- Mineralogical Society of America
... in the early Solar System, such as heating and collision, and were eventually incorporated into the parent bodies of primitive meteorites. Presolar grains are identified by their having isotopic compositions that can be drastically different from terrestrial, and from one another, depending on their ...
... in the early Solar System, such as heating and collision, and were eventually incorporated into the parent bodies of primitive meteorites. Presolar grains are identified by their having isotopic compositions that can be drastically different from terrestrial, and from one another, depending on their ...
The Evolution of Long-Period Comets
... The observed distribution of long-period (> 200 yr) comet orbits has proved dicult to reconcile with theory. Among the discrepancies is the \fading problem": the fraction of comets in the observed sample which are presumed to have made more than one perihelion passage since leaving the Oort cloud i ...
... The observed distribution of long-period (> 200 yr) comet orbits has proved dicult to reconcile with theory. Among the discrepancies is the \fading problem": the fraction of comets in the observed sample which are presumed to have made more than one perihelion passage since leaving the Oort cloud i ...
A Review of the 0.1 Reconnection Rate Problem
... found that all models with the Hall term (two-fluid, hybrid, and full particle-in-cell) had rates comparable to the 0.1 value (Birn et al. 2001). Many concluded from this that the Hall term was the cause of reconnection having a rate of 0.1. While no there is no first-principles theory showing the r ...
... found that all models with the Hall term (two-fluid, hybrid, and full particle-in-cell) had rates comparable to the 0.1 value (Birn et al. 2001). Many concluded from this that the Hall term was the cause of reconnection having a rate of 0.1. While no there is no first-principles theory showing the r ...
Systematic Study of Mass Loss in the Evolution of Massive Stars
... are short lived. Nevertheless, their characteristics (e.g. high luminosity, large mass loss rate, complex nuclear burning, final fate, etc.) make them extremely important for many sub-fields of astrophysics. For example, because of their high luminosity, they are the only stars that can be observed ...
... are short lived. Nevertheless, their characteristics (e.g. high luminosity, large mass loss rate, complex nuclear burning, final fate, etc.) make them extremely important for many sub-fields of astrophysics. For example, because of their high luminosity, they are the only stars that can be observed ...
Observations of the Magnetic Fields Inside and Outside the
... direction of electric current I). Since the electric currents are mostly alternating, the senses of the assoicated magnetic fields will also reverse with time. The above-ground lines can be seriously affected by the passage of solar magnetic storms speeding away from the Sun and encountering the Ear ...
... direction of electric current I). Since the electric currents are mostly alternating, the senses of the assoicated magnetic fields will also reverse with time. The above-ground lines can be seriously affected by the passage of solar magnetic storms speeding away from the Sun and encountering the Ear ...
Radiation-driven wind models of massive stars
... ionizes the surrounding nebula and heats the associated H II region. As massive stars are mostly seen grouped in young clusters, wind-blown bubbles around these stars interact with each other and subsequently evolve into superbubbles. These superbubbles are thought to be places for the propagation o ...
... ionizes the surrounding nebula and heats the associated H II region. As massive stars are mostly seen grouped in young clusters, wind-blown bubbles around these stars interact with each other and subsequently evolve into superbubbles. These superbubbles are thought to be places for the propagation o ...
Studies of dark matter in and around stars
... form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models, dark matter particles can annihilate with each other in ...
... form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models, dark matter particles can annihilate with each other in ...
PSRD: Chondrules: Important, but Possibly Unfathomable
... actively spewing out material that in principle could interact with the dust in the solar nebula, or at least transfer heated products to further out in the solar nebula. These ideas are good, but none has detailed how the mechanism reproduces chondrule thermal histories that include rapid heating a ...
... actively spewing out material that in principle could interact with the dust in the solar nebula, or at least transfer heated products to further out in the solar nebula. These ideas are good, but none has detailed how the mechanism reproduces chondrule thermal histories that include rapid heating a ...
Circumstellar molecular composition of the oxygen
... Circumstellar molecules have been extensively observed both in the form of surveys of a single molecular species and in the form of searches for various molecular species in a limited number of carefully selected sources. The aim of these studies was to derive (i) the mass-loss rate (from CO rotatio ...
... Circumstellar molecules have been extensively observed both in the form of surveys of a single molecular species and in the form of searches for various molecular species in a limited number of carefully selected sources. The aim of these studies was to derive (i) the mass-loss rate (from CO rotatio ...
Stars as cosmological tools: giving light to Dark Matter
... Figure 1.1: The Coma cluster observed by the X-ray telescope ROSAT [6]. The temperature of the intracluster gas is used to infer the total mass of the cluster, revealing the existence of large amounts of invisible mass. virial theorem (relating the kinetic and potential energy of the system), he est ...
