. variations among dark halos bearing the first
stars, a substantial fraction of the first stars should
Downloaded from www.sciencemag.org on December 1, 2011
be less massive than 100 M⊙ and end their lives
as ordinary core-collapse supernovae. Gas ac-
entire region above and below the disk (Fig. 2D) than the first stars because of a different gas ther- cretion might not be completely halted in a few
was ionized. Mass accretion was terminated when mal evolution, with additional radiative cooling exceptional cases, thus leading to the formation
the stellar mass was 43 M⊙ (Fig. 3). via H2 and HD molecules (21, 22). However, this of a small number of extremely massive stars
The entire evolution described above took mode of star formation is suppressed even with that are >100 M⊙ in the early universe (26). Black
about 0.1 million years from the birth of the em- weak H2 photodissociating background radia- holes left after such very massive stars’ deaths
bryo protostar to the termination of the accretion. tion (22). If so suppressed, the formation process might have grown up to be the supermassive
The star is expected to live another few million of the later-generation primordial stars would black holes lying in galaxies.
years before exhausting all available nuclear fuel be similar to that of the very first stars, and most Recent 3D cosmological simulations showed
and exploding as a core-collapse supernova (15). primordial stars could have experienced the evo- that a primordial gas cloud breaks up into several
Our calculations show that the first stars reg- lution presented in this article regardless of their embryo protostars in an early phase (27, 28).
ulated their growth by their own radiation. They generations. One might argue that today’s ob- Each of these protostars would continue to grow
were not extremely massive, but rather similar in served metal-deficient stars formed after an epi- through mass accretion, but it remained uncertain
mass to the O-type stars in our Galaxy. This re- sode of star formation with nonzero metallicity. how and when the growth is halted. Our radiation-
solves a long-standing enigma regarding the el- For the star formation process to differ substan- hydrodynamics calculations explicitly show that
emental abundance patterns of the Galactic oldest tially from that of the very first stars, one would the parent gas cloud is evaporated by intense
metal-poor stars, which contain nucleosynthetic require metallicities in excess of [Fe/H] > −5 radiation from the central star when its mass is
signatures from the earliest generation of stars. (23, 24). Caffau and co-workers (25) report on ob- several tens of solar masses. The circumstellar
If a substantial number of first stars had masses servations of a metal-deficient star with [Fe/H] ≅ disks in our simulations are marginally stable
in excess of 100 M⊙, they would end their lives −5, but without the corresponding enhancement against gravitational fragmentation (fig. S5). We
through pair-instability supernovae (16, 17), ex- of carbon, nitrogen, and oxygen found in metal- expect that these disks—in a 3D simulation—
pelling heavy elements that would imprint a deficient stars. The abundance pattern of this star would evolve analogously to our numerical sim-
characteristic nucleosynthetic signature to the agrees with expectations from core-collapse su- ulations with assumed axial symmetry and have a
elemental abundances in metal-poor stars. How- pernovae, implying that it formed from gas en- similar time-averaged structure. It is conceivable
ever, no such signatures have been detected in hanced by material ejected from primordial stars that a few protostars are ejected dynamically
the metal-poor stars in the Galactic halo (18, 19). with masses less than 100 M⊙. from the parent cloud, to remain as low-mass
For example, the abundances of elements with We have performed radiation-hydrodynamic stars. Observationally, however, there have been
odd atomic numbers are generally reduced in simulations only for a single star-forming region no low-mass zero-metallicity stars discovered in
remnants of primordial supernovae. The odd- embedded in a cosmological simulation. Our se- the Galaxy. This fact suggests the limited for-
even contrast pattern expected in pair-instability lected dark halo was typical in mass, spin, and mation efficiency of such low-mass primordial
supernovae is much stronger than the observed formation epoch when compared with those in stars (19). Low-mass stars (<1 M⊙) and extreme-
patterns in Galactic metal-poor stars (17). More- other studies (5). The evolution presented here is ly high mass stars (>100 M⊙), if any, are thus a
over, pair-instability supernovae predict a small somewhat similar to that predicted by the semi- minor population among the first stars.
