CH15.AST1001.S15.EDS
... • Atomic hydrogen (H) gas forms as hot gas cools, allowing electrons to join with protons. Atomic hydrogen is observed by radio telescopes in the 21 cm emission line. • Molecular clouds (H2) form next, after gas cools enough to allow atoms to combine into molecules. Molecular hydrogen is difficult ...
... • Atomic hydrogen (H) gas forms as hot gas cools, allowing electrons to join with protons. Atomic hydrogen is observed by radio telescopes in the 21 cm emission line. • Molecular clouds (H2) form next, after gas cools enough to allow atoms to combine into molecules. Molecular hydrogen is difficult ...
Episode 705: Cosmology - Teaching Advanced Physics
... This exercise is intended to give practice in converting Hubble’s constant to an age of the Universe. It is important for students to understand the connection between this constant and the age of the Universe, and this point will need careful explanation for some students. Important points can also ...
... This exercise is intended to give practice in converting Hubble’s constant to an age of the Universe. It is important for students to understand the connection between this constant and the age of the Universe, and this point will need careful explanation for some students. Important points can also ...
Word version of Episode 705
... This exercise is intended to give practice in converting Hubble’s constant to an age of the Universe. It is important for students to understand the connection between this constant and the age of the Universe, and this point will need careful explanation for some students. Important points can also ...
... This exercise is intended to give practice in converting Hubble’s constant to an age of the Universe. It is important for students to understand the connection between this constant and the age of the Universe, and this point will need careful explanation for some students. Important points can also ...
Chemical composition of cosmic dust in the solar vicinity
... - comparison with Orion dust: graphite minor species ► C in PAHs - homogeneity over hundreds of parsecs: highly efficient mixing Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 ...
... - comparison with Orion dust: graphite minor species ► C in PAHs - homogeneity over hundreds of parsecs: highly efficient mixing Multiple phases IS Dust (ISM-SPP) Garching– 15.09.2016 ...
LIAC_VanGrootel - ORBi
... i.e., stars that experience a delayed He-flash during contraction, at higher Teff, after leaving the RGB before tip (H-burning shell stops due to strong mass loss on RGB) D’Cruz et al. (1996) showed that such stars populate the EHB, with similar ...
... i.e., stars that experience a delayed He-flash during contraction, at higher Teff, after leaving the RGB before tip (H-burning shell stops due to strong mass loss on RGB) D’Cruz et al. (1996) showed that such stars populate the EHB, with similar ...
The formation and evolution of galaxies
... • Overcooling leads to the formation of hundreds more small galaxies than are observed. ...
... • Overcooling leads to the formation of hundreds more small galaxies than are observed. ...
Article PDF - IOPscience
... components in this galaxy from the spectroscopy alone. The methodologically independent discovery of two distinct stellar components in CVn I from the LBC photometry and the much smaller extent of the young population surprisingly recalls their findings. A direct comparison of their spectroscopic sa ...
... components in this galaxy from the spectroscopy alone. The methodologically independent discovery of two distinct stellar components in CVn I from the LBC photometry and the much smaller extent of the young population surprisingly recalls their findings. A direct comparison of their spectroscopic sa ...
Stellar Relaxation Times
... center of the Galaxy is not gravitationally affected by other stars. On the other hand, giant molecular clouds have masses that are ~ 108 M. Although the number density of clouds is lower, it’s not 1016 times lower! The masses of these clouds are therefore high enough to scatter stars out of their ...
... center of the Galaxy is not gravitationally affected by other stars. On the other hand, giant molecular clouds have masses that are ~ 108 M. Although the number density of clouds is lower, it’s not 1016 times lower! The masses of these clouds are therefore high enough to scatter stars out of their ...
Dark Matter Capture in the first stars
... • Dark Matter (DM) in proto-stellar haloes can dramatically alter the formation of the first stars • The LSP (lightest supersymmetric particle) provides a heat source that prevents the protostar from further collapse, leading to a new stellar phase: • The first stars in the universe are giant (> 1 A ...
... • Dark Matter (DM) in proto-stellar haloes can dramatically alter the formation of the first stars • The LSP (lightest supersymmetric particle) provides a heat source that prevents the protostar from further collapse, leading to a new stellar phase: • The first stars in the universe are giant (> 1 A ...
