Stellar dust production and composition in the Magellanic Clouds F. Kemper
... in the ISO spectroscopy, and found that, while the spectra all show amorphous silicates, some of them also show the spectral signature of Al2 O3 (alumina). The relative strength of the alumina signature to the spectrum decreases with increasing mass-loss rate, suggestive of a covering of the alumina ...
... in the ISO spectroscopy, and found that, while the spectra all show amorphous silicates, some of them also show the spectral signature of Al2 O3 (alumina). The relative strength of the alumina signature to the spectrum decreases with increasing mass-loss rate, suggestive of a covering of the alumina ...
Present-day cosmic abundances - Dr. Karl Remeis
... substantial for some chemical species. An ideal alternative to find a reference for the chemical composition of cosmic matter are normal unevolved early B-type stars of ∼8-18 M⊙ , which can provide simultaneously temporal (present-day) and local (birth place) information on chemical abundances. They ...
... substantial for some chemical species. An ideal alternative to find a reference for the chemical composition of cosmic matter are normal unevolved early B-type stars of ∼8-18 M⊙ , which can provide simultaneously temporal (present-day) and local (birth place) information on chemical abundances. They ...
Matter and antimatter in the same universe?
... The Dirac theory, and the successive generalizations, states that not only antiparticles exist, but also that they are created following the same rules of particles. This led to a new principle of symmetry in physics between matter and antimatter. In principle, to any reaction involving particles th ...
... The Dirac theory, and the successive generalizations, states that not only antiparticles exist, but also that they are created following the same rules of particles. This led to a new principle of symmetry in physics between matter and antimatter. In principle, to any reaction involving particles th ...
UV Irradiation of Polycyclic Aromatic Hydrocarbons in Ices
... of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis. In ...
... of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis. In ...
The AG Carinae nebula: abundant evidence for a red supergiant
... abundances are derived for five regions across the nebula from high spatial resolution spectroscopy obtained at the Anglo-Australian Telescope (AAT). We derive an average Te of 6350 ± 400 K, an ne of 820 ± 170 cm-3, and find that nitrogen (N) is enhanced by a factor of 4.5 ± 1.3 and that oxygen (0) ...
... abundances are derived for five regions across the nebula from high spatial resolution spectroscopy obtained at the Anglo-Australian Telescope (AAT). We derive an average Te of 6350 ± 400 K, an ne of 820 ± 170 cm-3, and find that nitrogen (N) is enhanced by a factor of 4.5 ± 1.3 and that oxygen (0) ...
The Universe
... Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In the Hubble classification scheme, spiral galaxies are listed as type S, followed by a letter (a, b, or c) ...
... Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In the Hubble classification scheme, spiral galaxies are listed as type S, followed by a letter (a, b, or c) ...
The Universe
... Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In the Hubble classification scheme, spiral galaxies are listed as type S, followed by a letter (a, b, or c) ...
... Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In the Hubble classification scheme, spiral galaxies are listed as type S, followed by a letter (a, b, or c) ...
205 Advances in Natural and Applied Sciences, 4(2): 205-209, 2010 ISSN 1995-0772
... neutron star or a black hole formed after collapse of an ordinary star) and a stellar companion, orbit each other at a distance small enough to enable mass transfer from the companion star to the compact object. The transferred matter spirals towards the compact object and forms an “accretion disk” ...
... neutron star or a black hole formed after collapse of an ordinary star) and a stellar companion, orbit each other at a distance small enough to enable mass transfer from the companion star to the compact object. The transferred matter spirals towards the compact object and forms an “accretion disk” ...
Stellar Metamorphosis
... therefore these stars should not be separate, but should have combined into a single larger star. It is suggested to the reader to realize that gravity theory is a failed theory [13] as it is not a force [14] and cannot accrete material what so ever. [15][16] These stars simply formed in different a ...
... therefore these stars should not be separate, but should have combined into a single larger star. It is suggested to the reader to realize that gravity theory is a failed theory [13] as it is not a force [14] and cannot accrete material what so ever. [15][16] These stars simply formed in different a ...
General Module information
... Explain why fusion of light nuclei releases energy in terms of the binding energy per nucleon and its dependence on atomic mass. Explain qualitatively what the “Gamow peak” is and why it occurs. Recognise the equations for the three reaction processes: the p-p reaction, the CNO cycle and the triple- ...
... Explain why fusion of light nuclei releases energy in terms of the binding energy per nucleon and its dependence on atomic mass. Explain qualitatively what the “Gamow peak” is and why it occurs. Recognise the equations for the three reaction processes: the p-p reaction, the CNO cycle and the triple- ...
PPT - GSI
... - Benchmark of theoretical saddle-point masses Investigation of the topographic theorem. Validation of Thomas-Fermi model and FRLDM model. - Development of a semi-empirical model for mass and charge division in fission Statistical macroscopic-microscopic approach. with schematic dynamical features a ...