abundance ratio [Zn/Fe], but observed values are analytic model, in which the expansion of the Our self-consistent calculations show that
much larger (16). Detailed spectroscopic studies ionized region begins when the stellar mass is the characteristic mass of the first stars is several
of extremely metal-deficient stars indicate that ≅25 M⊙ and the final mass is ≅57 M⊙ (8), the tens of solar masses. Although this is less than
the metal-poor stars were born in an interstellar lowest final stellar mass predicted by the semi- that of the conventionally proclaimed extremely
medium that had been metal-enriched by super- analytic treatment. If input parameters of the massive stars (>100 M⊙), it is still much larger
novae of ordinary massive stars (20). semianalytic models are chosen to fit our initial than the characteristic mass of stars in our galaxy
Second-generation stars, which formed from gas cloud, however, the final mass should be (<1 M⊙) (29).
the primordial gas affected by radiative or me- higher, ≅90 M⊙ (SOM text). Our calculations fol-
chanical feedback from the first stars, could have low the dynamical response of the infalling gas References and Notes
dominated the metallicity of the young inter- onto the circumstellar disk. The expansion of 1. V. Bromm, N. Yoshida, L. Hernquist, C. F. McKee, Nature
459, 49 (2009).
stellar medium, which then spawned the observed the ionized region around the protostar generates 2. K. Omukai, R. Nishi, Astrophys. J. 508, 141 (1998).
Galactic halo stars. These second-generation stars a powerful outflow even behind the surrounding 3. T. Abel, G. L. Bryan, M. L. Norman, Science 295, 93
could have been more numerous but less massive disk. This effect reduces the accretion rate sub- (2002).
1252 2 DECEMBER 2011 VOL 334 SCIENCE www.sciencemag.org
5. REPORTS
4. N. Yoshida, K. Omukai, L. Hernquist, T. Abel, Astrophys. J. 19. A. Frebel, J. L. Johnson, V. Bromm, Mon. Not. R. Astron. manuscript. T.H. appreciates the support by Fellowship
652, 6 (2006). Soc. 392, L50 (2009). of the Japan Society for the Promotion of Science for
5. B. W. O’Shea, M. L. Norman, Astrophys. J. 654, 66 20. N. Iwamoto, H. Umeda, N. Tominaga, K. Nomoto, K. Maeda, Research Abroad. The present work is supported in part by
(2007). Science 309, 451 (2005). the grants-in-aid by the Ministry of Education, Science and
6. N. Yoshida, K. Omukai, L. Hernquist, Science 321, 669 21. B. W. O'Shea, T. Abel, D. Whalen, M. L. Norman, Culture of Japan (19047004, 2168407, 21244021:KO,
(2008). Astrophys. J. 628, L5 (2005). 20674003:NY). Portions of this research were conducted at
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Materials and Methods
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Downloaded from www.sciencemag.org on December 1, 2011
of two counter-oscillating sublattices within the
Entangling Macroscopic Diamonds diamond structure. The optical phonons are mac-
roscopic, persistent excitations distributed over
at Room Temperature ∼1016 atoms within the crystals. The phonons have
a very high carrier frequency of 40 THz owing
K. C. Lee,1* M. R. Sprague,1* B. J. Sussman,2 J. Nunn,1 N. K. Langford,1 X.-M. Jin,1,3 to the extremely strong interactions between neigh-
T. Champion,1 P. Michelberger,1 K. F. Reim,1 D. England,1 D. Jaksch,1,3 I. A. Walmsley1† boring atoms, giving rise to a mechanically stiff
lattice. This large energy, compatible with the ul-
Quantum entanglement in the motion of macroscopic solid bodies has implications both for trashort pulses in our experiment (bandwidth
quantum technologies and foundational studies of the boundary between the quantum and ∼7 THz), also eliminates the need for cooling or
classical worlds. Entanglement is usually fragile in room-temperature solids, owing to strong optical pumping, because thermal excitations are
interactions both internally and with the noisy environment. We generated motional entanglement negligible at room temperature. The specific ex-
between vibrational states of two spatially separated, millimeter-sized diamonds at room perimental protocol that we use is based on the
temperature. By measuring strong nonclassical correlations between Raman-scattered photons, well-known DLCZ scheme (12) and previous
