Monday, February 13, 2006

See a nova!

If you are up nice and early in the morning, why not try and find a nova with your naked eye? All you need is a dark sky, a view of the east, a lot of patience, and some star maps. An article on the nova can be found at Sky and Telescope.

A "nova" is a thermonuclear explosion on the surface of a white dwarf. "Huh?" you say? Okay. Let's back up a bit.

White dwarfs are the "ashes" of a dead star. A star burns all of its fuel, changing it from hydrogen into helium and then on into carbon and oxygen. All that is left is a glowing ember abouth the size of the Earth.

Many stars have companion stars. If the two stars are close enough, the gravity of the white dwarf can pull some gas from the surface of the companion star onto its own surface. After enough gas has built up, it gets hot enough to start fusion, and BOOM! Just like a hydrogen bomb, the gas rapidly ignites, fuses into helium, and creates an explosion.

While these explosions are big, they are MUCH smaller than supernovae, in which an entire star is ripped apart by a powerful explosion. In novae, the white dwarf survives. After the explosion settles down, it begins to steal more gas from the neighboring star, and the cycle starts again.

The currently-visible nova (with the exciting name RS Ophiuchui), last was visible in 1985, and before that in 1967.

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