Hot DQ White Dwarfs: Something Different
... by a thin envelope of helium (and hydrogen) that has survived the nuclear burning and mass loss phase. The core, which is essentially the result of the fusion of light elements, has a composition that depends on the initial mass of the star. For very low mass stars that could not ignite helium, it i ...
... by a thin envelope of helium (and hydrogen) that has survived the nuclear burning and mass loss phase. The core, which is essentially the result of the fusion of light elements, has a composition that depends on the initial mass of the star. For very low mass stars that could not ignite helium, it i ...
Theory of Motion of Matter on the Formation of Galaxy and Star
... As primordial galaxy nebula and primordial stellar nebula are vortex type, centrifugal effect makes dispersed matter unable to move rapidly towards nebula center. It produced relative motion between matter moving outwards primordial galaxy nebula center high density nuclear zone and dispersed matter ...
... As primordial galaxy nebula and primordial stellar nebula are vortex type, centrifugal effect makes dispersed matter unable to move rapidly towards nebula center. It produced relative motion between matter moving outwards primordial galaxy nebula center high density nuclear zone and dispersed matter ...
Document
... A disc-like structure with a center 100-150 pc from the Sun Inclined respect to the galactic plane by ~20o 2/3 of massive stars in 600 pc from the Sun belong to the Belt ...
... A disc-like structure with a center 100-150 pc from the Sun Inclined respect to the galactic plane by ~20o 2/3 of massive stars in 600 pc from the Sun belong to the Belt ...
Document
... A disc-like structure with a center 100-150 pc from the Sun Inclined respect to the galactic plane by ~20o 2/3 of massive stars in 600 pc from the Sun belong to the Belt ...
... A disc-like structure with a center 100-150 pc from the Sun Inclined respect to the galactic plane by ~20o 2/3 of massive stars in 600 pc from the Sun belong to the Belt ...
A Digital Spectral Classification Atlas
... autonomy of the system as well as ensuring that different observers will classify stars on the same system. When the MK system was first defined, it was based on photographic spectra in the blue-violet part of the spectrum. This was done by necessity, as scientific photographic emulsions in the 1940 ...
... autonomy of the system as well as ensuring that different observers will classify stars on the same system. When the MK system was first defined, it was based on photographic spectra in the blue-violet part of the spectrum. This was done by necessity, as scientific photographic emulsions in the 1940 ...
the first three thresholds - McGraw
... again to form a new universe (see Chapter 13). Another speculation, which is now taken more seriously, is that there is a vast multidimensional “multiverse” within which universes keep appearing, each with its own distinctive features, so that our universe may be one of countless billions of univers ...
... again to form a new universe (see Chapter 13). Another speculation, which is now taken more seriously, is that there is a vast multidimensional “multiverse” within which universes keep appearing, each with its own distinctive features, so that our universe may be one of countless billions of univers ...
Document
... deceleration in the direction of motion and an expansion in directions perpendicular to the flow 3- The cloud shows an abundance gradient : metal depletion increases steadily from the rear of the cloud to the apex 4- The cloud is in interaction with its surrounding: * evidence for a shock progressin ...
... deceleration in the direction of motion and an expansion in directions perpendicular to the flow 3- The cloud shows an abundance gradient : metal depletion increases steadily from the rear of the cloud to the apex 4- The cloud is in interaction with its surrounding: * evidence for a shock progressin ...
Lives of Stars - McDonald Observatory
... SOL: I was out of helium in the core. My core was mostly carbon, surrounded by a shell of fusing helium, and an outer shell of fusing hydrogen. My inside was like an onion with lots of layers! The core collapsed further, with little to support it against its weight. Since it was so small and massive ...
... SOL: I was out of helium in the core. My core was mostly carbon, surrounded by a shell of fusing helium, and an outer shell of fusing hydrogen. My inside was like an onion with lots of layers! The core collapsed further, with little to support it against its weight. Since it was so small and massive ...
Chapter 5 Theory of Stellar Evolution
... concentrate on what is known with some certainty. Thus, we assume that stars can contract out of the interstellar medium, and generally we avoid most of the detailed description of the final, fatal collapse of massive stars. In addition, the fascinating field of the evolution of close binary stars, ...
... concentrate on what is known with some certainty. Thus, we assume that stars can contract out of the interstellar medium, and generally we avoid most of the detailed description of the final, fatal collapse of massive stars. In addition, the fascinating field of the evolution of close binary stars, ...
THE DAWN OF X-RAY ASTRONOMY
... emitted x-rays at the same rate as the Sun, we would expect fluxes at earth as small as 10-4 photons cm-2s-1. Other possible sources, such as supernova remnants, flare stars, peculiar A stars, etc., were considered, and great uncertainty had to be assigned to the estimates of their x-ray fluxes. It ...
... emitted x-rays at the same rate as the Sun, we would expect fluxes at earth as small as 10-4 photons cm-2s-1. Other possible sources, such as supernova remnants, flare stars, peculiar A stars, etc., were considered, and great uncertainty had to be assigned to the estimates of their x-ray fluxes. It ...
