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Too Close

September 20, 2011

Any wise space traveler knows not to get too close to a black hole. After all, a black hole is a dead star with such powerful gravity that nothing — not even light, the fastest thing in the universe — can escape it.

A year ago, astronomers discovered a source of X-rays in the constellation Ophiuchus. The X-rays were coming from material that was plunging into a previously unknown black hole. Gravity and friction heat the material to such high temperatures that it emits X-rays before falling into the black hole.

By monitoring the X-rays, astronomers made a further discovery: A small red star, known as a red dwarf, orbits the black hole. The red dwarf is so close to the black hole that it’s losing gas to its dark partner. And of all the stars known to be orbiting black holes, this one has the shortest orbital period — it circles the black hole once every two hours and 25 minutes.

That means the red dwarf must be dangerously close to the black hole. After all, in our solar system, the planets with the shortest orbital periods are the ones closest to the Sun. But even Mercury — the Sun’s closest planet — takes a full 88 days to make one revolution.

The fast orbit means the red dwarf probably lies less than a million miles from the black hole. At such close range it will continue to lose more and more mass to its ravenous partner — and eventually, the black hole may consume the entire star.


Script by Ken Croswell, Copyright 2011


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