... Figure 1.1: The Coma cluster observed by the X-ray telescope ROSAT [6]. The temperature of the intracluster gas is used to infer the total mass of the cluster, revealing the existence of large amounts of invisible mass. virial theorem (relating the kinetic and potential energy of the system), he est ...
YEAR - University of Maryland Astronomy
... Dr. Doug Hamilton Dr. Casey Lisse Dr. Eve Ostriker Dr. John C. L. Wang Dr. Jim Stone ...
... Dr. Doug Hamilton Dr. Casey Lisse Dr. Eve Ostriker Dr. John C. L. Wang Dr. Jim Stone ...
Sublimation temperature of circumstellar dust particles and its importance Hiroshi Kobayashi
... particles due to the P-R drag is proportional to β, their mass distribution is affected by the mass dependence η = −d ln β/d ln m. If the differential mass distribution of the dust source is proportional to m −b , that of drifting dust is modulated to m −b+η (e.g., Moro-Martı́n and Malhotra, 2003). ...
... particles due to the P-R drag is proportional to β, their mass distribution is affected by the mass dependence η = −d ln β/d ln m. If the differential mass distribution of the dust source is proportional to m −b , that of drifting dust is modulated to m −b+η (e.g., Moro-Martı́n and Malhotra, 2003). ...
The effects of disk building on the distributions of refractory materials
... the solar system, Ciesla (2010) concluded that this time corresponded to the point where the solar nebula was most massive, which would roughly be the transition phase from a class I to class II source in terms of the classification of young stellar objects (Lada and Wilking 1984; Lada and Shu 1990). ...
... the solar system, Ciesla (2010) concluded that this time corresponded to the point where the solar nebula was most massive, which would roughly be the transition phase from a class I to class II source in terms of the classification of young stellar objects (Lada and Wilking 1984; Lada and Shu 1990). ...
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... The solar atmosphere is full of dynamic phenomena. Solar flares, which are the most energetic explosive events in the solar system, are especially attractive because of their dynamic and beautiful appearance. They also stimulate our curiosity about the generation mechanism of such explosive events. ...
... The solar atmosphere is full of dynamic phenomena. Solar flares, which are the most energetic explosive events in the solar system, are especially attractive because of their dynamic and beautiful appearance. They also stimulate our curiosity about the generation mechanism of such explosive events. ...
chemical abundances for a-and f-type supergiant stars
... HD 45674, HD 180028, HD 194951 and HD 224893 is reported to be 83, 175, 82 and 145 respectively. This S/N per pixel has been derived for all spectra in the library at 5550 Å. HD 45674, HD 180028 and HD 194951 are objects labeled as IRAS point sources, (IRAS 06262 - 0032, IRAS 19122 + 0557 and IRAS ...
... HD 45674, HD 180028, HD 194951 and HD 224893 is reported to be 83, 175, 82 and 145 respectively. This S/N per pixel has been derived for all spectra in the library at 5550 Å. HD 45674, HD 180028 and HD 194951 are objects labeled as IRAS point sources, (IRAS 06262 - 0032, IRAS 19122 + 0557 and IRAS ...
Galactic Evolution of Silicon Isotopes: Applications to
... correlation with a slope of 0.46 instead of the _measured slope of 1.34. Neutron Ñuxes always produce more excess 30Si than 29Si because of their relative neutron capture cross sections, and because of the large 33S(n, a)30Si cross section (Bao & Kappeler 1987 ; Brown & Clayton 1992). This forces o ...
... correlation with a slope of 0.46 instead of the _measured slope of 1.34. Neutron Ñuxes always produce more excess 30Si than 29Si because of their relative neutron capture cross sections, and because of the large 33S(n, a)30Si cross section (Bao & Kappeler 1987 ; Brown & Clayton 1992). This forces o ...
Galactic Evolution of Silicon Isotopes: Application to Presolar SiC
... medium at distances and times appropriate to the birth of the solar system. Primarily we seek connections between evolution of the calculated silicon isotopic ratios and the anomalous silicon isotopic ratios found in presolar silicon carbide grains extracted from meteorites. Secondarily we assess co ...
... medium at distances and times appropriate to the birth of the solar system. Primarily we seek connections between evolution of the calculated silicon isotopic ratios and the anomalous silicon isotopic ratios found in presolar silicon carbide grains extracted from meteorites. Secondarily we assess co ...
- UCL Discovery
... The evolution of the Sun’s magnetic field with time is crucial to the understanding of solar activity, particularly in the context of the 11 year sunspot cycle. The Sun’s magnetic field undergoes an oscillation between a poloidal configuration at sunspot minimum and a toroidal configuration at sunsp ...
... The evolution of the Sun’s magnetic field with time is crucial to the understanding of solar activity, particularly in the context of the 11 year sunspot cycle. The Sun’s magnetic field undergoes an oscillation between a poloidal configuration at sunspot minimum and a toroidal configuration at sunsp ...
