Nebula
This article refers to nebulas in space. For the band Nebula, go to Nebula (band).
A nebula (Latin for "mist"; plur. nebulae) is an interstellar cloud of dust and gas. Originally nebula was a catch-all name for any extended astronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive).
Nebulae are classified by how they are illuminated:
- Diffuse nebula are illuminated nebula
- Dark nebulae are unilluminated. They can be detected when they obscure stars or other nebulae.
Nebulae are the birthplace of stars. The dust of the nebula contracts under its own gravitational pull to form new stars. The newly-formed stars can ionize the surrounding gas to produce an emission nebula.
Some nebulae are created by stellar explosions. A star that undergoes the transition to a white dwarf blows off its outer layer to form a planetary nebula. Novas and supernovas can also create nebulae known as nova remnants and supernova remnants respectively.
See also:
The Nebula Awards, annually given out by the Science Fiction and Fantasy Writers of America, are named after nebulae.
