AST1100 Lecture Notes
... Several stars show periodic changes in their apparent magnitudes. This was first thought to be caused by dark spots on a rotating star’s surface: When the dark spots were turned towards us, the star appeared fainter, when the spots were turned away from us, the star appeared brighter. Today we know ...
... Several stars show periodic changes in their apparent magnitudes. This was first thought to be caused by dark spots on a rotating star’s surface: When the dark spots were turned towards us, the star appeared fainter, when the spots were turned away from us, the star appeared brighter. Today we know ...
The Life of the Sun
... drifts away. At this point you now have a hot cinder of a Star. That cinder of a Star collapses down. It no longer has any burning going on to support the Atoms against one another. As they collapse they actually reach a degenerate gas phase. This is where the Hydrogen and Helium Atoms pack themselv ...
... drifts away. At this point you now have a hot cinder of a Star. That cinder of a Star collapses down. It no longer has any burning going on to support the Atoms against one another. As they collapse they actually reach a degenerate gas phase. This is where the Hydrogen and Helium Atoms pack themselv ...
Astr 102 Lec 6: Basic Properties of Stars
... Questions of the Day • What are density, temperature, and pressure, and how are they related? • What is the difference between luminosity ...
... Questions of the Day • What are density, temperature, and pressure, and how are they related? • What is the difference between luminosity ...
Explosion of Sun - Scientific Research Publishing
... transparent “surface” of the photosphere, the photons escape as visible light. Each gamma ray in the Sun’s core is converted into several million visible light photons before escaping into space. Neutrinos are also released by the fusion reactions in the core, but unlike photons they very rarely int ...
... transparent “surface” of the photosphere, the photons escape as visible light. Each gamma ray in the Sun’s core is converted into several million visible light photons before escaping into space. Neutrinos are also released by the fusion reactions in the core, but unlike photons they very rarely int ...
Shortв•`lived radioactivity in the early solar system: The Superв•`AGB
... Al, 36Cl, and 41Cl (e.g., Goswami et al. 2001; Hsu et al. 2006; Duprat and Tatischeff 2007; Wasserburg et al. 2011a). Irradiation cannot make 60Fe, which can only be significantly produced via a chain of neutron-capture reactions and thus is a unique product of stellar nucleosynthesis. The true initi ...
... Al, 36Cl, and 41Cl (e.g., Goswami et al. 2001; Hsu et al. 2006; Duprat and Tatischeff 2007; Wasserburg et al. 2011a). Irradiation cannot make 60Fe, which can only be significantly produced via a chain of neutron-capture reactions and thus is a unique product of stellar nucleosynthesis. The true initi ...
The Origin, Structure, and Evolution of the Stars
... are very effective in scattering the light of distant stars acting like a smog to hinder our view ga and dust are a very low although the interstellar gas density medium the galaxy is so huge that the total mass of this material accounts for about one tenth the mass of the galaxy quite enough to pro ...
... are very effective in scattering the light of distant stars acting like a smog to hinder our view ga and dust are a very low although the interstellar gas density medium the galaxy is so huge that the total mass of this material accounts for about one tenth the mass of the galaxy quite enough to pro ...
Flow of Energy through the Star and Construction of Stellar Models
... molecular weight of the gas without ever providing a clear definition for the quantity. It is clearly time to do so, and we can do it easily given the ideal-gas law and our expression for the total number of particles N. Remember ...
... molecular weight of the gas without ever providing a clear definition for the quantity. It is clearly time to do so, and we can do it easily given the ideal-gas law and our expression for the total number of particles N. Remember ...
Chapter 13 Measuring the properties of stars
... Which of the following statements would explain the fact that larger molecules, such as amino acids, do not produce spectral lines in the OBAFGKM classification? A. Larger molecules require higher temperatures to show absorption lines. B. The spectra of hydrogen and helium are sufficient to classif ...
... Which of the following statements would explain the fact that larger molecules, such as amino acids, do not produce spectral lines in the OBAFGKM classification? A. Larger molecules require higher temperatures to show absorption lines. B. The spectra of hydrogen and helium are sufficient to classif ...