Read more - University of Central Lancashire
... Most likely yes. The Kepler Space telescope has found planets that are very very similar to Earth so it’s just a matter of time until we find one just like Earth. What do you think the straight walls on asteroids are? Asteroids come in many different sizes and travel from all over the Solar System a ...
... Most likely yes. The Kepler Space telescope has found planets that are very very similar to Earth so it’s just a matter of time until we find one just like Earth. What do you think the straight walls on asteroids are? Asteroids come in many different sizes and travel from all over the Solar System a ...
PDF only
... to the nature of the companion star in the system (from Ref. [3-b]). (b) Measured surface temperatures of isolated neutron stars; the ages reported in abscissa are obtained from the rotating dipole model, and the solid line represents a standard cooling simulation (from Ref. [6-b]). We thus see how ...
... to the nature of the companion star in the system (from Ref. [3-b]). (b) Measured surface temperatures of isolated neutron stars; the ages reported in abscissa are obtained from the rotating dipole model, and the solid line represents a standard cooling simulation (from Ref. [6-b]). We thus see how ...
Turbulent convection in stellar interiors
... • Energy transport processes: • Photons diffusion (radiative zone) ...
... • Energy transport processes: • Photons diffusion (radiative zone) ...
Key paper.
... manuscript in preparation), we derive best-fit values for MD and b of (0:05 6 0:01ÞM ( and 1:0 6 0:2, respectively. We conclude that the true disk mass is a few per cent of a solar mass rather than the very low value derived from the CO line intensity. The opacity index, b, is significantly less tha ...
... manuscript in preparation), we derive best-fit values for MD and b of (0:05 6 0:01ÞM ( and 1:0 6 0:2, respectively. We conclude that the true disk mass is a few per cent of a solar mass rather than the very low value derived from the CO line intensity. The opacity index, b, is significantly less tha ...
Cosmic Rays
... generally from within our Milky Way galaxy. GCRs are atomic nuclei from which all of the surrounding electrons have been stripped away during their high-speed passage through the galaxy. They have probably been accelerated within the last few million years, and have traveled many times across th ...
... generally from within our Milky Way galaxy. GCRs are atomic nuclei from which all of the surrounding electrons have been stripped away during their high-speed passage through the galaxy. They have probably been accelerated within the last few million years, and have traveled many times across th ...
The Carina Dwarf Spheroidal Galaxy: A Goldmine for Cosmology
... vations, standard errors no larger than 0.02 mag and no evidence of intrinsic variation in excess of 0.05 mag rms when data from all filters are considered. These new comparisons show a few significant photometric outliers with magnitude differences > 0.10 mag, as expected in any large body of raw d ...
... vations, standard errors no larger than 0.02 mag and no evidence of intrinsic variation in excess of 0.05 mag rms when data from all filters are considered. These new comparisons show a few significant photometric outliers with magnitude differences > 0.10 mag, as expected in any large body of raw d ...
Journal of Theoretics MODELS OF THE ATOMIC NUCLEI
... the protons on the surface of the nucleus. Similar charges of the protons exclude the nucleus structure, in which the protons touch each other. Nature builds the nucleus in such a way that a neutron should be between the protons. As it is difficult to meet the last requirement when there are many pr ...
... the protons on the surface of the nucleus. Similar charges of the protons exclude the nucleus structure, in which the protons touch each other. Nature builds the nucleus in such a way that a neutron should be between the protons. As it is difficult to meet the last requirement when there are many pr ...
gravitational collapse to black holes
... For both reasons, it is clear that the iron core cannot exist forever, and will collapse under its own weight ...
... For both reasons, it is clear that the iron core cannot exist forever, and will collapse under its own weight ...
Measuring the Masses of Neutron Stars
... The compact remnants of massive stars A neutron star is the compact remnant of a massive star (M ≥ 8 MA) with a central density that can be as high as 5 to 10 times the density of an atomic nucleus. Neutron stars can be detected as radio sources (radio pulsars) or, when they accrete matter coming fr ...
