Dictionary

When stars with up to ten solar masses have exhausted the fuel of light atomic nuclei they need to sustain nuclear fusion reactions, they collaps to form a White Dwarf: a comparatively small ball of gas, prevented from further collapse by a quantum mechanical phenomenon, the so-called degeneracy pressure of its electrons.

One way of determining the masses of White Dwarfs uses an effect of general relativity, namely the gravitational redshift – more information about this can be found in the spotlight text Gravitational redshift and White Dwarf stars.