6.1 Introduction
... with a mass of 107 M ) is unique among Galactic globular clusters in showing two distinct populations of stars, a bluer population and a redder one, with quite distinct main sequences in the colour-magnitude diagram. The origin of these two populations is still unclear. This figure compares a small ...
... with a mass of 107 M ) is unique among Galactic globular clusters in showing two distinct populations of stars, a bluer population and a redder one, with quite distinct main sequences in the colour-magnitude diagram. The origin of these two populations is still unclear. This figure compares a small ...
WG4: Nuclear Astrophysics
... Cosmic gas is collected by gravitational attraction into higher density regions, to eventually form stars of different masses. These stars are stabilised against further gravitational concentration by the release of nuclear binding energy in their interiors. Depending on the total mass of the star d ...
... Cosmic gas is collected by gravitational attraction into higher density regions, to eventually form stars of different masses. These stars are stabilised against further gravitational concentration by the release of nuclear binding energy in their interiors. Depending on the total mass of the star d ...
Astronomy 112: The Physics of Stars Class 14 Notes: The Main
... that of the Sun. Of course this argument is a bit of a cheat: the way we got the homology argument in the first place is by assuming a particular scaling for the nuclear reaction rate with temperature ν, and, if the temperature gets too low, ν will change. Thus the limit is a bit more complicated. N ...
... that of the Sun. Of course this argument is a bit of a cheat: the way we got the homology argument in the first place is by assuming a particular scaling for the nuclear reaction rate with temperature ν, and, if the temperature gets too low, ν will change. Thus the limit is a bit more complicated. N ...
Stars
... by striking a balance between the gravity of their enormous mass and the pressure produced by the energy of fusion reactions. A main sequence star is in equilibrium as Hydrogen burning supports it against gravitational collapse. What happens as the hydrogen runs out? © 2007 Pearson Education Inc., p ...
... by striking a balance between the gravity of their enormous mass and the pressure produced by the energy of fusion reactions. A main sequence star is in equilibrium as Hydrogen burning supports it against gravitational collapse. What happens as the hydrogen runs out? © 2007 Pearson Education Inc., p ...
Cool as helium
... yellow spectral line signature from the Sun. Lockyer — the first editor of Nature — named it after the Greek word for the Sun, helios. It was the Scottish chemist Sir William Ramsay who first isolated helium in 1895, by treating the uranium mineral cleveite with mineral acids and removing nitrogen a ...
... yellow spectral line signature from the Sun. Lockyer — the first editor of Nature — named it after the Greek word for the Sun, helios. It was the Scottish chemist Sir William Ramsay who first isolated helium in 1895, by treating the uranium mineral cleveite with mineral acids and removing nitrogen a ...
AST1100 Lecture Notes
... will study the HR-diagram as a plot with surface temperature of stars on the x-axis and absolute magnitude on the other. In figure 3 you see a typical HR-diagram: Stars plotted according to their surface temperature (or color) and absolute magnitude. The y-axis shows both the luminosity and the abso ...
... will study the HR-diagram as a plot with surface temperature of stars on the x-axis and absolute magnitude on the other. In figure 3 you see a typical HR-diagram: Stars plotted according to their surface temperature (or color) and absolute magnitude. The y-axis shows both the luminosity and the abso ...
Stellar Remnants White Dwarfs Type Ia Supernovae Neutron Stars
... © 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley ...
... © 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley ...
ppt
... molecules just processed by the neutrinos? There aren’t as many of them as there are neutrinos, but their interaction cross sections are >>> than those of the neutrinos. If the end state of the supernova is a black hole, the collapse to the black hole might result before any of the photons could esc ...
... molecules just processed by the neutrinos? There aren’t as many of them as there are neutrinos, but their interaction cross sections are >>> than those of the neutrinos. If the end state of the supernova is a black hole, the collapse to the black hole might result before any of the photons could esc ...
Is the central binary system of the planetary nebula Henize 2
... several PNe that show a wide He II 5412 Å absorption line with a weak emission feature in the center of the wide absorption line. This forms a spectral structure similar to that of Henize 2–428. The most noticeable examples of this are the PNe He 2–105, He 2–434, and to some degree SP 3 and PC 12. ...
