A possible carbonrich_interior_in_superearth_55_cancrieSérgio Sacani
1) The document analyzes the possibility that the interior of the super-Earth exoplanet 55 Cancri e could be carbon-rich rather than oxygen-rich.
2) Models that assume an oxygen-rich interior with iron, silicates, and a water envelope cannot fully explain 55 Cancri e's mass and radius measurements. However, a carbon-rich interior containing iron, silicon carbide, and/or carbon could explain the observations without needing a volatile envelope.
3) A carbon-rich interior for 55 Cancri e is plausible given the reported carbon-rich composition of its host star, though more data is needed on the star's elemental abundances and the planet's atmosphere.
The 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 experiments on samples containing olivine, chromite, and mid-ocean ridge basalt conducted at high pressures and temperatures to study the stability of melt-rich channels in Earth's mantle. The experiments involved deforming the samples using torsion and then annealing them at static conditions while observing any melt-rich bands under a scanning electron microscope. The results showed melt-rich bands remained even after 10 hours of annealing, suggesting the driving force for melt segregation is stronger than the dissipation force in the mantle, with surface tension playing a larger role on planetary objects with lower gravity than Earth.
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.
1) The Fermi bubbles are giant gamma-ray emitting structures extending above and below the galactic center.
2) The bubbles may have been formed by periodic capture of stars by the supermassive black hole at the galactic center, releasing energy of around 3x10^52 ergs per capture.
3) This energy injection could produce very hot plasma, accelerating electrons that produce radio and gamma-ray emission through synchrotron radiation and inverse Compton scattering.
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.
The exceptional soft_x_ray_halo_of_the_galaxy_merger_ngc6240Sérgio Sacani
The document summarizes a recent 150-ks Chandra observation of the galaxy merger NGC 6240. Extended soft X-ray emission is detected over a 110x80 kpc region around NGC 6240. Spectral analysis finds the emission comes from hot gas with a temperature of around 7.5 million K and a total mass of about 10^10 solar masses. The gas properties suggest widespread star formation over the past 200 Myr rather than a recent nuclear starburst. The fate of the diffuse hot gas after the galaxy merger is uncertain but it may be retained and evolve into the halo of an elliptical galaxy.
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.
A possible carbonrich_interior_in_superearth_55_cancrieSérgio Sacani
1) The document analyzes the possibility that the interior of the super-Earth exoplanet 55 Cancri e could be carbon-rich rather than oxygen-rich.
2) Models that assume an oxygen-rich interior with iron, silicates, and a water envelope cannot fully explain 55 Cancri e's mass and radius measurements. However, a carbon-rich interior containing iron, silicon carbide, and/or carbon could explain the observations without needing a volatile envelope.
3) A carbon-rich interior for 55 Cancri e is plausible given the reported carbon-rich composition of its host star, though more data is needed on the star's elemental abundances and the planet's atmosphere.
The 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 experiments on samples containing olivine, chromite, and mid-ocean ridge basalt conducted at high pressures and temperatures to study the stability of melt-rich channels in Earth's mantle. The experiments involved deforming the samples using torsion and then annealing them at static conditions while observing any melt-rich bands under a scanning electron microscope. The results showed melt-rich bands remained even after 10 hours of annealing, suggesting the driving force for melt segregation is stronger than the dissipation force in the mantle, with surface tension playing a larger role on planetary objects with lower gravity than Earth.
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.
1) The Fermi bubbles are giant gamma-ray emitting structures extending above and below the galactic center.
2) The bubbles may have been formed by periodic capture of stars by the supermassive black hole at the galactic center, releasing energy of around 3x10^52 ergs per capture.
3) This energy injection could produce very hot plasma, accelerating electrons that produce radio and gamma-ray emission through synchrotron radiation and inverse Compton scattering.
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.
The exceptional soft_x_ray_halo_of_the_galaxy_merger_ngc6240Sérgio Sacani
The document summarizes a recent 150-ks Chandra observation of the galaxy merger NGC 6240. Extended soft X-ray emission is detected over a 110x80 kpc region around NGC 6240. Spectral analysis finds the emission comes from hot gas with a temperature of around 7.5 million K and a total mass of about 10^10 solar masses. The gas properties suggest widespread star formation over the past 200 Myr rather than a recent nuclear starburst. The fate of the diffuse hot gas after the galaxy merger is uncertain but it may be retained and evolve into the halo of an elliptical galaxy.
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.
This document presents an overview of space plasma physics, specifically magnetic storms and substorms. It provides basic definitions and examples to educate those unfamiliar or rusty with the science. The outline includes sections on storm and substorm basics, examples with analysis, and data collected from satellites. Magnetic storms occur over weeks/months when particles enhance the ring current. Substorms happen over hours in growth, onset/expansion, and recovery phases, seen through auroral observations and particle densities. Examples of data include images, magnetic and electric fields, and particle fluxes.
Introduction to electromagnetic exploration methodoilandgas24
1. Electromagnetic methods measure the electrical resistivity of the Earth using electromagnetic induction rather than direct contact. This allows data to be collected from moving platforms like helicopters.
2. When EM signals enter the Earth, they can propagate as waves in low conductivity environments or diffuse in higher conductivity environments. Diffusion causes the signal amplitude to decrease exponentially with distance.
3. EM methods work by a transmitter generating a primary oscillating magnetic field that induces currents in conductors, which generate a secondary magnetic field measured by a receiver to obtain information about conductors.
The palaeomagnetism of glauconitic sedimentsJohn Smith
The palaeoenvironmental significance of glaucony has long been appreciated, but accurate palaeomagnetic dating of events recorded by glauconitic horizons requires an understanding of how glauconitic sediments acquire a remanent magnetization. Pure glauconitic minerals are paramagnetic, but glauconite grains are large and slow-forming (over periods that can exceed 100 kyr), with complex and variable morphologies. It is, thus, possible that small magnetic grains within glaucony particles may carry a significant fraction of the remanence in weakly magnetized sediments. Any remanence carried by glauconitic grains may therefore represent the geomagnetic field at a time significantly later than the time of deposition, or a time-averaged signal over some or all of the formation period. We investigated this problem using weakly magnetic Palaeocene glauconitic siltstones from southern New Zealand. We disaggregated the rock and separated it magnetically into glauconitic and non-glauconitic fractions. Results from stepwise isothermal remanent magnetization (IRM) acquisition, alternating-field demagnetization, temperature dependence of magnetic susceptibility, and stepwise thermal demagnetization of a triaxial IRM were used to demonstrate that the remanent magnetization is carried by single-domain or pseudo-single-domain magnetite in the non-glauconitic sediment fraction, and that the glauconite grains themselves make no contribution to the remanent magnetization. However, accurate measurement of the primary remanence is complicated by a strong viscous overprint and mineral alteration during thermal demagnetization studies. Identification of magnetite as the remanence carrier in sediments within a reducing diagenetic environment gives confidence that the remanence has a depositional origin. Glauconite does not carry a remanence; therefore, its effect is to dilute and weaken the overall magnetization. Furthermore, the use of rock magnetic parameters may be problematic when glauconite concentrations are (as in the studied sediments) orders of magnitude greater than remanence carrier concentrations, because in such cases the glauconite susceptibility can dominate that of the remanence carriers.
An airborne electromagnetic survey uses aircraft-mounted electromagnetic coils to map variations in ground conductivity. This non-invasive technique can identify metallic conductors like massive sulfides over large areas rapidly and at low cost. Factors like signal-to-noise ratio, penetration depth, discrimination of conductor types, and lateral coverage determine what conductors can be detected. Applications include mineral exploration, environmental mapping, hydrocarbon and groundwater exploration. Survey data is presented as profiles, apparent resistivity maps, and interpretation maps identifying anomaly locations and modeling their conductivity-thickness. Airborne EM has advantages over ground methods in accessing remote areas and efficiently locating targets for follow-up.
The document summarizes the Van Allen radiation belts, which are zones of high-energy particles trapped by Earth's magnetic field. There are two main belts - an inner belt containing high-energy protons and an outer belt containing electrons. Occasionally a third temporary belt can form. The particles can damage satellites and electronics, posing challenges for space exploration. NASA's Van Allen Probes mission studied the dynamics and variability of the belts, discovering phenomena like "whistler mode" waves that produce audible noises. Potential strategies to clear the belts are discussed, but the long-term effects are uncertain.
This document summarizes the history of cosmic ray research from the early 1900s to present day. It describes key early experiments measuring ionization at different altitudes that helped establish cosmic rays originate outside Earth's atmosphere. It then discusses subsequent discoveries like pions, muons and air shower cascades. The document outlines current understanding of cosmic ray sources and composition. It also explains energy loss mechanisms and interactions of cosmic rays in the atmosphere that produce air showers of particles detected at Earth's surface.
