Kelly Anderson, age 12, of Moab, Utah, for her question:
What exactly is a supernova?
A supernova is a superior nova and when astronomers refer to more than one of each, they call them supernovae and novae. These endings are Latin plurals. However, the Big Dictionary says that we ordinary folk may refer to numbers of these razzle dazzle stars as novas and supernovas. Actually the novas are very rare events and a stupendous supernova appears only once in several centuries.
The word "nova" means a new star and it was coined ages ago when early astronomers thought that a bright new star had appeared in the heavens. We now know that a nova is actually a fairly ordinary star that suddenly explodes like a celestial firecracker. The blazing gases in its outer shell shoot out at fantastic speeds and continue to expand through space. Suddenly the dim, distant object becomes 10,000 or perhaps 100,000 times brighter. For a time, the brilliant nova may outshine all the other visible stars in our sky.
One would think that such a dazzling display would shatter the star beyond repair. But astronomers suspect that it loses only about a hundred thousandth part of its total gaseous material. Several stars have been known to survive and become novas again and again. But so far as we know, a star can become a super duper supernova only once.
When a starry supernova explodes, it may become a billion times brighter in just a few days. Phase one happens suddenly, as shells of gases explode outward almost as fast as the speed of light. In a few days, the supernova may become as bright as a 100 billion suns brighter than the total stars in our Galaxy.
This dazzling Phase One may last weeks or months. But when it subsides, the erupted gases continue to stream out through vast regions of space for many centuries. Astronomers suspect that a star that becomes a supernova loses as much as ten per cent of its gaseous material. During the past 2,000 years only about 14 supernovas have occurred in our entire Galaxy, most of them beyond our range of vision.
In 1054 A.D., Chinese astronomers reported a dazzling new star in the constellation Taurus, the Bull. Modern telescopes reveal the great halo of its glowing, gaseous debris which astronomers estimate still is expanding at some 70 million miles a day. We call it the Crab Nebula.
Someday, no doubt, we shall know exactly what causes a supernova and also what happens to the original star after the catastrophe. Some astronomers suspect extra massive stars tend to explode. After the dazzling explosion, the remaining material seems to collapse into a tiny, high energy star called a pulsar.
Several pulsars have been detected within the debris of old supernovas. The remains of such a star appear to be crushed into a tight little ball with a core perhaps five miles wide. It is made of densely packed neutrons that weigh hundreds of thousands of tons per thimbleful. For 1,000 years, a fast spinning pulsar may emit more energy than 1,000 suns and gradually subside through perhaps 100,000 years.