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The Question

(Submitted February 02, 1998)

What is a Nova? Can you please simplify this for me since I'm new to astronomy? What is the relationship between a Nova and a Supernova?

The Answer

A nova is a sudden brightening of a star. Novae are thought to occur on the surface of a white dwarf star in a binary system with another star. If these two stars are close enough to each other, material from one star can be pulled off its surface and onto the white dwarf. Occasionally, the temperature of this new material on the surface of the white dwarf may become hot enough to start nuclear fusion and suddenly the surface of the white dwarf will start to fuse the hydrogen into helium over its surface. This causes the white dwarf to suddenly become very bright. Ancient astronomers, who did not have telescopes and other instruments modern astronomers now have, did not realize that there was a star already there, and so they would just see a new star where they had not seen one before. "Stella Nova" means "new star" in Latin and this is where novae got their name. Supernovae were once thought to just be really bright novae (hence the addition of "super" to their name). If you look at

you can see there are two types of supernova, one of which occurs in the same binary systems as nova. If a nova fails to clear enough material off the surface of the white dwarf, enough may collect for the entire star to be destroyed by a very large (a "super") nova explosion. The other type of supernova is from the end of a massive isolated star and is not related to nova at all.

Jesse Allen
for Ask an Astrophysicist

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