The Pleiades in the Salle des Taureaux", Grotte de Lascaux
... the oldest traditions, for example from the nomenclature in the Almanac of Fig. 4 The copperplate engraving VII from Bode, 1805. The figure of the Klaudios Ptolemaios2 (ERREN, 1967: constellation looks like the rock picture of the aurochs no. 18 in the "Salle des 320; KUNITZSCH, 1974: 268-269, 271); ...
... the oldest traditions, for example from the nomenclature in the Almanac of Fig. 4 The copperplate engraving VII from Bode, 1805. The figure of the Klaudios Ptolemaios2 (ERREN, 1967: constellation looks like the rock picture of the aurochs no. 18 in the "Salle des 320; KUNITZSCH, 1974: 268-269, 271); ...
astronomy (astr)
... Permission of the instructor. One-week field experience at the National Radio Astronomy Observatory in Green Bank, WV, for experiential education (EE) credit. Observing with radio telescopes and antennae: supernova remnants, star-forming regions, normal and active galaxies, quasars, solar system obj ...
... Permission of the instructor. One-week field experience at the National Radio Astronomy Observatory in Green Bank, WV, for experiential education (EE) credit. Observing with radio telescopes and antennae: supernova remnants, star-forming regions, normal and active galaxies, quasars, solar system obj ...
Giant Low Surface Brightness Galaxies
... on GLSB galaxies; their nuclear and disk properties are very distinct from the LSB dwarf galaxies or smaller LSB disk galaxies. Apart from their rather exotic and rare nature, GLSB galaxies provide an interesting sample to study how massive dark matter halos can affect star formation and even nuclea ...
... on GLSB galaxies; their nuclear and disk properties are very distinct from the LSB dwarf galaxies or smaller LSB disk galaxies. Apart from their rather exotic and rare nature, GLSB galaxies provide an interesting sample to study how massive dark matter halos can affect star formation and even nuclea ...
A Search for Exozodiacal Dust and Faint Companions near Sirius
... b Pictoris, the presence of warm dust is inferred from analysis of a silicate emission feature at 10 km (Telesco & Knacke 1991 ; Knacke et al. 1993). Others, like the disk around HR 4796, show marginally resolved emission at 10 km that is interpreted as exozodiacal (Koerner et al. 1998). Dust clouds ...
... b Pictoris, the presence of warm dust is inferred from analysis of a silicate emission feature at 10 km (Telesco & Knacke 1991 ; Knacke et al. 1993). Others, like the disk around HR 4796, show marginally resolved emission at 10 km that is interpreted as exozodiacal (Koerner et al. 1998). Dust clouds ...
The Sun
... to be stable. Earth's magnetic field reverses ~ every million years. The Sun's magnetic field is generated close to the surface. The magnetic field is dragged with the Sun's differential rotation, and it will wind up. ...
... to be stable. Earth's magnetic field reverses ~ every million years. The Sun's magnetic field is generated close to the surface. The magnetic field is dragged with the Sun's differential rotation, and it will wind up. ...
NAS biographical memoir of Martin Schwarzschild
... the simple knowledge of the mass, radius, and luminosity of the sun—along with the recently discovered work by Bethe on nuclear-energy generation—allowed a determination of the solar helium content. Helium is rare on earth, and it was a bit of a surprise when this first calculation of the interior c ...
... the simple knowledge of the mass, radius, and luminosity of the sun—along with the recently discovered work by Bethe on nuclear-energy generation—allowed a determination of the solar helium content. Helium is rare on earth, and it was a bit of a surprise when this first calculation of the interior c ...
MOLECULAR CLOUDS 1. Introduction
... for the CO to lie in spiral arms. The optical image shows no large scale spiral structure at all, though near infrared images show weak underlying spiral arms (Thornley 1996). Nevertheless NGC 5055 does show evidence for spirality, short incoherent spiral arm segments that may play a role in GMC for ...
... for the CO to lie in spiral arms. The optical image shows no large scale spiral structure at all, though near infrared images show weak underlying spiral arms (Thornley 1996). Nevertheless NGC 5055 does show evidence for spirality, short incoherent spiral arm segments that may play a role in GMC for ...
Chapter 10 Formation and evolution of the Local Group
... Summary: The Local Group (LG) is the group of galaxies gravitationally associated with the Galaxy and M 31. Galaxies within the LG have overcome the general expansion of the universe. There are approximately 75 galaxies in the LG within a diameter of ∼3 Mpc having a total mass of 2-5 × 1012 M⊙ . A s ...
... Summary: The Local Group (LG) is the group of galaxies gravitationally associated with the Galaxy and M 31. Galaxies within the LG have overcome the general expansion of the universe. There are approximately 75 galaxies in the LG within a diameter of ∼3 Mpc having a total mass of 2-5 × 1012 M⊙ . A s ...