... - Benchmark of theoretical saddle-point masses Investigation of the topographic theorem. Validation of Thomas-Fermi model and FRLDM model. - Development of a semi-empirical model for mass and charge division in fission Statistical macroscopic-microscopic approach. with schematic dynamical features a ...
Indroduction
... viewed as being formed by mergers of disk galaxies in a universe where structures are built through hierarchical clustering. In the local universe, ongoing merging is observed and it is generally assumed that most of the \ultra-luminous" IRAS galaxies represent merging process (Schweizer, 1990). In ...
... viewed as being formed by mergers of disk galaxies in a universe where structures are built through hierarchical clustering. In the local universe, ongoing merging is observed and it is generally assumed that most of the \ultra-luminous" IRAS galaxies represent merging process (Schweizer, 1990). In ...
THE YELLOW SUPERGIANT PROGENITOR OF THE TYPE II
... provide definitive detections of progenitor stars on images of galaxies gathered before explosion (for a review, see Smartt 2009). The luminosity and inferred mass of progenitors give an insight into the origin of the SN types, the last stages of stellar evolution, and the initial conditions of the ...
... provide definitive detections of progenitor stars on images of galaxies gathered before explosion (for a review, see Smartt 2009). The luminosity and inferred mass of progenitors give an insight into the origin of the SN types, the last stages of stellar evolution, and the initial conditions of the ...
The age structure of the Milky Way`s halo
... then became part of the main galaxy halo by merging and accretion (accreted stars), while others were born from infalling gas mainly associated with progenitor galaxies (in situ stars)42-44. The chemical evolution of lower-mass fragments is expected to be truncated due to either the consumption of a ...
... then became part of the main galaxy halo by merging and accretion (accreted stars), while others were born from infalling gas mainly associated with progenitor galaxies (in situ stars)42-44. The chemical evolution of lower-mass fragments is expected to be truncated due to either the consumption of a ...
Star counts in the Galaxy-Simulating from very deep to very shallow
... be derived, for instance, starting from an initial mass function (IMF), an age-metallicity relation (AMR), and a law for the star formation rate (SFR) as a function of Galaxy age. In the present paper, we will describe a Galaxy model developed according to the population synthesis approach, taking p ...
... be derived, for instance, starting from an initial mass function (IMF), an age-metallicity relation (AMR), and a law for the star formation rate (SFR) as a function of Galaxy age. In the present paper, we will describe a Galaxy model developed according to the population synthesis approach, taking p ...
Chemical abundances of metal-poor RR Lyrae stars in the Magellanic Clouds
... In galaxies that experienced star formation throughout cosmic history, the identification of purely old populations is difficult. For instance, the abundant red giants can cover an age range of more than ten Gyr. Thus one can either turn to globular clusters as easily identifiable and reliably age-d ...
... In galaxies that experienced star formation throughout cosmic history, the identification of purely old populations is difficult. For instance, the abundant red giants can cover an age range of more than ten Gyr. Thus one can either turn to globular clusters as easily identifiable and reliably age-d ...
Detection of isolated population III stars with the James Webb Space
... (1995) model to modify the radiation below the Lyα-line at z < 6. Even though Lyα is the main absorbing mechanism the model also takes higher order Lyman-absorbers into account. We use the average absorption predicted by the model. The very high effective temperature of a population III star (∼ 100, ...
... (1995) model to modify the radiation below the Lyα-line at z < 6. Even though Lyα is the main absorbing mechanism the model also takes higher order Lyman-absorbers into account. We use the average absorption predicted by the model. The very high effective temperature of a population III star (∼ 100, ...
The chemical composition of solar-type stars and its impact on the
... We illuminate the connection between the chemical abundance ratios in stellar atmospheres and the presence of planets around the respective stars. In order to obtain reliable results, we consider only solar-type stars and conduct spectroscopic parameter and abundance analyzes in a strictly different ...
... We illuminate the connection between the chemical abundance ratios in stellar atmospheres and the presence of planets around the respective stars. In order to obtain reliable results, we consider only solar-type stars and conduct spectroscopic parameter and abundance analyzes in a strictly different ...
The Milky Way galaxy Contents Summary
... by galaxies that lie just below the top of the scale. The Sun lies in just such a galaxy, the Milky Way galaxy. Galaxies can usefully be considered to be made up of two components: a spheroid and a disc (Figure 1). The spheroid is made up of stars that move around in a disorganised way, rather like ...
... by galaxies that lie just below the top of the scale. The Sun lies in just such a galaxy, the Milky Way galaxy. Galaxies can usefully be considered to be made up of two components: a spheroid and a disc (Figure 1). The spheroid is made up of stars that move around in a disorganised way, rather like ...
