Astrophysics (index)

White Dwarf

(degenerate dwarf)
(stellar remnant of mostly electron-degenerate matter)

A White Dwarf is a star past its main sequence thermonuclear stage that has expelled its exterior and only the core remains. Electron Degeneracy prevents their further collapse into Neutron Stars. For being the remains of a star, it is classified as a Stellar Remnant.

They generally transfer their energy to the surface by Conduction (interaction of particles) rather than Radiative Transfer (RT).

Most are Oxygen (O) and Carbon (C) but under some conditions can have neon, magnesium, or Helium (He). White dwarfs are no more than 1.4 solar masses (the Chandrasekhar Limit) and if they grow beyond that, e.g., due to mass transfer from a companion, a type Type Ia Supernova results. White dwarfs begin at the Temperature left over form the main sequence, then cool very slowly. When sufficiently cooled and no longer emitting appreciable Electromagnetic Radiation (EMR), the term Black Dwarf is used.

Types:

  • Carbon-Oxygen White Dwarf - typical
  • Oxygen-Neon-Magnesium White Dwarf - progenitor was between 8 and 10.5 solar masses
  • Helium White Dwarf - created from binaries

Some white dwarf spectral types (e.g., "DBV"):

DAJust H Spectral Lines
DBJust He I lines
DCNo lines
DOIncludes H II lines
DZMetal lines
DQCarbon lines
DXUnclear

Optional letter designating other features:

PPolarized
HMagnetism but no Polarization
EEmission Lines
VVariable

(star type,degeneracy)
http://en.wikipedia.org/wiki/White_dwarf

Referenced by:
Black Widow Pulsar (B1957+20)
Calcium-Rich Gap Transient
Chandrasekhar Limit
Compact Object
Cataclysmic Variable Star (CV)
Dwarf Nova
Electron Degeneracy
Giant Star
H-R Diagram (HRD)
Low Mass Star
Neutron Star
Nova
Procyon
Red Giant
Supernova (SN)
Stellar Remnant
Stellar Rotation
Sun
Tolman-Oppenheimer-Volkoff Limit (TOV)
Type Ia Supernova
Variable Star

index