Pairs of stars that orbit around their common center of mass.
black body radiation
Radiation emitted by a hypothetical perfect radiator. The spectrum is continuous, and the wavelegth of maximum emission depends on the body's temperature.
black hole
A mass that has collapsed to such a small volume that its gravity prevents the escape of all radiation. Also, the volume of space from which radiation may not escape.
brown dwarf
A star whose omass is too low to ignite nuclear fusion. Heated by contraction.