A supernova is an explosion of a massive supergiant star that may shine with the brightness of 10 billion suns. Supernovae are classified as Type I or Type II depending on their light curves and spectra. Type I supernovae exhibit sharp maxima that decay gradually and lack hydrogen, while Type II have less sharp peaks, decay more sharply, and contain hydrogen. Type Ia supernovae, specifically, have become important for measuring cosmological distances due to their reliable peak brightness.
A propable milli_parsec_supermassive_binary_black_hole_in_the_nearest_quasar_...Sérgio Sacani
Astrônomos usando o Telescópio Espacial Hubble da NASA descobriram que a Markarian 231 (Mrk 231), a galáxia mais próxima da Terra que abriga um quasar, é alimentada por dois buracos negros centrais girando violentamente um em relação ao outro.
A descoberta sugere que os quasares, os brilhantes núcleos das galáxias ativas, podem normalmente abrigar dois buracos negros centrais que caem, um na órbita do outro como resultado da fusão de duas galáxias. Como um par de patinadores, o buraco negro duplo gera uma tremenda quantidade de energia que faz o núcleo da galáxia que o abriga se sobrepor ao brilho da população de bilhões de estrelas da galáxia, que os cientistas então identificam como quasares.
Os cientistas procuraram nas observações de arquivo do Hubble feitas na radiação ultravioleta emitida do centro da Mrk 231 para descobrir o que eles descrevem como propriedades extremas e surpreendentes.
Evidence for a_complex_enrichment_history_of_the_stream_from_fairall_9_sightlineSérgio Sacani
This study analyzes absorption spectra of the Magellanic Stream (MS) toward the quasar Fairall 9, obtained using the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) and the Very Large Telescope Ultraviolet and Visible Echelle Spectrograph (VLT/UVES). The spectra reveal absorption from multiple velocity components of the MS, indicating multiphase gas. Surprisingly, the sulfur abundance is found to be high ([S/H] = -0.30), five times higher than other MS sightlines, while the nitrogen abundance is lower ([N/H] = -1.15). This points to a complex enrichment history, where the gas toward Fair
Graphical 3D Modeling of Molecules and Nanostructures in Sub-nanometer Scale ...Stoyan Sarg Sargoytchev
The Basic Structures of Matter – Supergravitation Unified Theory (BSM-SG) reveals non-spherical shapes of the stable elementary particles, composed of two types of helical structures with opposite twisting. Proton and neutron have one and the same toroidal sub-structure, but the shape of proton is a twisted torus like the figure 8, while the neutron is a double folded. The shape of proton permits modulation of the space fabrics creating a positive E-field. At neutron such modulation is locked in the near field, so it is not detectable, but when in motion it creates a magnetic field. Due to it’s near E-field the neutron is stable over the proton, forming a deuteron. The electron is a different three body system with two intrinsic frequencies. Its structure and dynamic properties provide classical explanations of: Compton frequency, anomalous magnetic moment, spin and relativistic effect of mass increase. The near Coulomb field of the proton defines the trace of orbiting electron. The atomic nuclei are 3D compositions of protons and neutrons, kept by the attractive supergravitational forces, while balancing the repulsive forces between protons. The increase of number of protons reveals the build-up trend of the atomic nuclei showing a perfect match with the pattern of the Periodic Table. The features defining the valences and the angular restrictions of the chemical bonds are apparent. The rotational freedom of neutrons over protons is behind the nuclear magnetic moment. The BSM-SG atomic models are convenient for 3D graphical modeling of complex molecules and nanostructures with sub-nanometer resolution.
The magnetic method detects near-surface ferrous materials by measuring anomalies in the Earth's magnetic field. When ferrous objects are placed in the magnetic field, they develop an induced magnetic field that is superimposed on the Earth's field, creating a detectable anomaly. The method works best for detecting buried ferrous metals and can be used to map geology and locate buried infrastructure through magnetic susceptibility variations in rocks.
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
This document summarizes the differentiation of the Earth. It discusses how the Earth initially formed as a molten mass and over time separated into layers with the heavier materials sinking to the center to form the core. The two main theories for this differentiation are homogeneous and heterogeneous accretion. Evidence from the Moon supports the Earth differentiating into layers early in its formation history around 4.5 billion years ago. The Earth is now composed of concentric layers that decrease in density from the iron-nickel core, to the silicate mantle, and finally the crust at the surface.
1) Geophysical surveys have been using measurements of the Earth's magnetic field for nearly 500 years since Gilbert showed that the Earth behaves like a large magnet.
2) Gravity and magnetic surveying methods are similar in that they both measure naturally occurring fields (potential fields), can use identical physical representations like magnetic monopoles, and have similar data acquisition and interpretation.
3) However, magnetic surveying also has differences from gravity - magnetic susceptibility of rocks can vary more than density, magnetism can be attractive or repulsive unlike gravity, magnetic sources always occur in pairs unlike gravity, and the magnetic field is time-dependent unlike gravity.
This document summarizes observations of the W49 giant molecular cloud (GMC) using the PMO 14m telescope and the Submillimeter Array (SMA). The PMO observations mapped the entire GMC in various molecular lines at scales up to 113 pc, while the SMA mosaic mapped the central star-forming region W49N at scales down to 0.5 pc. The observations are used to derive the mass structure of the GMC across all scales. The main findings are that the W49 GMC has a total gas mass of 1.1 million solar masses within 60 pc and 2x10^5 solar masses within 6 pc. The mass is distributed in a hierarchical network of filaments converging toward the central
Revealing the invisible universe from MaunakeaILOAHawaii
This document discusses submillimeter astronomy and the importance of Maunakea, Hawaii as a location for observing submillimeter wavelengths. It summarizes that submillimeter radiation reveals the earliest moments of star and galaxy formation, but this wavelength is blocked by Earth's atmosphere and can only be observed from a few locations worldwide, including Maunakea. The James Clerk Maxwell Telescope and its SCUBA camera made early discoveries in this field, and ongoing surveys continue to reveal new phenomena like the brightest stellar flare ever recorded in submillimeter wavelengths. The document also discusses the Event Horizon Telescope and its goal of directly imaging a black hole by observing in millimeter and submillimeter wavelengths where a black hole's event
The document repeats the phrase "1971Moon....3....3H" over 100 times. It appears to be referring to the year 1971 and the moon, but provides no other context or information.
The document summarizes observations of the unusual gamma-ray burst GRB 101225A. Key points:
- GRB 101225A had exceptionally long-lived gamma-ray emission and a subsequent bright X-ray transient with a hot thermal component.
- The optical emission over the first 10 days evolved as an expanding, cooling blackbody. An additional supernova component then emerged.
- The redshift is estimated to be 0.33 based on fitting the spectral energy distribution and light curve with a GRB-supernova template.
- The proposed progenitor is a merger of a helium star and neutron star that underwent a common envelope phase, expelling its hydrogen envelope. The explosion created a
This document presents an overview of space plasma physics, specifically magnetic storms and substorms. It provides basic definitions and examples to educate those unfamiliar or rusty with the science. The outline includes sections on storm and substorm basics, examples with analysis, and data collected from satellites. Magnetic storms occur over weeks/months when particles enhance the ring current. Substorms happen over hours in growth, onset/expansion, and recovery phases, seen through auroral observations and particle densities. Examples of data include images, magnetic and electric fields, and particle fluxes.
Introduction to electromagnetic exploration methodoilandgas24
1. Electromagnetic methods measure the electrical resistivity of the Earth using electromagnetic induction rather than direct contact. This allows data to be collected from moving platforms like helicopters.
2. When EM signals enter the Earth, they can propagate as waves in low conductivity environments or diffuse in higher conductivity environments. Diffusion causes the signal amplitude to decrease exponentially with distance.
3. EM methods work by a transmitter generating a primary oscillating magnetic field that induces currents in conductors, which generate a secondary magnetic field measured by a receiver to obtain information about conductors.
