–1– Order of Magnitude Astrophysics
... When the stars are plotted in a log T s – log L plane we thus expect them to lie within a line with slope (1/12) ≈ 0.08. The observed slope is ∼ 0.13. We saw above that stars are gravitationally bound systems in which self-sustaining nuclear reactions are taking place in the center. The process of c ...
... When the stars are plotted in a log T s – log L plane we thus expect them to lie within a line with slope (1/12) ≈ 0.08. The observed slope is ∼ 0.13. We saw above that stars are gravitationally bound systems in which self-sustaining nuclear reactions are taking place in the center. The process of c ...
The Lives of Stars From Birth Through Middle Age (Chapter 9)
... 2. A proton and a deuterium atom combine to form a helium-3 atom (two protons with one neutron) and a gamma ray. 3. Two helium-3 atoms combine to form a helium-4 atom (two protons and two neutrons) and two protons. These reactions account for 85 percent of the sun's energy. The remaining 15 percent ...
... 2. A proton and a deuterium atom combine to form a helium-3 atom (two protons with one neutron) and a gamma ray. 3. Two helium-3 atoms combine to form a helium-4 atom (two protons and two neutrons) and two protons. These reactions account for 85 percent of the sun's energy. The remaining 15 percent ...
Vocabulary Review
... a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons ...
... a star that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons ...
Homework, August 29, 2002 AST110-6
... 1. If nuclear fusion of hydrogen in the core of the Sun were to stop now, what would we see on the surface of the Sun tomorrow? Why? Will we be able to tell that hydrogen burning in the core has stopped? How? (20pt) (Hint: What particles that are generated by the fusion of hydrogen can escape from t ...
... 1. If nuclear fusion of hydrogen in the core of the Sun were to stop now, what would we see on the surface of the Sun tomorrow? Why? Will we be able to tell that hydrogen burning in the core has stopped? How? (20pt) (Hint: What particles that are generated by the fusion of hydrogen can escape from t ...
Comparing Earth, Sun and Jupiter
... due to the fusion of hydrogen into helium in the core This is the only process that can produce sufficient energy Classically fusion would not be efficient enough: requires quantum mechanics (barrier tunneling). Energy is transported to the surface via either radiation or convection. The Sun ...
... due to the fusion of hydrogen into helium in the core This is the only process that can produce sufficient energy Classically fusion would not be efficient enough: requires quantum mechanics (barrier tunneling). Energy is transported to the surface via either radiation or convection. The Sun ...
Chapter 27 Stars and Galaxies
... Some white dwarfs do not just cool and die. They will have one or more large explosions and become a nova A supernova is a star that has such a tremendous explosion that it blows itself apart. Before a supernova all of the stars elements will be fused into iron ...
... Some white dwarfs do not just cool and die. They will have one or more large explosions and become a nova A supernova is a star that has such a tremendous explosion that it blows itself apart. Before a supernova all of the stars elements will be fused into iron ...
The genesis and characteristics of black holes
... if heat is transported off collapse free falling time: protostar is born ...
... if heat is transported off collapse free falling time: protostar is born ...
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.