Chapter 12 Flashcards
(16 cards)
Core hydrogen burning
The energy-burning stage for main-sequence stars, in which the helium is produced by hydrogen fusion in the central region of the star. A typical star spends up to 90 percent of its lifetime in hydrostatic equilibrium brought about by the balance between gravity and the energy generated by core hydrogen burning.
Hydrogen shell-burning
Fusion of hydrogen in a shell that is driven by contraction and heating of the helium core. Once hydrogen is depleted in the core of a star, hydrogen burning stops and the core contracts due to gravity, causing the temperature to rise, heating the surrounding layers of hydrogen in the star, and increasing the burning rate there.
Subgiant branch
The section of the evolutionary track of a star that corresponds to changes that occur just after hydrogen is depleted in the core, and core hydrogen is depleted in the core, and core hydrogen burning ceases. Shell hydrogen burning heats the outer layers of the star, which causes a general expansion of the stellar envelope.
Red giant branch
The section of the evolutionary track of a star corresponding to intense hydrogen shell burning, which drives a steady expansion and cooling of the outer envelope of the star. As the star gets larger radius and its surface temperature cools, it becomes a red giant.
Helium flash
An explosive event in the post main-sequence evolution of a low-mass star. When helium fusion begins in a dense in a dense stellar core, the burning explosive in nature. It contains until the energy released is enough to expand the core, at which point the star achieves stable equilibrium again.
Horizontal branch
Region of the Hertzsprung-Russel diagram where post-main-sequence stars again reach hydrostatic equilibrium. At this point, the star is burning helium in its core and fusing hydrogen in a shell surrounding the core.
Planetary nebula
The ejected envelope of a red-giant star, spread over a volume roughly the size of our solar system.
Black dwarf
The endpoint of the evolution of an isolated low-mass star. After the white dwarf stage, the star cools to the point where it is a dark “clinker” in interstellar space.
Nova
A star that suddenly increases in brightness often by a factor of as much as 10,000, then slowly fades back to its original luminosity. A nova is the result of an exposition on the surface of a white-dwarf star, caused by matter falling onto its surface from the atmosphere of a binary companion.
Accretion disk
Flat disk of matter spiraling down onto the surface of a neutron star or black hole. Often, the matter originated on the surface of a companion star in a binary star system.
Red supergiant
An extremely luminous red star. Often found on the asymptotic giant branch of the Hertzsprung-Russel diagram.
Core-collapse supernova
See Type II supernovae
Type I supernovae
One possible explosive death of a star. A white dwarf in a binary star system can accrete enough mass that it cannot support its own weight. The star collapses and temperatures become high enough for carbon fusion to occur. Fusion begins throughout the white dwarf almost simultaneously, and an explosion results.
Type II supernovae
One possible explosive death of a star, in which the highly evolved stellar core rapidly implodes and then explodes, destroying the surrounding star. U
Carbon-detonatiom supernova
See Type I supernova.
Supernova remnants
The scattered glowing remains from a supernova that occurred in the past . The Crab Nebula is one of the best-studied supernova remnants.
