Difference between a nova, supernova and hypernova

NOVA: A white dwarf star pulls matter off of a companion red giant star until a powerful nuclear fusion explosion occurs on the dwarf’s surface. The star is not destroyed and additional explosions can occur, a phenomenon called a recurrent nova.

SUPERNOVA: Much more brilliant than a nova, a supernova can shine brighter than an entire galaxy for a brief time.

Astronomers identify two major types of supernovas:

Type I Supernova: A white dwarf star pulls matter from a companion star until the dwarf’s dead core re-ignites in a thermonuclear explosion that destroys the star. This is similar to a nova but the explosion is much more powerful. A Type I supernova has no hydrogen in its spectrum.

Type II Supernova: A star several times more massive than the sun runs out of nuclear fuel and collapses under its own gravity until it explodes. A Type II supernova has hydrogen in its spectrum.

SUPERLUMINOUS SUPERNOVA (Hypernova): A burst 5 to 50 times more energetic than a supernova. A hypernova may or may not be associated with a powerful burst of gamma radiation.

Novas are relatively small explosions in double star systems. They come about when a white dwarf’s intense gravity tugs material away from a companion star. Gas piles up around the white dwarf and eventually becomes dense enough to ignite in a burst of nuclear fusion.

Most supernovas, meanwhile, mark the deaths of massive stars and the formation of neutron stars. They are triggered when a shockwave tears through the outer layers of a dying star, igniting a firestorm of nuclear fusion.

Finally, hypernovas are ultra-energetic supernovas marking the birth of black holes and associated with the release of intense gamma-ray bursts.

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