Regal Explosions

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A little star can pack a wallop -- even after it's dead.

Consider a star that suddenly appeared in the constellation Cassiopeia, the queen, more than four centuries ago. It's known as Tycho's supernova for Danish astronomer Tycho Brahe, who observed and wrote about it.

At the time, neither Tycho nor anyone else had any clue why the star had suddenly flared up. But today, we know that it was an explosion -- one of the most powerful blasts in the universe.

In fact, it was a big punch from a little star: a white dwarf -- the small, dense corpse of a star that was once like the Sun.

The star didn't blow up on its own, though. Instead, it had help from a companion. The two stars circled each other in a tight orbit. The gravity of the white dwarf pulled hot gas from the surface of the companion. When enough gas piled up on the white dwarf, it triggered a runaway thermonuclear explosion, blasting the star to bits.

Thousands of years later -- in early November of 1572 -- the light from that explosion reached Earth. For a while, the star was bright enough to see in daylight.

Observations by Tycho and others showed that the star was well beyond the Moon -- in a realm that was supposed to be perfect and unchanging. The star helped trigger a scientific revolution -- one that changed human understanding of the universe and our place in it -- quite a wallop from a little star.

We'll talk about another supernova in Cassiopeia tomorrow.

Script by Damond Benningfield, Copyright 2009

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