Question

Choose the correct statements from the following list referring to white dwarfs. (Give ALL correct answers, i.e., B, AC, BCD...)

A) White dwarfs are less dense than red giants.

B) White dwarfs cool slowly because they are small and eventually fade-out to become black dwarfs.

C) The pressure that balances gravity in a white dwarf is called degenerate electron pressure.

D) Stars with a mass like the Sun will end up as a white dwarf star.

E) White dwarfs with mass greater than 1.4 times the Sun's mass cannot exist.

F) The power source of white dwarfs is left-over heat. G) White dwarfs are the coolest main sequence stars.

Answer 1

BCDEF

A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter.
The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy. As a result, it cannot support itself by the heat generated by fusion against gravitational collapse, but is supported only by electron degeneracy pressure, causing it to be extremely dense. The physics of degeneracy yields a maximum mass for a non-rotating white dwarf, the Chandrasekhar limit—approximately 1.44 times M0(mass of the sun)—beyond which it cannot be supported by electron degeneracy pressure.A white dwarf is very hot when it forms, but because it has no source of energy, it will gradually cool as it radiates its energy. This means that its radiation, which initially has a high color temperature, will lessen and redden with time. Over a very long time, a white dwarf will cool and its material will begin to crystallize, starting with the core. The star's low temperature means it will no longer emit significant heat or light, and it will become a cold black dwarf.
White dwarfs are composed of one of the densest forms of matter known, surpassed only by other compact stars such as neutron stars.