Knowra White dwarf White dwarf A compact stellar remnant supported against gravitational collapse by electron degeneracy pressure. Most form when low- or intermediate-mass stars shed their outer layers after exhausting nuclear fuel.
Electron degeneracy pressure : Pressure arising from the Pauli exclusion principle, which prevents electrons from occupying identical quantum states. It supports a white dwarf against gravity even after nuclear fusion ends.
Asymptotic giant branch : A late evolutionary phase of low- and intermediate-mass stars with an inert core and a luminous, unstable envelope. Its mass loss helps expose the stellar core that becomes a white dwarf.
Pauli exclusion principle : The quantum rule that identical fermions cannot occupy the same quantum state simultaneously. It underlies the electron degeneracy pressure that supports white dwarfs.
White dwarf luminosity function : The distribution of white dwarfs by luminosity in a population or region of space. Its faint-end cutoff can estimate the age of an old stellar population.
Neutron star : A compact stellar remnant supported primarily by neutron degeneracy and nuclear forces. It is generally denser than a white dwarf and forms from more massive stellar progenitors.
Chandrasekhar limit : The maximum mass, about 1.4 solar masses, of a cold, nonrotating white dwarf supported by electron degeneracy pressure. Above this limit, electron pressure cannot support the star against collapse.
Planetary nebula : An expanding shell of ionized gas ejected by a dying low- or intermediate-mass star. The nebula often surrounds the newly exposed hot core on its way to becoming a white dwarf.
Fermion : A particle with half-integer spin that obeys the Pauli exclusion principle. Electrons are fermions, so their quantum statistics provide the remnant's pressure support.
White dwarf cosmochronology : The use of white dwarf cooling ages to estimate the ages of stellar populations. Cooling rates turn these remnants into clocks for ancient star clusters and the Galactic disk.
Black hole : A region of spacetime whose gravity prevents anything, including light, from escaping beyond its event horizon. Unlike a white dwarf, it has no stable surface supported by electron degeneracy pressure.
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