The palaeomagnetism of glauconitic sedimentsJohn Smith
The palaeoenvironmental significance of glaucony has long been appreciated, but accurate palaeomagnetic dating of events recorded by glauconitic horizons requires an understanding of how glauconitic sediments acquire a remanent magnetization. Pure glauconitic minerals are paramagnetic, but glauconite grains are large and slow-forming (over periods that can exceed 100 kyr), with complex and variable morphologies. It is, thus, possible that small magnetic grains within glaucony particles may carry a significant fraction of the remanence in weakly magnetized sediments. Any remanence carried by glauconitic grains may therefore represent the geomagnetic field at a time significantly later than the time of deposition, or a time-averaged signal over some or all of the formation period. We investigated this problem using weakly magnetic Palaeocene glauconitic siltstones from southern New Zealand. We disaggregated the rock and separated it magnetically into glauconitic and non-glauconitic fractions. Results from stepwise isothermal remanent magnetization (IRM) acquisition, alternating-field demagnetization, temperature dependence of magnetic susceptibility, and stepwise thermal demagnetization of a triaxial IRM were used to demonstrate that the remanent magnetization is carried by single-domain or pseudo-single-domain magnetite in the non-glauconitic sediment fraction, and that the glauconite grains themselves make no contribution to the remanent magnetization. However, accurate measurement of the primary remanence is complicated by a strong viscous overprint and mineral alteration during thermal demagnetization studies. Identification of magnetite as the remanence carrier in sediments within a reducing diagenetic environment gives confidence that the remanence has a depositional origin. Glauconite does not carry a remanence; therefore, its effect is to dilute and weaken the overall magnetization. Furthermore, the use of rock magnetic parameters may be problematic when glauconite concentrations are (as in the studied sediments) orders of magnitude greater than remanence carrier concentrations, because in such cases the glauconite susceptibility can dominate that of the remanence carriers.
An airborne electromagnetic survey uses aircraft-mounted electromagnetic coils to map variations in ground conductivity. This non-invasive technique can identify metallic conductors like massive sulfides over large areas rapidly and at low cost. Factors like signal-to-noise ratio, penetration depth, discrimination of conductor types, and lateral coverage determine what conductors can be detected. Applications include mineral exploration, environmental mapping, hydrocarbon and groundwater exploration. Survey data is presented as profiles, apparent resistivity maps, and interpretation maps identifying anomaly locations and modeling their conductivity-thickness. Airborne EM has advantages over ground methods in accessing remote areas and efficiently locating targets for follow-up.
The document summarizes the Van Allen radiation belts, which are zones of high-energy particles trapped by Earth's magnetic field. There are two main belts - an inner belt containing high-energy protons and an outer belt containing electrons. Occasionally a third temporary belt can form. The particles can damage satellites and electronics, posing challenges for space exploration. NASA's Van Allen Probes mission studied the dynamics and variability of the belts, discovering phenomena like "whistler mode" waves that produce audible noises. Potential strategies to clear the belts are discussed, but the long-term effects are uncertain.
This document summarizes the history of cosmic ray research from the early 1900s to present day. It describes key early experiments measuring ionization at different altitudes that helped establish cosmic rays originate outside Earth's atmosphere. It then discusses subsequent discoveries like pions, muons and air shower cascades. The document outlines current understanding of cosmic ray sources and composition. It also explains energy loss mechanisms and interactions of cosmic rays in the atmosphere that produce air showers of particles detected at Earth's surface.
A supernova is an explosion of a massive supergiant star that may shine with the brightness of 10 billion suns. Supernovae are classified as Type I or Type II depending on their light curves and spectra. Type I supernovae exhibit sharp maxima that decay gradually and lack hydrogen, while Type II have less sharp peaks, decay more sharply, and contain hydrogen. Type Ia supernovae, specifically, have become important for measuring cosmological distances due to their reliable peak brightness.
A propable milli_parsec_supermassive_binary_black_hole_in_the_nearest_quasar_...Sérgio Sacani
Astrônomos usando o Telescópio Espacial Hubble da NASA descobriram que a Markarian 231 (Mrk 231), a galáxia mais próxima da Terra que abriga um quasar, é alimentada por dois buracos negros centrais girando violentamente um em relação ao outro.
A descoberta sugere que os quasares, os brilhantes núcleos das galáxias ativas, podem normalmente abrigar dois buracos negros centrais que caem, um na órbita do outro como resultado da fusão de duas galáxias. Como um par de patinadores, o buraco negro duplo gera uma tremenda quantidade de energia que faz o núcleo da galáxia que o abriga se sobrepor ao brilho da população de bilhões de estrelas da galáxia, que os cientistas então identificam como quasares.
Os cientistas procuraram nas observações de arquivo do Hubble feitas na radiação ultravioleta emitida do centro da Mrk 231 para descobrir o que eles descrevem como propriedades extremas e surpreendentes.
Evidence for a_complex_enrichment_history_of_the_stream_from_fairall_9_sightlineSérgio Sacani
This study analyzes absorption spectra of the Magellanic Stream (MS) toward the quasar Fairall 9, obtained using the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) and the Very Large Telescope Ultraviolet and Visible Echelle Spectrograph (VLT/UVES). The spectra reveal absorption from multiple velocity components of the MS, indicating multiphase gas. Surprisingly, the sulfur abundance is found to be high ([S/H] = -0.30), five times higher than other MS sightlines, while the nitrogen abundance is lower ([N/H] = -1.15). This points to a complex enrichment history, where the gas toward Fair
Graphical 3D Modeling of Molecules and Nanostructures in Sub-nanometer Scale ...Stoyan Sarg Sargoytchev
The Basic Structures of Matter – Supergravitation Unified Theory (BSM-SG) reveals non-spherical shapes of the stable elementary particles, composed of two types of helical structures with opposite twisting. Proton and neutron have one and the same toroidal sub-structure, but the shape of proton is a twisted torus like the figure 8, while the neutron is a double folded. The shape of proton permits modulation of the space fabrics creating a positive E-field. At neutron such modulation is locked in the near field, so it is not detectable, but when in motion it creates a magnetic field. Due to it’s near E-field the neutron is stable over the proton, forming a deuteron. The electron is a different three body system with two intrinsic frequencies. Its structure and dynamic properties provide classical explanations of: Compton frequency, anomalous magnetic moment, spin and relativistic effect of mass increase. The near Coulomb field of the proton defines the trace of orbiting electron. The atomic nuclei are 3D compositions of protons and neutrons, kept by the attractive supergravitational forces, while balancing the repulsive forces between protons. The increase of number of protons reveals the build-up trend of the atomic nuclei showing a perfect match with the pattern of the Periodic Table. The features defining the valences and the angular restrictions of the chemical bonds are apparent. The rotational freedom of neutrons over protons is behind the nuclear magnetic moment. The BSM-SG atomic models are convenient for 3D graphical modeling of complex molecules and nanostructures with sub-nanometer resolution.
The magnetic method detects near-surface ferrous materials by measuring anomalies in the Earth's magnetic field. When ferrous objects are placed in the magnetic field, they develop an induced magnetic field that is superimposed on the Earth's field, creating a detectable anomaly. The method works best for detecting buried ferrous metals and can be used to map geology and locate buried infrastructure through magnetic susceptibility variations in rocks.
This document summarizes the results of a 180 ks Chandra-LETGS observation of Mrk 509 as part of a larger multi-wavelength campaign. The observation detected several absorption features in the X-ray spectrum originating from an ionized absorber, including ions with three distinct ionization degrees. The lowest ionized component is slightly redshifted and not in pressure equilibrium with the others, likely belonging to the host galaxy's interstellar medium. The other two components are outflowing at velocities of around -200 and -455 km/s. Simultaneous HST-COS observations detected 13 UV kinematic components, and at least three can be associated with the X-ray components, providing evidence that the UV and X-
This document summarizes the differentiation of the Earth. It discusses how the Earth initially formed as a molten mass and over time separated into layers with the heavier materials sinking to the center to form the core. The two main theories for this differentiation are homogeneous and heterogeneous accretion. Evidence from the Moon supports the Earth differentiating into layers early in its formation history around 4.5 billion years ago. The Earth is now composed of concentric layers that decrease in density from the iron-nickel core, to the silicate mantle, and finally the crust at the surface.
1) Geophysical surveys have been using measurements of the Earth's magnetic field for nearly 500 years since Gilbert showed that the Earth behaves like a large magnet.
2) Gravity and magnetic surveying methods are similar in that they both measure naturally occurring fields (potential fields), can use identical physical representations like magnetic monopoles, and have similar data acquisition and interpretation.
3) However, magnetic surveying also has differences from gravity - magnetic susceptibility of rocks can vary more than density, magnetism can be attractive or repulsive unlike gravity, magnetic sources always occur in pairs unlike gravity, and the magnetic field is time-dependent unlike gravity.