... several PNe that show a wide He II 5412 Å absorption line with a weak emission feature in the center of the wide absorption line. This forms a spectral structure similar to that of Henize 2–428. The most noticeable examples of this are the PNe He 2–105, He 2–434, and to some degree SP 3 and PC 12. ...
Interactive 4 - Hertzsprung-Russell Diagram Explorer
... b) Gamma rays are released in the core of red giant stars, in a set of nuclear fusion reactions known as the triple-alpha process. Two helium atoms fuse to create one beryllium atom and gamma radiation with energy of -0.0918 MeV. The beryllium atom then fuses with another helium atom to create a car ...
... b) Gamma rays are released in the core of red giant stars, in a set of nuclear fusion reactions known as the triple-alpha process. Two helium atoms fuse to create one beryllium atom and gamma radiation with energy of -0.0918 MeV. The beryllium atom then fuses with another helium atom to create a car ...
Spectral Classification of Stars
... Let χi be the ionization energy needed to remove an electron from an atom (or ion). For example, to convert neutral hydrogen (H I = H0) to ionized hydrogen (H II =H+) you can have χi = 13.6 eV for hydrogen in the ground state, or χi=3.40 eV for hydrogen in the first excited state, etc. Average must ...
... Let χi be the ionization energy needed to remove an electron from an atom (or ion). For example, to convert neutral hydrogen (H I = H0) to ionized hydrogen (H II =H+) you can have χi = 13.6 eV for hydrogen in the ground state, or χi=3.40 eV for hydrogen in the first excited state, etc. Average must ...
Type II supernova
A Type II supernova (plural: supernovae or supernovas) results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, and no more than 40–50 times, the mass of the Sun (M☉) for this type of explosion. It is distinguished from other types of supernovae by the presence of hydrogen in its spectrum. Type II supernovae are mainly observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies.Stars generate energy by the nuclear fusion of elements. Unlike the Sun, massive stars possess the mass needed to fuse elements that have an atomic mass greater than hydrogen and helium, albeit at increasingly higher temperatures and pressures, causing increasingly shorter stellar life spans. The degeneracy pressure of electrons and the energy generated by these fusion reactions are sufficient to counter the force of gravity and prevent the star from collapsing, maintaining stellar equilibrium. The star fuses increasingly higher mass elements, starting with hydrogen and then helium, progressing up through the periodic table until a core of iron and nickel is produced. Fusion of iron or nickel produces no net energy output, so no further fusion can take place, leaving the nickel-iron core inert. Due to the lack of energy output allowing outward pressure, equilibrium is broken.When the mass of the inert core exceeds the Chandrasekhar limit of about 1.4 M☉, electron degeneracy alone is no longer sufficient to counter gravity and maintain stellar equilibrium. A cataclysmic implosion takes place within seconds, in which the outer core reaches an inward velocity of up to 23% of the speed of light and the inner core reaches temperatures of up to 100 billion kelvin. Neutrons and neutrinos are formed via reversed beta-decay, releasing about 1046 joules (100 foes) in a ten-second burst. The collapse is halted by neutron degeneracy, causing the implosion to rebound and bounce outward. The energy of this expanding shock wave is sufficient to accelerate the surrounding stellar material to escape velocity, forming a supernova explosion, while the shock wave and extremely high temperature and pressure briefly allow for theproduction of elements heavier than iron. Depending on initial size of the star, the remnants of the core form a neutron star or a black hole. Because of the underlying mechanism, the resulting nova is also described as a core-collapse supernova.There exist several categories of Type II supernova explosions, which are categorized based on the resulting light curve—a graph of luminosity versus time—following the explosion. Type II-L supernovae show a steady (linear) decline of the light curve following the explosion, whereas Type II-P display a period of slower decline (a plateau) in their light curve followed by a normal decay. Type Ib and Ic supernovae are a type of core-collapse supernova for a massive star that has shed its outer envelope of hydrogen and (for Type Ic) helium. As a result, they appear to be lacking in these elements.