we showed that the quantum state of the diamonds has positive concurrence with 98% probability. pioneering experiments in cold atomic ensem-
Our results show that entanglement can persist in the classical context of moving macroscopic bles (13–16). We first create a phonon via spon-
solids in ambient conditions. taneous Raman scattering from a strong optical
pump pulse, an event that is simultaneously ac-
ur intuition about the nature of the phys- approach is to design systems with well-defined companied by the emission of a Stokes photon
O ical world is strongly conditioned by
the experience that macroscopic solids
move according to the rules of classical mechan-
and long-lived normal modes that can be selec-
tively excited, and then to cool them to remove
thermal noise and isolate them from the environ-
(red-shifted from the pump). After this interac-
tion, the joint state of the diamond and the
Stokes mode can be written as
ics. Quantum theory, however, asserts that super- ment. Substantial progress has been made toward  Ã
positions and entanglement are possible even for demonstrating strong quantum signatures in larger ys ≈ 1 þ es s† (ts )b† (ts ) vac ð1Þ
large objects. Therefore, exploration of the persist- systems—for example, in optomechanical (3–5),
ence of quantum correlations in the traditionally molecular (6), and superconducting (7) systems. where |es|2 1 is the scattering probability
classical realm is important for both fundamental Mechanical oscillators can now be cooled to the and |vac〉 = |vacopt〉 ⊗ |vacvib〉 is the joint op-
science and technology, because of the impli- thermal ground state (7–9). tical and vibrational vacuum state containing
cations for physics beyond conventional quan- A different approach is required, however, no photons and no phonons; s and b are the
tum mechanics (1) and for quantum information to reveal quantum features in the motion of “or- bosonic annihilation operators for the Stokes
processing, which requires sustained coherence dinary” solids in the high-entropy environment and phonon modes, respectively, evaluated at
across many particles (2). present at ambient conditions. Without a spe- the time ts when the pump pulse exits the dia-
The two main barriers for creating superpo- cially engineered system, measurements must be mond. Equation 1 describes an entangled state
sitions and entanglement in the mechanical mo- made on time scales shorter than the character- of optical and material modes, which is already
tion of macroscopic systems are strong internal istically fast coherence decay times of a real-world nonclassical. To entangle two diamonds, we simul-
interactions, which complicate the dynamics, and system. This can be achieved with ultrashort op- taneously pump two separate crystals—producing
strong coupling with the environment, which tical pulses. Recent studies of quantum coherence the state |Ys〉 = |ysL〉|ysR〉, where L and R denote
leads to short decoherence times. The standard in biology have used ultrafast probes and inter- the left and right diamonds, respectively—and
ference measurements to establish the persist- we combine their Stokes modes on a polarizing
1
Clarendon Laboratory, University of Oxford, Parks Road, Oxford ence of quantum behavior in naturally occurring beamsplitter (Fig. 1). The Stokes modes are caused
OX1 3PU, UK. 2National Research Council of Canada, Ottawa, bulk systems (10, 11). To probe entanglement, to interfere with relative phase ϕs by means of a
Ontario K1A 0R6, Canada. 3Centre for Quantum Technologies,
National University of Singapore, Singapore. however, it is also necessary to access the cor- half-wave plate and polarizer. Detection of a
*These authors contributed equally to this work.
relations of the excited modes. Stokes photon at a detector Ds placed behind
†To whom correspondence should be addressed. E-mail: We study excitations of the optical phonon the polarizer corresponds to application of the
walmsley@physics.ox.ac.uk mode in diamond, a bulk vibration consisting measurement (17) E = 〈vacopt|s(t′s), where t′s is
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