This document summarizes observations of the W49 giant molecular cloud (GMC) using the PMO 14m telescope and the Submillimeter Array (SMA). The PMO observations mapped the entire GMC in various molecular lines at scales up to 113 pc, while the SMA mosaic mapped the central star-forming region W49N at scales down to 0.5 pc. The observations are used to derive the mass structure of the GMC across all scales. The main findings are that the W49 GMC has a total gas mass of 1.1 million solar masses within 60 pc and 2x10^5 solar masses within 6 pc. The mass is distributed in a hierarchical network of filaments converging toward the central
Revealing the invisible universe from MaunakeaILOAHawaii
This document discusses submillimeter astronomy and the importance of Maunakea, Hawaii as a location for observing submillimeter wavelengths. It summarizes that submillimeter radiation reveals the earliest moments of star and galaxy formation, but this wavelength is blocked by Earth's atmosphere and can only be observed from a few locations worldwide, including Maunakea. The James Clerk Maxwell Telescope and its SCUBA camera made early discoveries in this field, and ongoing surveys continue to reveal new phenomena like the brightest stellar flare ever recorded in submillimeter wavelengths. The document also discusses the Event Horizon Telescope and its goal of directly imaging a black hole by observing in millimeter and submillimeter wavelengths where a black hole's event
The document repeats the phrase "1971Moon....3....3H" over 100 times. It appears to be referring to the year 1971 and the moon, but provides no other context or information.
The document summarizes observations of the unusual gamma-ray burst GRB 101225A. Key points:
- GRB 101225A had exceptionally long-lived gamma-ray emission and a subsequent bright X-ray transient with a hot thermal component.
- The optical emission over the first 10 days evolved as an expanding, cooling blackbody. An additional supernova component then emerged.
- The redshift is estimated to be 0.33 based on fitting the spectral energy distribution and light curve with a GRB-supernova template.
- The proposed progenitor is a merger of a helium star and neutron star that underwent a common envelope phase, expelling its hydrogen envelope. The explosion created a
Rings in the_haloes_of_planetary_nebulaeSérgio Sacani
This document presents the discovery of ring structures in the haloes of eight planetary nebulae, tripling the number known to have such rings. The rings are analyzed using image processing techniques to enhance their visibility. They find ring spacings range from less than 0.01 pc to 0.06 pc. This suggests ring spacing increases with time after the asymptotic giant branch phase. The properties of the rings support predictions of dust-driven wind instability models of mass loss but do not rule out other models. Analyzing the new detections provides insights into mass modulation processes late in stellar evolution.
This document describes the discovery of an unusual rectangular-shaped galaxy called LEDA 074886. Some key details:
- LEDA 074886 has an absolute magnitude of -17.3 and resembles an "emerald cut diamond" in shape with very boxy isophotes.
- It contains an embedded edge-on stellar disk of extent 1.2 kpc, with a rotation to dispersion ratio of 1.4.
- The authors speculate that LEDA 074886 may be the remnant of two merged disk galaxies, where the initial gas drove inward to form the inner disk, while the stars at larger radii experienced a dissipationless merger resulting in the rectangular shape.
-
This document discusses observations of extended X-ray and H-alpha emission about 11 arcminutes (11.6 kpc) north of the starburst galaxy M82. The total H-alpha flux from this region is 1.5×10−13 erg s−1 cm−2, comprising about 0.3% of M82's total H-alpha flux. Diffuse soft X-ray emission is also seen in the same region. The X-ray spectrum is well fit by a thermal plasma model with a temperature of 0.80±0.17 keV. The total unabsorbed X-ray flux is 1.4×10−13 erg s−1 cm−2, comprising about 0
This document reviews the observed properties of interstellar dust grains. It discusses dust extinction across ultraviolet to infrared wavelengths, including characteristic absorption features. Spectroscopic analysis reveals dust composition, such as polycyclic aromatic hydrocarbons and silicate materials. The review also examines dust emission from infrared to microwave, scattering properties, grain alignment with magnetic fields, and dust evolution over time.
High resolution image_of_a_cometary_globule_in_helix_nebulaSérgio Sacani
This document summarizes high-resolution observations of a cometary globule in the Helix Nebula made using the IRAM interferometer and SOFI infrared camera. The observations image the globule in the CO J=1-0 line and H2 v=1-0 S(1) line. They reveal that the head of the globule appears as a narrow peak in CO emission outlined by limb-brightened H2 emission facing the central star. Emission from both molecules extends into the tail region, providing new constraints on globule structure and evolution.
NGC 680 and NGC 5557 are early-type galaxies that were observed with deep optical imaging to study their outer morphologies. NGC 680 exhibits extended plumes and tails that appear connected to HI gas, as well as arcs and shells. NGC 5557 has a gigantic 160 kpc long narrow tail containing three star-forming objects. The features suggest that each galaxy underwent a major wet merger over 1-2 Gyr ago, with NGC 5557's merger dominating its formation history and making it a slow rotator, while NGC 680 rotates faster.
1) A statistical analysis of microlensing data from 2002-2007 reveals that planets are common, with specific abundances estimated as follows: 17% ± 6% of stars have Jupiter-mass planets between 0.3-10 Jupiter masses located 0.5-10 AU from the star. 52% ± 22% of stars have cool Neptunes of 10-30 Earth masses in the same region, and 62% ± 35% of stars have super-Earths of 5-10 Earth masses there.
2) Integrating the planet detection sensitivity over the detectable parameter space allows the derivation of the planet mass function, which is consistent with a power law. The best-fit suggests the average number of planets per star
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.
1) Geoelectric energy is a new source of electrical energy produced naturally from radioactive decay in the Earth's crust or artificially from nuclear waste decay.
2) This energy can be harnessed using solar cells to convert radiation into electricity or by installing converters in deep repositories where nuclear waste is stored.
3) Storing nuclear waste in areas with organic waste and complex hydrocarbons can safely protect repositories by converting radiation into fuels and gases while preventing earthquakes.
This document discusses the recycling of magnetic flux in the quiet Sun's corona. It presents a study that uses magnetogram observations to track photospheric magnetic flux fragments over time and models their evolution using a potential field approximation. The main findings are:
1) The quiet Sun's coronal flux is generally recycled on much shorter timescales, around 3 hours, than the corresponding recycling timescale of photospheric flux, which is around 8-19 hours.
2) When also considering emergence and cancellation of photospheric flux, the net replacement time of coronal flux is estimated to be only 1.4 hours.
3) The amount of magnetic reconnection driven by the motions and interactions of photospheric
The xmm newton-view_of_the_central_degrees_of_the_milk_waySérgio Sacani
Novas imagens do Observatório de Raios-X XMM-Newton da ESA revelaram alguns dos processos mais intensos que acontecem no coração da nossa Via Láctea.
As fontes brilhantes e pontuais que se destacam por toda imagem indicam os sistemas estelares binários onde uma das estrelas atingiu o final de sua vida, desenvolvendo para um objeto compacto e denso – uma estrela de nêutrons ou um buraco negro.
A região central da Via Láctea também contém jovens estrelas e aglomerados estelares e algumas dessas fontes são visíveis como pontos brancos e vermelhos brilhando na imagem, que se espalha por 1000 anos-luz.
A maior parte da ação ocorre no centro, onde nuvens difusas de gás estão sendo cavadas por ventos poderosos soprados por estrelas jovens, bem como por supernovas.
The document summarizes the first observations of the magnetic Kelvin-Helmholtz instability in the solar corona using high-resolution imaging from NASA's Solar Dynamics Observatory. The instability was detected on the northern flank of a fast coronal mass ejection, appearing as substructures or waves against the darker coronal background. Analysis found the observed phase speed of the waves to be about half the speed of the ejecta front, validating theories of the non-linear dynamics of this instability in magnetized plasma environments. The findings provide new insights into fundamental plasma processes in the solar atmosphere and solar-terrestrial system.
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.
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Todo mundo sabe que os raios produzidos pela Estrela da Morte em Guerra nas Estrelas não pode existir na vida real, porém no universo existem fenômenos que as vezes conseguem superar até a mais surpreendente ficção.
A galáxia Pictor A, é um desses objetos que possuem fenômenos tão espetaculares quanto aqueles exibidos no cinema. Essa galáxia localiza-se a cerca de 500 milhões de anos-luz da Terra e possui um buraco negro supermassivo no seu centro. Uma grande quantidade de energia gravitacional é lançada, à medida que o material cai em direção ao horizonte de eventos, o ponto sem volta ao redor do buraco negro. Essa energia produz um enorme jato de partículas que viajam a uma velocidade próxima da velocidade da luz no espaço intergaláctico, chamado de jato relativístico.
