Physics of white dwarfs
Electron Degeneracy and the
Pauli Exclusion Principle
The Pauli exclusion
principle is defined by Dr. Steven S. Zumdahl,
"In a given atom no two electrons can have the same set of four quantum
numbers." Due to this principle, only two
electrons can inhabit a single energy level. The electrons that
share the same energy level have opposite intrinsic angular momentums
which is more commonly known as "spin". To determine the
direction of the spin the angular momentum vector is analyzed.
a degenerate gas where the electrons exist in the lowest allowed energy
level. Degeneracy pressure is caused by a degenerate gas. A
degenerate gas is different from an ordinary gas because their
electrons have much greater energies and higher momentums. The
higher energy and momentum is the cause of the increase in
pressure. The increase in pressure results in the electrons being
in a higher state than what would be predicted.
A white dwarf uses electron
degeneracy pressure to support itself. It is because of the
electron degeneracy pressure that white dwarfs have a small size
relative to other types of stars. The star is in the process of
collapsing until it reaches a point or equilibrium with the electron
degeneracy pressure.
Degenerate gases are excellent heat conductors. White Dwarfs are
99% degenerate gas and that percent of the star has a temperature of
around 10,000,000 K. In the remaining 1% exists on the outer most
part of the star and is only 10,000 K.
Another important physical characteristic is the very strong magnetic
field. Zeeman splitting measurements report that the magnetic
field may be as strong as 10,000,000 gauss.
When searching the cosmos white
dwarfs are difficult to
pinpoint. They are found by their gravitational influence in
binary systems. When a white dwarf is a part of a binary system
the other star's orbit is noticeably altered.