Star Lifecyle Flashcards
What is the first part of a star’s life?
Protostar, formed from clouds of gas and dust (remnants of supernovae) which become dense clumps due to contraction under gravity
What occurs after the protostar?
Nova, temperature at centre of clumps reaches a few million degrees and hydrogen fuses causing luminosity to increase
Explain what occurs in a main sequence star?
Core hydrogen burning, fusion of hydrogen provides enough radiation pressure to prevent gravitational collapse
What occurs when core hydrogen burning stops?
Shell hydrogen burning, helium builds up in core and gravity causes core contraction, core heats up raising temperature of surrounding hydrogen enough to fuse
What occurs after shell hydrogen burning?
Core helium burning (red giant), core continues to collapse until core hot and dense enough for helium to fuse into carbon and oxygen, radiation pressure pushes out layers of star outwards which cool
What occurs after core helium burning in a red giant?
Shell helium burning, helium runs out forming a carbon-oxygen core which contracts
What occurs after shell helium burning for stars of <1.4 solar masses?
Helium shell unstable as core collapses causing star to pulsate and eject outer layers leaving a hot dense solid core (white dwarf) which eventually cores into a black dwarf
What occurs after shell helium burning for stars of >1.4 solar masses?
Red supergiant, core to shell burning goes beyond helium fusion up to iron, radiation pressure rapidly decreases causing core collapse, outer layers spread (supernova)
What occurs in stars after a supernova which are >1.4 solar masses?
Further collapse of core stopped by strong force interactions between neutrons, form a neutron star
What occurs in stars after a supernova which are >3.4 solar masses?
Pass neutron degeneracy pressure, meaning further core collapse into a black hole