Para obter imagens desse jato, os cientistas usaram o Observatório de Raios-X Chandra, da NASA várias vezes durante 15 anos. Os dados do Chandra, apresentados em azul nas imagens, foram combinados com os dados obtidos em ondas de rádio a partir do Australia Telescope Compact Array, e são aparesentados em vermelho nas imagens.
A rare case of FR I interaction with a hot X-ray bridge in the A2384 galaxy c...Sérgio Sacani
Clusters of varying mass ratios can merge and the process significantly disturbs
the cluster environments and alters their global properties. Active radio galaxies are
another phenomenon that can also affect cluster environments. Radio jets can interact
with the intra-cluster medium (ICM) and locally affect its properties. Abell 2384
(hereafter A2384) is a unique system that has a dense, hot X-ray filament or bridge
connecting the two unequal mass clusters A2384(N) and A2384(S). The analysis of its
morphology suggests that A2384 is a post-merger system where A2384(S) has already
interacted with the A2384(N), and as a result hot gas has been stripped over a ∼ 1
Mpc region between the two bodies. We have obtained its 325 MHz GMRT data,
and we detected a peculiar FR I type radio galaxy which is a part of the A2384(S).
One of its radio lobes interacts with the hot X-ray bridge and pushes the hot gas in
the opposite direction. This results in displacement in the bridge close to A2384(S).
Based on Chandra and XMM-Newton X-ray observations, we notice a temperature and
entropy enhancement at the radio lobe-X-ray plasma interaction site, which further
suggests that the radio lobe is changing thermal plasma properties. We have also
studied the radio properties of the FR I radio galaxy, and found that the size and
radio luminosity of the interacting north lobe of the FR I galaxy are lower than those
of the accompanying south lobe.
Alma observations of_feeding_and_feedback_in_nearby_seyfert_galaxies_outflow_...Sérgio Sacani
ALMA observations of the Seyfert 2 galaxy NGC 1433 reveal a nuclear gaseous spiral structure within a nuclear ring encircling a nuclear stellar bar. Near the nucleus, there is intense high-velocity CO emission interpreted as an AGN-driven molecular outflow. The outflow involves a molecular mass of 3.6 million solar masses and a flow rate of about 7 solar masses per year. Continuum emission at the center is likely thermal dust emission from a molecular torus expected in this Seyfert 2 galaxy. The observations probe gas dynamics within 24 parsecs of the active galactic nucleus.
MUSE sneaks a peek at extreme ram-pressure stripping events. I. A kinematic s...Sérgio Sacani
- MUSE observations of the galaxy ESO137-001 reveal an extended gaseous tail over 30 kpc long traced by H-alpha emission, providing evidence of an extreme ram pressure stripping event as the galaxy falls into the massive Norma galaxy cluster.
- Analysis of the H-alpha kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center, with gravitational interactions not appearing to be the main mechanism of gas removal.
- The stripped gas retains evidence of the disk's rotational velocity out to around 20 kpc downstream, indicating the galaxy is moving radially along the plane of the sky, while
This document describes observations of the galaxy ESO137-001 using the MUSE instrument on the VLT. The key points are:
1) MUSE observations reveal an extended gas tail stretching over 30 kpc from the galaxy, tracing ongoing ram pressure stripping as it falls into the Norma galaxy cluster.
2) Analysis of the gas kinematics and stellar velocity field show that ram pressure has removed the interstellar medium from the outer disk while the primary tail is still fed by gas from the galaxy center.
3) The stripped gas retains evidence of the disk's rotational velocity out to 20 kpc downstream, indicating the galaxy is moving radially through the cluster. Beyond this the gas shows greater turbulence,
This pilot survey used modest aperture telescopes to image 8 nearby spiral galaxies in order to search for stellar tidal streams. Ultra-deep imaging revealed 6 previously undetected extensive (up to 30 kpc) stellar structures likely from tidally disrupted satellites. A diversity of tidal feature morphologies was found, including great circle-like streams, remote shells, and jets emerging from disks. Simulations predict tidal debris should be common and match the observed variety, providing evidence minor mergers have shaped disk galaxies since z=1.
This document summarizes molecular dynamics simulations of radiation damage in zirconia (ZrO2) at energies ranging from 0.1-0.5 MeV. The simulations find that while zirconia is highly resistant to amorphization, there is still a large number of point defects and small defect clusters created by the radiation. However, these defects are isolated from each other, resulting in dilute damage that does not disrupt the long-range crystalline structure. The simulations quantify the number of displacements and defects over time and find that electronic energy losses play an important role in the damage evolution. The findings have implications for using zirconia in nuclear waste storage by suggesting radiation can create many point defects even while
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
This document summarizes research on using the enhanced electric field generated by surface plasmons on gold nanoparticles to non-resonantly excite photochromic molecules. The researchers coated gold nanospheres with a photochromic molecule called DAE1 and showed that 800nm light, which does not normally convert DAE1, was able to do so in the presence of the nanoparticles. They varied experimental conditions like nanoparticle size and structure. Images were also taken of plasmonic antennas made of nanorods that generate even stronger electric fields and could potentially induce conversion at even longer wavelengths than 800nm.
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
Alma observations of_feed_and_feedback_in_nearby_seyfert_galaxiesSérgio Sacani
The ALMA observations of NGC 1433 reveal a nuclear gaseous spiral structure within the central kpc. This spiral winds up into a pseudo-ring at ~200 pc from the center. Near the nucleus, there is intense high-velocity CO emission up to 200 km/s that is interpreted as an outflow, involving 3.6 million solar masses of molecular gas and a flow rate of ~7 solar masses per year. The outflow could be driven by both the central star formation and AGN through its radio jets. Continuum emission at 0.87 mm is detected only at the very center and likely comes from thermal dust emission from the molecular torus expected in this Seyfert 2 galaxy.
Solving the Multimessenger Puzzle of the AGN-starburst Composite Galaxy NGC 1068Sérgio Sacani
Multiwavelength observations indicate that some starburst galaxies show a dominant nonthermal contribution from
their central region. These active galactic nuclei (AGN)-starburst composites are of special interest, as both
phenomena on their own are potential sources of highly energetic cosmic rays and associated γ-ray and neutrino
emission. In this work, a homogeneous, steady-state two-zone multimessenger model of the nonthermal emission
from the AGN corona as well as the circumnuclear starburst region is developed and subsequently applied to the
case of NGC 1068, which has recently shown some first indications of high-energy neutrino emission. Here, we
show that the entire spectrum of multimessenger data—from radio to γ-rays including the neutrino constraint—can
be described very well if both, starburst and AGN corona, are taken into account. Using only a single emission
region is not sufficient.
One tenth solar_abundances_along_the_body_of-the_streamSérgio Sacani
This document summarizes a study that analyzed spectra from four background quasars to measure the chemical abundances along the Magellanic Stream. Two key findings are:
1) The sightlines toward RBS 144 and NGC 7714 yielded metallicities of around 0.1 times the solar value, indicating a uniform low abundance along the main body of the Stream. This supports models where the Stream was stripped from the SMC around 1-2.5 billion years ago when the SMC had a metallicity of around 0.1 solar.
2) A higher metallicity of around 0.5 solar was found in the inner Stream toward Fairall 9, sampling a filament traced to the LMC. This shows the bifurc
Similar to Solar nebula magnetic_fields_recorded_in_the_semarkona_meteorite (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
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
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
Unlocking the mysteries of reproduction: Exploring fecundity and gonadosomati...AbdullaAlAsif1
The pygmy halfbeak Dermogenys colletei, is known for its viviparous nature, this presents an intriguing case of relatively low fecundity, raising questions about potential compensatory reproductive strategies employed by this species. Our study delves into the examination of fecundity and the Gonadosomatic Index (GSI) in the Pygmy Halfbeak, D. colletei (Meisner, 2001), an intriguing viviparous fish indigenous to Sarawak, Borneo. We hypothesize that the Pygmy halfbeak, D. colletei, may exhibit unique reproductive adaptations to offset its low fecundity, thus enhancing its survival and fitness. To address this, we conducted a comprehensive study utilizing 28 mature female specimens of D. colletei, carefully measuring fecundity and GSI to shed light on the reproductive adaptations of this species. Our findings reveal that D. colletei indeed exhibits low fecundity, with a mean of 16.76 ± 2.01, and a mean GSI of 12.83 ± 1.27, providing crucial insights into the reproductive mechanisms at play in this species. These results underscore the existence of unique reproductive strategies in D. colletei, enabling its adaptation and persistence in Borneo's diverse aquatic ecosystems, and call for further ecological research to elucidate these mechanisms. This study lends to a better understanding of viviparous fish in Borneo and contributes to the broader field of aquatic ecology, enhancing our knowledge of species adaptations to unique ecological challenges.