Population synthesis of Be/white dwarf binaries in the Galaxy
... of a compact companion are absorbed by the Be star envelope. The detection of a white dwarf is possible during the period when the Be star disc-like envelope is lacking by the detection of white dwarf extreme-UV and soft X-ray emission. This method of registration appears to be particularly promisin ...
... of a compact companion are absorbed by the Be star envelope. The detection of a white dwarf is possible during the period when the Be star disc-like envelope is lacking by the detection of white dwarf extreme-UV and soft X-ray emission. This method of registration appears to be particularly promisin ...
Asymptotic Giant Branch stars viewed up-close and far-off
... The asymptotic giant branch (AGB) is the last stage of stellar evolution for stars with masses between ≈0.8–8 M⊙ . This phase is characterised by an intense mass loss, which builds up a circumstellar envelope (CSE) of dust and gas. It is through this process that the AGB stars contribute to the chem ...
... The asymptotic giant branch (AGB) is the last stage of stellar evolution for stars with masses between ≈0.8–8 M⊙ . This phase is characterised by an intense mass loss, which builds up a circumstellar envelope (CSE) of dust and gas. It is through this process that the AGB stars contribute to the chem ...
Gamma - Ray Observations of Olaf Reimer
... X-Ray Binaries as Gamma-Ray Sources Binary systems of a compact object (neutron star or black hole) and a stellar companion Matter is flowing over from the stellar companion onto the compact object. Angular momentum conservation => Formation of an accretion disk Matter in the accretion disk heats u ...
... X-Ray Binaries as Gamma-Ray Sources Binary systems of a compact object (neutron star or black hole) and a stellar companion Matter is flowing over from the stellar companion onto the compact object. Angular momentum conservation => Formation of an accretion disk Matter in the accretion disk heats u ...
Reprocessing the Hipparcos data of evolved stars
... improved astrometric fits and chromaticity corrections. The K band magnitudes are taken from the literature and from measurements by COBE, and are corrected for interstellar and circumstellar extinction. The sample contains stars of several spectral types: M, S and C, and of several variability clas ...
... improved astrometric fits and chromaticity corrections. The K band magnitudes are taken from the literature and from measurements by COBE, and are corrected for interstellar and circumstellar extinction. The sample contains stars of several spectral types: M, S and C, and of several variability clas ...
Search for giant planets in M67 III: excess of Hot Jupiters in dense
... Hot Jupiters (HJs) are defined as giant planets (M p > 0.3MJup ) in short period orbits (P < 10 days). They show an occurance rate of ∼1.2% around Sun-like field stars (Wright et al. 2012; Mayor et al. 2011). These close-in giant planets are highly unlikely to have formed in situ and it is believed ...
... Hot Jupiters (HJs) are defined as giant planets (M p > 0.3MJup ) in short period orbits (P < 10 days). They show an occurance rate of ∼1.2% around Sun-like field stars (Wright et al. 2012; Mayor et al. 2011). These close-in giant planets are highly unlikely to have formed in situ and it is believed ...
Nucleosynthesis
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons. The first nuclei were formed about three minutes after the Big Bang, through the process called Big Bang nucleosynthesis. It was then that hydrogen and helium formed to become the content of the first stars, and this primeval process is responsible for the present hydrogen/helium ratio of the cosmos.With the formation of stars, heavier nuclei were created from hydrogen and helium by stellar nucleosynthesis, a process that continues today. Some of these elements, particularly those lighter than iron, continue to be delivered to the interstellar medium when low mass stars eject their outer envelope before they collapse to form white dwarfs. The remains of their ejected mass form the planetary nebulae observable throughout our galaxy.Supernova nucleosynthesis within exploding stars by fusing carbon and oxygen is responsible for the abundances of elements between magnesium (atomic number 12) and nickel (atomic number 28). Supernova nucleosynthesis is also thought to be responsible for the creation of rarer elements heavier than iron and nickel, in the last few seconds of a type II supernova event. The synthesis of these heavier elements absorbs energy (endothermic) as they are created, from the energy produced during the supernova explosion. Some of those elements are created from the absorption of multiple neutrons (the R process) in the period of a few seconds during the explosion. The elements formed in supernovas include the heaviest elements known, such as the long-lived elements uranium and thorium.Cosmic ray spallation, caused when cosmic rays impact the interstellar medium and fragment larger atomic species, is a significant source of the lighter nuclei, particularly 3He, 9Be and 10,11B, that are not created by stellar nucleosynthesis.In addition to the fusion processes responsible for the growing abundances of elements in the universe, a few minor natural processes continue to produce very small numbers of new nuclides on Earth. These nuclides contribute little to their abundances, but may account for the presence of specific new nuclei. These nuclides are produced via radiogenesis (decay) of long-lived, heavy, primordial radionuclides such as uranium and thorium. Cosmic ray bombardment of elements on Earth also contribute to the presence of rare, short-lived atomic species called cosmogenic nuclides.