... The compact remnants of massive stars A neutron star is the compact remnant of a massive star (M ≥ 8 MA) with a central density that can be as high as 5 to 10 times the density of an atomic nucleus. Neutron stars can be detected as radio sources (radio pulsars) or, when they accrete matter coming fr ...
Ultra faint dwarfs: probing early cosmic star formation
... of gas, mechanical feedback has negligible effects, and they evolve as a closed-box. As essentially all metals are retained they have a relatively high Fe-abundance which is seen as an almost inverted Fe-L relation below L = 104.5 L⊙ . Second UFs have extremely large M/L > 100 ratios, and the fainte ...
... of gas, mechanical feedback has negligible effects, and they evolve as a closed-box. As essentially all metals are retained they have a relatively high Fe-abundance which is seen as an almost inverted Fe-L relation below L = 104.5 L⊙ . Second UFs have extremely large M/L > 100 ratios, and the fainte ...
Chapter 8
... 8.1 Star formation and pre-main sequence evolution The process of star formation constitutes one of the main problems of modern astrophysics. Compared to our understanding of what happens after stars have formed out of the interstellar medium – that is, stellar evolution – star formation is a very i ...
... 8.1 Star formation and pre-main sequence evolution The process of star formation constitutes one of the main problems of modern astrophysics. Compared to our understanding of what happens after stars have formed out of the interstellar medium – that is, stellar evolution – star formation is a very i ...
Chapter 7 Stellar models and stellar stability
... as an initial condition. This is the case if one considers pre-main sequence stars. Fortunately, as we shall see later, in this case there is also a simplifying circumstance: pre-main sequence stars start out as fully convective gas spheres. This means that their temperature and pressure stratificat ...
... as an initial condition. This is the case if one considers pre-main sequence stars. Fortunately, as we shall see later, in this case there is also a simplifying circumstance: pre-main sequence stars start out as fully convective gas spheres. This means that their temperature and pressure stratificat ...
The evolution and explosion of massive stars
... the evolution of the universe. They light up regions of stellar birth and create the elements necessary to life. In their explosions, they produce spectacular fireworks and leave as remnants exotic objects—neutron stars and black holes. Their winds and radiation stir the interstellar medium and may ...
... the evolution of the universe. They light up regions of stellar birth and create the elements necessary to life. In their explosions, they produce spectacular fireworks and leave as remnants exotic objects—neutron stars and black holes. Their winds and radiation stir the interstellar medium and may ...
Chapter 5 Stellar Energy Production
... Examination of the curve of binding energy suggests two potential nuclear sources of energy: • Fission of heavier elements into lighter elements. • Fusion of lighter elements into heavier ones. Since stars are composed mostly of hydrogen and helium, • It is clear that their primary energy source mus ...
... Examination of the curve of binding energy suggests two potential nuclear sources of energy: • Fission of heavier elements into lighter elements. • Fusion of lighter elements into heavier ones. Since stars are composed mostly of hydrogen and helium, • It is clear that their primary energy source mus ...
The chemical composition of two supergiants in the dwarf
... in any other environment which has had a different star formation history.” The analysis of bright nebular emission lines of H II regions (and some PN) has been the most frequent approach to modeling the chemical evolution of galaxies to date (see Pagel 1997), and yet only a limited number of elemen ...
... in any other environment which has had a different star formation history.” The analysis of bright nebular emission lines of H II regions (and some PN) has been the most frequent approach to modeling the chemical evolution of galaxies to date (see Pagel 1997), and yet only a limited number of elemen ...
CORONAL EVOLUTION OF THE SUN IN TIME: HIGH
... spectroscopy and photometry with XMM-Newton. Six nearby main-sequence G stars with ages between 0.1 and 1.6 Gyr and rotation periods between 1 and 12.4 days have been observed. We use the X-ray spectra to derive coronal element abundances of C, N, O, Ne, Mg, Si, S, and Fe and the coronal emission ...
... spectroscopy and photometry with XMM-Newton. Six nearby main-sequence G stars with ages between 0.1 and 1.6 Gyr and rotation periods between 1 and 12.4 days have been observed. We use the X-ray spectra to derive coronal element abundances of C, N, O, Ne, Mg, Si, S, and Fe and the coronal emission ...
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.