Solar nebula magnetic_fields_recorded_in_the_semarkona_meteorite
1. Solar nebula magnetic fields recorded in the Semarkona meteorite
Roger R. Fu et al.
Science 346, 1089 (2014);
DOI: 10.1126/science.1258022
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2. REPORTS
◥
PALEOMAGNETISM
Solar nebula magnetic fields recorded
in the Semarkona meteorite
Roger R. Fu,1* Benjamin P. Weiss,1 Eduardo A. Lima,1 Richard J. Harrison,2
Xue-Ning Bai,3 Steven J. Desch,4 Denton S. Ebel,5 Clément Suavet,1
Huapei Wang,1 David Glenn,6 David Le Sage,7 Takeshi Kasama,8
Ronald L. Walsworth,6,7 Aaron T. Kuan9
Magnetic fields are proposed to have played a critical role in some of the most enigmatic
processes of planetary formation by mediating the rapid accretion of disk material
onto the central star and the formation of the first solids. However, there have been no
experimental constraints on the intensity of these fields. Here we show that dusty
olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular
field of 54 21 microteslas. This intensity supports chondrule formation by nebular
shocks or planetesimal collisions rather than by electric currents, the x-wind, or other
mechanisms near the Sun. This implies that background magnetic fields in the terrestrial
planet-forming region were likely 5 to 54 microteslas, which is sufficient to account for
measured rates of mass and angular momentum transport in protoplanetary disks.
Astronomical observations of young stellar
objects indicate that early planetary sys-tems
evolve through a protoplanetary disk
phase in <5 million years (My) following the
collapse of their parent molecular clouds
(1, 2). Disk evolution on such short time scales
requires highly efficient inward transport of mass
accompanied by outward angular momentum
transfer, which allows disk material to accrete
onto the central star while delivering angular
momentum out of the protoplanetary system.
The mechanism of this rapid mass and angu-lar
momentum redistribution remains unknown.
Several proposed processes invoke a central role
for nebular magnetic fields. Among these, the
magnetorotational instability (MRI) and mag-netic
braking predict magnetic fields with inten-sities
of ~100 mT at 1 astronomical unit (AU) in
the active layers of the disk (3, 4). Alternatively,
transport by magnetocentrifugal wind (MCW)
requires large-scale, ordered magnetic fields
stronger than ~10 mT at 1 AU. Finally, nonmag-netic
effects such as the baroclinic and Goldreich-
Schubert-Fricke instabilitiesmay be the dominant
mechanism of angular momentum transport in
the absence of sufficiently strong magnetic fields
(5). Direct measurement of magnetic fields in
the planet-forming regions of the disk can po-tentially
distinguish among and constrain these
hypothesized mechanisms.
Although current astronomical observations
cannot directly measure magnetic field strengths
in planet-forming regions [(6, 7); supplemen-tary
text], paleomagnetic experiments on me-teoritic
materials can potentially constrain the
strength of nebular magnetic fields. Chondrules
RESEARCH
are millimeter-sized lithic constituents of prim-itive
meteorites that formed in transient heat-ing
events in the solar nebula. If a stable field
was present during cooling, they should have ac-quired
a thermoremanent magnetization (TRM),
which can be characterized via paleomagnetic
experiments. Besides assessing the role of mag-netic
fields in disk evolution, such paleomagnetic
measurements would constrain the currently un-known
mechanism of chondrule formation.
Chondrules likely constituted a sizable fraction
of the mass of asteroids and terrestrial planet
precursors and may have facilitated the accre-tion
of the first planetesimals (8, 9). The forma-tion
of chondrules therefore very likely represents
a key stage in the evolution of the early solar
system. The ambient magnetic field strength is
a distinguishing characteristic among chondrule
formation models. The x-wind model implies
strong stellar fields of >80 to 400 mT (10). In
contrast, magnetic fields in the nebular shock
and planetesimal collision models are likely con-siderably
lower than 100 mT (11, 12).
Previous paleomagnetic measurements of in-dividual
chondrules have focused mostly on the
Allende CV chondrite (13). However, owing to ex-tensive
aqueous alteration on the CV parent body,
magnetic phases in Allende chondrules are sec-ondary
and do not retain pre-accretional magnet-ization
[i.e., magnetization acquired during the last
heating of chondrules in the nebula and before the
accretion of the meteorite's parent body; (14)].
Reliable recovery of preaccretional magnetization
requires samples that have avoided appreciable
postaccretional remagnetization processes.
Among the most pristine known meteorites is
the Semarkona LL3.00 ordinary chondrite. We
conducted paleomagnetic studies on Semarkona,
1Department of Earth, Atmospheric and Planetary Sciences,
Massachusetts Institute of Technology (MIT), Cambridge,
MA, USA. 2Department of Earth Sciences, University of
Cambridge, Cambridge, UK. 3Hubble Fellow, Harvard-
Smithsonian Center for Astrophysics, Cambridge, MA, USA.
4School of Earth and Space Exploration, Arizona State
University, Tempe, AZ, USA. 5Department of Earth and
Planetary Sciences, American Museum of Natural History
(AMNH), New York, NY, USA. 6Harvard-Smithsonian Center
for Astrophysics, Cambridge, MA, USA. 7Department of
Physics, Harvard University, Cambridge, MA, USA. 8Center
for Electron Nanoscopy, Technical University of Denmark,
Kongens Lyngby, Denmark. 9School of Engineering and
Applied Science, Harvard University, Cambridge, MA, USA.
*Corresponding author. E-mail: rogerfu@mit.edu
Dusty olivines 200 μm
Dusty Fe grains
Silica
500 nm
Fig. 1. Dusty olivine-bearing chondrules from the Semarkona meteorite. (A) Optical photo-micrograph
of chondrule DOC4 showing the location of dusty olivine grains. Image taken in reflected
light with crossed polarizers. (B) Annular dark-field scanning transmission electron microscope
(STEM) image of four dusty olivine Fe grains from chondrule DOC5. Brightness in image reflects
column-averaged atomic number; darker grains are smaller in size, implying a higher relative abundance
of olivine at their location and hence a lower mean atomic number. The euhedral morphology and
chemical homogeneity of the Fe grains is apparent, which indicate the lack of secondary recrystallization
and alteration. Such Fe grains are the primary carriers of preaccretional magnetization in Semarkona
chondrules.
SCIENCE sciencemag.org 28 NOVEMBER 2014 • VOL 346 ISSUE 6213 1089
3. RESEARCH | REPORTS
focusing in particular on dusty olivine-bearing
chondrules (Fig. 1). Dusty olivine crystals consist
of submicrometer–sized grains of nearly pure
body-centered cubic (bcc) Fe (kamacite) em-bedded
in forsteritic olivine (15). Such olivine
grains are found in approximately 1 in 10 chon-drules
in ordinary chondrites.
Because of their unique compositional and mag-netic
properties, dusty olivine grains are expected
to retain preaccretional magnetization. The small
grain size of dusty olivine metal implies that most
are in the single domain (SD) or single vortex (SV)
states, which can retain stable magnetization over
the history of the solar system (16–19). Further, the
Ni-poor composition (Ni <2 weight %) of dusty
olivine metal precludes metamorphic recrystal-lization
(15, 20). The domain states of dusty olivine
metals imply very high coercivities ranging up to
>200 mT, as confirmed by our demagnetization
experiments (see below). The magnetization of
grains with such high coercivities should not have
been much altered by the low shock pressures
likely experienced by Semarkona [4 to 10 GPa
(21, 22)]. Finally, the low porosities of the sur-rounding
olivine crystals have protected metal
from aqueous alteration (Fig. 1B).
The distinctive, high coercivities of dusty oli-vine
grains allow for the isolation of their rem-anent
magnetization during alternating field
(AF) demagnetization as larger (10 to 100 mm)
mesostasis metal grains are expected to demag-netize
at AF levels <50 mT (23). Furthermore,
because the postaccretional peak metamorphic
temperature of Semarkona was likely only 200°
to 260°C (24, 25), preaccretional remanence in
dusty olivine metals should be isolated upon
laboratory (1 hour duration) thermal demag-netization
to <450°C assuming that metamor-phism
lasted ~5 My (16, 19). In summary, no
known postaccretional process is likely to have
compromised preaccretional remanent magne-tization
in Semarkona dusty olivines; strong-field
AF demagnetization or thermal demagnetization
above ~450°C is expected to isolate the preaccre-tional
component of magnetization.
We isolated eight dusty olivine-bearing chon-drules
from two 15 mm by 10 mm by 150 mm–
thick sections of Semarkona provided by the
American Museum of Natural History (AMNH).
