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Nova Cygni 1975

August 29, 2010

Cygnus, the swan, glides high across the sky tonight. It's high in the east at nightfall, with its brightest star, Deneb, marking its tail.

35 years ago tonight, the swan's tail grew even more impressive. That's because a star not far from Deneb in our sky staged a powerful eruption. It briefly grew more than two million times brighter than before -- bright enough to rival Deneb.

It's known as Nova Cygni 1975. It was the result of an act of stellar thievery that had been going on for millennia.

The eruption took place in a binary system -- two stars locked in a mutual orbit. One star is a white dwarf -- the small, dense corpse of a star that was once like the Sun. The other is a red dwarf -- a faint stellar ember.

The white dwarf's gravity pulled gas from its companion. An extremely powerful magnetic field funneled the gas onto the white dwarf's poles. From there, it spread out to form a superhot "skin" around the white dwarf. When it got hot enough, it triggered an explosion that blasted the gas into space. For a while, the nova shone almost as bright as Deneb. Within about a week, though, it had faded from sight.

The blast was so strong that it changed the white dwarf's rotation speed. Before the blast, the system was synchronized so that the same side of one star always faced the same side of the other star, just as the same side of the Moon always faces Earth. But the explosion threw them out of sync -- by about four minutes.

Script by Damond Benningfield, Copyright 2010

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