Cosmology And Astrophysics Flashcards
How are protostars formed?
Gravity causes a nebulae to spin inwards and form a dense center. GPE is converted to KE and hot, dense dust and gas is left (protostar)
How are main sequence stars formed
from protostars?
Temperature and pressure must be high enough for hydrogen gas in the protostar to overcome the electrostatic forces of repulsion and undergo nuclear fusion (hydrogen to helium). When fusion begins main sequence star is formed. outward pressure from fusion = gravity.
How is a red giant formed from a low mass main sequence?
Low mass = 0.5M-10M. Smaller,cooler core and remain in main sequence for longer. When hydrogen supplies are low, gravitational force> gas pressure. This causes the core to collapse inwards and the outer layers to expand and cool. New hot core begins to fuse helium into heavier elements up to carbon.
Evolution of a red giant to a white dwarf?
Star runs out of fuel, outer layers expand, creating a planetary nebulae. The remaining core contracts becoming a white dwarf- temp around 3000K and no fusion. Electron degeneracy pressure (two electrons can’t be in the same place) stops the core from collapsing. As long as the mass is below 1.44M (Chandrasekhar limit) the white star is stable.