Simulating the outer layers of Procyon A: a comparison with the Sun
... heavy elements, which affect the radiative opacities sensitively, the precise helium abundance is a second-order effect in determining the structure and dynamics of the atmosphere. 2.2 The 3D simulation The 3D simulation of Procyon is a square-based box of dimensions 14 500 km × 14 500 km × 16 300 k ...
... heavy elements, which affect the radiative opacities sensitively, the precise helium abundance is a second-order effect in determining the structure and dynamics of the atmosphere. 2.2 The 3D simulation The 3D simulation of Procyon is a square-based box of dimensions 14 500 km × 14 500 km × 16 300 k ...
Simulating the outer layers of Procyon A: a comparison with the Sun
... Heavy element diffusion in the envelope is complicated by the fact that both radiative levitation of certain elements and turbulent mixing may also play an important role in inhibiting the gravitational settling (Richer et al. 1998). The Procyon atmosphere typifies the complex transition between the ...
... Heavy element diffusion in the envelope is complicated by the fact that both radiative levitation of certain elements and turbulent mixing may also play an important role in inhibiting the gravitational settling (Richer et al. 1998). The Procyon atmosphere typifies the complex transition between the ...
Influence of extreme ultraviolet radiation on the Pv ionization fraction
... Different diagnostics of hot star wind mass-loss rates provide results that are difficult to reconcile with each other. The widely accepted presence of clumping in hot star winds implies a significant reduction of observational mass-loss rate estimates from diagnostics that depend on the square of t ...
... Different diagnostics of hot star wind mass-loss rates provide results that are difficult to reconcile with each other. The widely accepted presence of clumping in hot star winds implies a significant reduction of observational mass-loss rate estimates from diagnostics that depend on the square of t ...
Plasma Diagnostics and Hydrodynamic Evolution of Solar Flares
... cooling model. The model is found to provide a well-defined lower limit to the observed cooling time of a flare, but does not well fit the distribution. The discrepancies between the model and observations are assumed to be due to additional heating which is then compared to the flares’ overall ther ...
... cooling model. The model is found to provide a well-defined lower limit to the observed cooling time of a flare, but does not well fit the distribution. The discrepancies between the model and observations are assumed to be due to additional heating which is then compared to the flares’ overall ther ...
Krypton in presolar mainstream SiC grains from AGB stars
... explain the high 130 Xe/82 Kr in fine grains. The results by Pignatari et al. (2004) seem to disagree with the second scenario. The Xe−G component in mainstream SiC grains does not agree with AGB models predictions at low metallicity (Z ≤ 1/3 Z ), because the (134 Xe/130 Xe)s ratio is too high with ...
... explain the high 130 Xe/82 Kr in fine grains. The results by Pignatari et al. (2004) seem to disagree with the second scenario. The Xe−G component in mainstream SiC grains does not agree with AGB models predictions at low metallicity (Z ≤ 1/3 Z ), because the (134 Xe/130 Xe)s ratio is too high with ...
Master`s Thesis
... This project arises from a previous research with positive results about detection of Solar flares by means of the overionization of the Earth’s ionosphere detected with global GPS measurements1. One of the co-authors of this project which is actually my project supervisor, Manuel Hernádez-Pajares, ...
... This project arises from a previous research with positive results about detection of Solar flares by means of the overionization of the Earth’s ionosphere detected with global GPS measurements1. One of the co-authors of this project which is actually my project supervisor, Manuel Hernádez-Pajares, ...
The X-ray emission from shock cooling zones in O star winds
... corresponds to a time dependence vf ∝ tδ−1 of the speed of all flow features, and a change in mass loss rate Ṁ ∝ tδ−1 of the source after throwing off the shell. This temporal behaviour of source conditions is meant to mimic a solar flare and the subsequent return to the quiescent wind. – However, ...
... corresponds to a time dependence vf ∝ tδ−1 of the speed of all flow features, and a change in mass loss rate Ṁ ∝ tδ−1 of the source after throwing off the shell. This temporal behaviour of source conditions is meant to mimic a solar flare and the subsequent return to the quiescent wind. – However, ...
Solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. This plasma consists of mostly electrons, protons and alpha particles with energies usually between 1.5 and 10 keV; embedded in the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar longitude. Its particles can escape the Sun's gravity because of their high energy, from the high temperature of the corona and magnetic, electrical and electromagnetic phenomena in it.The solar wind flows outward supersonically to great distances, filling a region known as the heliosphere, an enormous bubble-like volume surrounded by the interstellar medium. Other related phenomena include the aurora (northern and southern lights), the plasma tails of comets that always point away from the Sun, and geomagnetic storms that can change the direction of magnetic field lines and create strong currents in power grids on Earth.