Search results
Results From The WOW.Com Content Network
In astrophysics, stellar nucleosynthesis is the creation of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. As a predictive theory, it yields accurate estimates of the observed abundances of the elements.
Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.
In astrophysics, silicon burning is a very brief [1] sequence of nuclear fusion reactions that occur in massive stars with a minimum of about 8–11 solar masses. Silicon burning is the final stage of fusion for massive stars that have run out of the fuels that power them for their long lives in the main sequence on the Hertzsprung–Russell diagram.
Stars fuse light elements to heavier ones in their cores, giving off energy in the process known as stellar nucleosynthesis. Nuclear fusion reactions create many of the lighter elements, up to and including iron and nickel in the most massive stars. Products of stellar nucleosynthesis remain trapped in stellar cores and remnants except if ...
Any stars in the universe can collide, whether they are "alive", meaning fusion is still active in the star, or "dead", with fusion no longer taking place. White dwarf stars, neutron stars , black holes , main sequence stars , giant stars , and supergiants are very different in type, mass, temperature, and radius, and accordingly produce ...
A stellar core is the extremely hot, dense region at the center of a star. For an ordinary main sequence star, the core region is the volume where the temperature and pressure conditions allow for energy production through thermonuclear fusion of hydrogen into helium .
The star "enters" the main sequence when its core reaches a temperature (several million kelvins) high enough to begin fusing hydrogen-1 (the predominant isotope), and establishes hydrostatic equilibrium. (In astrophysics, stellar fusion is often referred to as "burning", with hydrogen fusion sometimes termed "hydrogen burning".) Over its main ...
For lower mass stars on the red-giant branch, the helium accumulating in the core is prevented from further collapse only by electron degeneracy pressure. The entire degenerate core is at the same temperature and pressure, so when its density becomes high enough, fusion via the triple-alpha process rate starts throughout the core.