Both sections contain fusion crust along one
edge. We also extracted 5 non-dusty olivine-bearing
chondrules and 29 bulk (i.e., mixed
matrix and chondrule) samples to characterize
any postaccretional overprints. All extracted
samples are mutually oriented to within 5°. Owing
to their weak moments [natural remanent mag-netization
(NRM) ranging between 10−10 and 3 ×
10−12 A·m2 before demagnetization], chondrules
were measured with the superconducting quan-tum
interference device (SQUID) microscope
(26, 27) at the MIT Paleomagnetism Laboratory
(Fig. 2). Supporting magnetic imaging measure-ments
with higher spatial resolution were per-formed
with a nitrogen-vacancy (NV) quantum
diamond microscope (supplementary text).
Bulk samples were subjected to AF demag-netization
up to 85 to 145 mT or thermal de-magnetization
up to 580°C. We identified three
unidirectional postaccretional overprints in our
Semarkona samples: two low coercivity (LCa and
LCb) and one medium coercivity (MCa) compo-nents.
Twenty bulk samples carry the LCa overprint
blocked up to between 4.5 and 13 mT (Fig. 3). This
component is present in both fusion crust material
and meteorite interior samples, indicating that it
was acquired after arrival on Earth. Removal of
the LCa magnetization during thermal demag-netization
to only 70°C indicates that it is likely a
viscous remanent magnetization (VRM) acquired
during long-term exposure to the Earth’s field.
In contrast, the MCa overprint is only present
in samples within 4.7 mm of the fusion crust. The
mean paleointensity of this component based
on the isothermal remanent magnetization (IRM)
and anhysteretic remanent magnetization (ARM)
normalization methods (76 mT) is within uncer-tainty
of the Earth’s magnetic field. We conclude
2 4 6 8
2
240-360 mT
–2
–4
–6
–8
–10
5 10 15
5
575-625°C
– 5
– 10
– 15
– 20
– 25
– 30
Up
East
(x10-11 Am2)
East
(x10-13 Am2)
140-200 mT 65-70 mT
Up – East
North – East
Components:
LC
HC
NRM
5
250°C
NRM
450°C
22.5 mT
725-780°C
500°C
100°C
Up – East
North – East
Components:
350°C
40 mT
LCb
HT
E
N
70 mT
40 mT
20 mT
NRM
Bz (nT)
150
100
50
0
−50
−100
−150
20 mT
Fig. 2. AF and thermal demagnetization of single dusty olivine-bearing
chondrules measured with SQUID microscopy. Orthogonal projection dia-grams
showing the evolution of the natural remanent magnetization (NRM) of
two chondrules upon progressive demagnetization. Open and solid circles
indicate the projection of the NRM vector onto the vertical (up-east) and
horizontal (north-east) planes, respectively. (A) AF demagnetization of DOC1
reveals a low coercivity (LC) overprint removed by 20 mT and higher
coercivity (HC) magnetization that persists to >290 mT while decaying in
magnitude toward the origin. Insets show associated magnetic field maps
measured with the SQUID microscope at the indicated demagnetization
levels where positive (red) field values are in the up direction. The stable
directionality and steady decay of the magnetization can be seen during AF
application above 20 mT. (B) Mixed AF and thermal demagnetization of
DOC8 shows the removal of the postaccretional LCb overprint by 20.0 mT
(green points), a stationary moment between room temperature and ~400°C
(gray), and an origin-trending high temperature (HT) component removed by
780°C (red). Steps above 40 mT or 575°C have been averaged to suppress
noise.
1090 28 NOVEMBER 2014 • VOL 346 ISSUE 6213 sciencemag.org SCIENCE
4. that the MCa component was acquired during
heating from atmospheric passage. Finally, a small
subset of seven samples from one edge of our
Semarkona section carry the LCb overprint,
which is completely removed by AF demagne-tization
up to between 10.5 and 30 mT. The high
intensity of the LCb component (NRM to satu-ration
IRM ratio of 0.23) suggests that it was
acquired during exposure to artificial magnetic
fields. Only two dusty olivine-bearing chondrules
carried the LCb overprint, which was fully re-moved
upon AF application to 20 mT. To sum-marize,
all samples >1.0 mm from the fusion crust,
which include all dusty olivine-bearing chondrules,
do not carry any postaccretional remagnetiza-tion
other than the LCa, MCa, and LCb com-ponents.
These overprints, if present, are readily
identified and removed via AF cleaning.
Eight dusty olivine-bearing chondrules were
subjected to AF and thermal demagnetization
up to 290 to 420 mT or 780°C. Six of these were
found to carry a high coercivity (HC) or high
temperature (HT) component of magnetization.
We argue based on seven lines of evidence that
these HC/HT components are preaccretional
TRMs (supplementary text). (i) HC/HT compo-nents
decay to the origin upon demagnetiza-tion,
which is the expected behavior of primary
magnetization (Fig. 2). (ii) The HC/HT magne-tization
directions in the six chondrules are col-lectively
random, passing the conglomerate test
at the 95% confidence level [Fig. 3; (28)]. No
HC/HT component is oriented in the direction of
any of the postaccretional overprints. (iii) The
HC magnetizations in chondrules DOC3 and
DOC4, which were each partitioned into two
subsamples, are unidirectional within each chon-drule
and inconsistent with random magnetiza-tions
at the 99% confidence level. Such uniformity
is expected of a TRM acquired by individual
chondrules cooling in the solar nebula because
the field should be uniform across the submilli-meter
scale of each sample (14). (iv) The blocking
temperature range of the HT component (350°
to 750°C) agrees closely with that expected of a
preaccretional magnetization that was partially
demagnetized for ~5 My at ~200°C [Fig. 2B;
(16, 19)], which is the estimated metamorphic
temperature for Semarkona on the LL parent
body (16, 25). (v) Magnetic field maps of dusty
olivine-bearing chondrules confirm that the HC
magnetization is carried by dusty olivines, which
formed in the nebula and are expected to retain
preaccretional magnetization as outlined above.
(vi) The magnetization direction acquired dur-ing
cooling for a spinning chondrule is expected
to be parallel to its rotation axis (29). The close
alignment between the HC directions and the
short axes of our chondrules, which are likely
related to the rotation axis (supplementary text),
are nonrandom at the 98% confidence level,
suggesting that HC/HT magnetizations were in-deed
acquired parallel to the spin axis. (vii) The
coercivity spectrum of the HC component of
dusty olivine-bearing chondrules is very similar
to that of an ARM and dissimilar to that of an
IRM, which suggests that the HC component was
acquired as a TRM (30). We therefore conclude
with high confidence that the HC/HT magne-tizations
observed in dusty olivine-bearing chon-drules
are TRMs acquired in the solar nebula.
TRM acquisition experiments on analogs of
dusty olivine chondrules have shown that the
ARM normalization method potentially produces
RESEARCH | REPORTS
paleointensities accurate to ~40% [2s; (30)]. As-suming
that the five chondrules with recovered
paleointensities formed in similar magnetic field
conditions in the nebula, our nominal ARM pa-leointensities
for six dusty olivines yielded a
mean value of 27 mT. The morphology of chon-drules
(31) and the apparent correspondence
between HC magnetization directions and the
short axes of our chondrule samples (see above
paragraph) strongly suggest that chondrules were
rotating during remanence acquisition in the so-lar
nebula. In the case of rotation around a single
axis, which is the expected motion inherited from
cooling of a viscous droplet, the true mean field
intensity should have been greater than our ex-perimental
paleointensity by a factor of 2 (sup-plementary
text). Meanwhile, precession of the
chondrule’s rotation axis would imply a multipli-cative
factor of up to 4. However, given the high
inferred rotation rates of chondrules (>50 s−1),
the magnitudes of effects that may lead to pre-cession
are comparatively small. Therefore, we
adopt nonprecessing rotation as the most likely
state of cooling chondrules and recommend a
value of 54 T 21 mT (2s) for the ambient nebular
field strength. Although unlikely, if chondrules
did not rotate or precessed strongly during rem-anence
acquisition, the corresponding estimated
ambient field strength would be 27 T 8 mT or
108 T 42 mT (2s), respectively.
Our paleointensity constrains the magnetic
field environment during the last time the chon-drule
cooled through the 765° to 350°C blocking
temperature range of the HC/HT component,
which likely was the chondrule-forming event.
