The Last Day, Part III
Taurus, the bull, is one of the highlights of the early morning sky this month. It clears the horizon by around 2 or 3 a.m. Near the tip of one of its horns is one of the most famous objects in the sky: the Crab Nebula. It's the wispy remnant of a supernova - a star that exploded almost a thousand years ago.
If you see pictures of the Crab, you'll notice that it's spread out, with dense filaments stretching in various directions.
The shape of the nebula is telling us something about how supernovae explode. They don't expand evenly in all directions. Instead, much of their material seems to blast out along powerful "jets" that are directed from the star's poles.
Astronomers are still working out how that works. They know that a supernova can be produced by the explosion of a big, heavy star. The star's core collapses to form a neutron star or black hole, and its outer layers blast into space. As the core collapses, it emits a torrent of particles that help push the outer layers away.
But University of Texas astronomers suspect that something else is contributing to the explosion. As the star's core collapses, it spins much faster, producing a powerful magnetic field. This field may help drive the explosion.
The astronomers are using both mathematical models and observations of real supernovae. The combination may help them understand why these powerful blasts look so stretched out.
Script by Damond Benningfield, Copyright 2005
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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