An Unbiased Near-infrared Interferometric Survey for Hot
... evolution of extrasolar planetary systems. However, debris discs that are relatively easy to detect are located several astronomical units (au) to a few hundreds of au from their host stars, and thus only trace the outer regions of planetary systems. In order to study the inner regions close to the ...
... evolution of extrasolar planetary systems. However, debris discs that are relatively easy to detect are located several astronomical units (au) to a few hundreds of au from their host stars, and thus only trace the outer regions of planetary systems. In order to study the inner regions close to the ...
Planck early results. XIX. All-sky temperature and dust optical depth
... To measure the amount and distribution of the molecular ISM, as well as the cold atomic ISM, other tracers of the interstellar gas are required. At least three tracers have been used in the past. These are UV absorption in Werner bands of H2 , infrared emission from dust, and γ-ray emission from pio ...
... To measure the amount and distribution of the molecular ISM, as well as the cold atomic ISM, other tracers of the interstellar gas are required. At least three tracers have been used in the past. These are UV absorption in Werner bands of H2 , infrared emission from dust, and γ-ray emission from pio ...
1 Cosmology: a brief refresher course
... there are still too many extremely high energy photons around, and these photodisintegrate any heavy nuclei that form. As the Universe expands and cools, however, the number density of these photons falls off exponentially, and once the temperature is kT ' 80 keV, heavier nuclei start to form in abu ...
... there are still too many extremely high energy photons around, and these photodisintegrate any heavy nuclei that form. As the Universe expands and cools, however, the number density of these photons falls off exponentially, and once the temperature is kT ' 80 keV, heavier nuclei start to form in abu ...
arXiv:astro-ph/0508448v1 22 Aug 2005
... massive enough to collapse to a black hole rather than a neutron star (Fryer 1999, van den Heuvel et al. 2000). The level of wind ...
... massive enough to collapse to a black hole rather than a neutron star (Fryer 1999, van den Heuvel et al. 2000). The level of wind ...
Supernovae - University of Texas Astronomy Home Page
... question under active investigation). If we consider stars with mass in excess of about 20 solar masses, we find such stars are born, and hence die, too infrequently to account for the rate at which Type II supernovae explode. If we consider stars with less than about 8 solar masses, we find that su ...
... question under active investigation). If we consider stars with mass in excess of about 20 solar masses, we find such stars are born, and hence die, too infrequently to account for the rate at which Type II supernovae explode. If we consider stars with less than about 8 solar masses, we find that su ...
Objective Classification of Galaxy Spectra using the Information Bottleneck Method
... break the ensemble into classes it requires a further step based on a training set (e.g. Bromley et al. 1998, Folkes et al. 1999). Unlike PCA, the information bottleneck (IB) method presented here is non-linear, and it naturally yields a principled partitioning of the galaxies into classes. These cl ...
... break the ensemble into classes it requires a further step based on a training set (e.g. Bromley et al. 1998, Folkes et al. 1999). Unlike PCA, the information bottleneck (IB) method presented here is non-linear, and it naturally yields a principled partitioning of the galaxies into classes. These cl ...
Rotation Periods of Wide Binaries in the Kepler Field
... index are available in the archive for all but a few of the CPM stars. Furthermore, the color index, (gKIC − Ks ), has good sensitivity to stellar temperature over a wide range of spectral types and is widely available in various stellar archives. In the following, I will refer to these indices as “ ...
... index are available in the archive for all but a few of the CPM stars. Furthermore, the color index, (gKIC − Ks ), has good sensitivity to stellar temperature over a wide range of spectral types and is widely available in various stellar archives. In the following, I will refer to these indices as “ ...
H II region
An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived blue stars forged in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas. H II regions—sometimes several hundred light-years across—are often associated with giant molecular clouds. The first known H II region was the Orion Nebula, which was discovered in 1610 by Nicolas-Claude Fabri de Peiresc.H II regions are named for the large amount of ionised atomic hydrogen they contain, referred to as H II, pronounced H-two by astronomers (an H I region being neutral atomic hydrogen, and H2 being molecular hydrogen). Such regions have extremely diverse shapes, because the distribution of the stars and gas inside them is irregular. They often appear clumpy and filamentary, sometimes showing bizarre shapes such as the Horsehead Nebula. H II regions may give birth to thousands of stars over a period of several million years. In the end, supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster will disperse the gases of the H II region, leaving behind a cluster of birthed stars such as the Pleiades.H II regions can be seen to considerable distances in the universe, and the study of extragalactic H II regions is important in determining the distance and chemical composition of other galaxies. Spiral and irregular galaxies contain many H II regions, while elliptical galaxies are almost devoid of them. In the spiral galaxies, including the Milky Way, H II regions are concentrated in the spiral arms, while in the irregular galaxies they are distributed chaotically. Some galaxies contain huge H II regions, which may contain tens of thousands of stars. Examples include the 30 Doradus region in the Large Magellanic Cloud and NGC 604 in the Triangulum Galaxy.