Our recommended paleointensity is significant-ly
lower than the >80 to 400 mT expected for
chondrules purportedly formed in the x-wind
model (10). Furthermore, mechanisms that in-voke
intense electric currents such as magnetic
reconnection flares and current sheets predict
strong fields >500 mT during chondrule heating
(32). The short-circuit instability may also imply
similarly strong fields at high temperature (33),
although the decay of field strength below 765°C
has not been studied in detail. In contrast, assum-ing
that magnetic fields inherited from the col-lapsing
molecular cloud were on the order of
10 mT (12), nebular shocks, which may enhance
the ambient magnetic field by a factor of <10,
would result in paleointensities of <100 mT (11).
Meanwhile, planetesimal collisions would likely
not perturb the background field. Therefore,
nebular shocks and planetesimal collisions are
the chondrule formation models most consist-ent
with our measured paleointensities.
Adopting nebular shocks and planetesimal
collisions as the most likely origins of chon-drules,
background magnetic fields in the neb-ula
may have been amplified by a factor between
1 and 10 during chondrule formation. We there-fore
infer that background magnetic fields in the
solar nebula were between 5 and 54 mT (11).
Assuming Semarkona chondrules formed near
2.5 AU, which is the present-day location of
S-type asteroids (34), the vertical distribution
of dust in the nebula strongly suggests that
Fig. 3. Magnetization direc-tions
in Semarkona chon-drules
and bulk samples.
Equal area stereonet
projection diagram where
colored points denote high
coercivity or high temperature
(HC/HT) magnetization in
individual dusty olivine-bearing
sample or subsamples. Circles
indicate the associated maxi-mum
angular deviation (MAD)
obtained from principle com-ponents
analysis. Each color
represents a single chondrule
with chondrules DOC3 and
DOC4 having two subsamples
each. Black stars and associ-ated
ovals represent the mean
directions of the three postac-cretional
overprints identified
N
E
W
DOC5
DOC3
3S
DOC4 30°
4N
4S
3N
DOC1
DOC2
MCa
LCa
60°
LCb
DOC8
Hemisphere
Upper
Lower
Components
DOC HC/HT
Mean bulk sample
overprints
from bulk samples and their
95% confidence intervals.
S
Open symbols represent the
upper hemisphere; solid symbols represent the lower hemisphere. The wide scatter of the HC/HT
magnetizations, the unidirectionality of subsamples from DOC3 and DOC4, and their noncorrespon-dence
to the directions of postaccretional overprints provide strong evidence for a preaccretional origin
of the HC/HT magnetizations in dusty olivine-bearing chondrules.
SCIENCE sciencemag.org 28 NOVEMBER 2014 • VOL 346 ISSUE 6213 1091
5. RESEARCH | REPORTS
chondrule formation took place in the weakly
ionized “dead zone,” which contains gas poorly
coupled to localmagnetic fields and occurs within
~3 gas scale heights of the midplane (35). Our
measurements therefore indicate that a substan-tial
magnetic field [ yet still well below the ~400 mT
equipartition field strength (3)] existed in the dead
zone, potentially as a result of fields inherited from
the collapse of the solar system’s parent molecular
cloud. Given our measured field strengths, mass ac-cretion
driven by the MRI or magnetic braking at
2.5 AU would have been <0.04 × 10−8 to 3.5 × 10−8
Msun year−1, where Msun is the Sun’s mass (sup-plementary
text). Meanwhile, the MCW model
would predict mass accretion rates of 0.3 × 10−7
to 30 × 10−7Msun year−1 or less. The inferred age of
Semarkona chondrules is 2 to 3 My after the first
calcium alunimum–rich inclusions (36). Given that
protoplanetary disks are observed to have ac-cretion
rates of 10−9-10−7 Msun year−1 at 2 to 3 My
after collapse of their parent molecular clouds (2),
both magnetic mechanism could fully account for
the expected accretion rates. This suggests that
magnetic fields govern the observed rapid trans-formation
of protoplanetary disks into planetary
systems around Sun-like stars.
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ACKNOWLEDGMENTS
We thank S. A. Balbus, A. J. Brearley, H. C. Connolly, A. M. Hughes,
B. C. Johnson, J. L. Kirschvink, M. Mac Low, G. J. MacPherson,
M. I. Petaev, D. D. Sasselov, H. E. Schlichting, J. B. Simon,
N. Turner, and B. Zanda for discussions that improved the
manuscript. We also thank J. Gross, S. Wallace, and Z. I. Balogh for
help with SEM and STEM sample analyses and acknowledge
S.-C. L. L. Lappe, N. S. Church, S. Russell, M. Uehara, and
N. Nakamura for pioneering work on the magnetism of dusty
olivines. We thank T. F. Peterson for supporting critical
instrumentation and analysis costs. R.R.F., B.P.W., E.A.L., S.J.D.,
and C.S. thank the NASA Origins Program, while R.R.F. and B.P.W.
thank the U.S. Rosetta Project, Jet Propulsion Laboratory for
support. R.R.F. thanks the NSF Graduate Research Fellowship
Program, and C.S. thanks the NASA Lunar Science Institute and
the NASA Solar System Exploration and Research Virtual Institute
for support. R.J.H. and T.K. thank the European Research Council
under the European Union’s Seventh Framework Programme and
the Leverhulme Trust for support. X.N.B. acknowledges support
from NASA through the Hubble Fellowship. D.G., D.L.S., and R.L.W.
thank the Defense Advanced Research Projects Agency QuASAR
program and the NSF for support.
SUPPLEMENTARY MATERIALS
www.sciencemag.org/content/346/6213/1089/suppl/DC1
Supplementary Text
Figs. S1 to S12
Tables S1 to S4
References (37–125)
Database S1
30 June 2014; accepted 31 October 2014
Published online 13 November 2014;
10.1126/science.1258022
MATERIALS SCIENCE
Dynamic mechanical behavior of
multilayer graphene via supersonic
projectile penetration
Jae-Hwang Lee,1,2* Phillip E. Loya,1 Jun Lou,1 Edwin L. Thomas1*
Multilayer graphene is an exceptional anisotropic material due to its layered structure
composed of two-dimensional carbon lattices. Although the intrinsic mechanical
properties of graphene have been investigated at quasi-static conditions, its
behavior under extreme dynamic conditions has not yet been studied.We report the
high–strain-rate behavior of multilayer graphene over a range of thicknesses from
10 to 100 nanometers by using miniaturized ballistic tests. Tensile stretching of the
membrane into a cone shape is followed by initiation of radial cracks that approximately
follow crystallographic directions and extend outward well beyond the impact area.
The specific penetration energy for multilayer graphene is ~10 times more than literature
values for macroscopic steel sheets at 600 meters per second.
Graphene, the atomic monolayer building
block of graphite, is known for its excep-tionally
high intrinsic strength and stiff-ness
arising from the two-dimensional (2D)
hexagonal lattice of covalently bonded
carbon atoms. Recently, graphene’s in-plane
Young’s modulus (Y‖) was measured to be more
than 1.0 TPa using atomic force microscope
nanoindentation (1). Because tensile mechani-cal
stresses in a material cannot be transmitted
faster than the speed of sound [c ~ (Y/r)1/2, where
r is the density of the material], the nonequil-ibrium
local stress arising from the inertial effect
becomes important under dynamic conditions
accompanying high–strain-rate, predominantly
tensile loading (2). In this regard, the relatively
low density (~2200 kg m−3) of graphene (3),
along with its high modulus, leads to a superior
in-plane speed of sound (c‖ ~ 22.2 km s−1), im-plying
that concentrated stresses applied under
extreme conditions can rapidly be delocalized.
Nanoindentation has served as an effective
technique to study the tensile mechanical prop-erties
of monolayer graphene. It is inherently
a low-speed test (<<1 m s−1), but strain rates
can reach ~105 to 106 s−1 for very thin samples
(4), whereas most high-speed, high–strain-rate
mechanical characterization techniques, such as
split-Hopkinson pressure bar (5) and ballistic
tests (6), are inappropriate for testing very thin
specimens. To address high-speed and high–
strain-rate tensile-dominated penetration of thin
films, we improved our laser-induced projectile
impact test (LIPIT) (7). In this advanced LIPIT
(or “a-LIPIT”), a single micrometer-size solid
silica sphere (or “m-bullet”) is fired at a high speed
1Department of Materials Science and NanoEngineering, Rice
University, Houston, TX 77005, USA. 2Department of Mechanical
and Industrial Engineering, University of Massachusetts,
Amherst, MA 01003, USA.
*Corresponding author. E-mail: leejh@umass.edu (J.-H.L.); elt@
rice.edu (E.L.T.)
1092 28 NOVEMBER 2014 • VOL 346 ISSUE 6213 sciencemag.org SCIENCE