In the constellation Ursa Major
Approximately 1,000 times the mass of the Sun
Diameter equal to the size of Mars
Something near the core of the galaxy M82 is pumping out copious amounts of X-rays. But the source, cataloged as M82 X-1, isn't steady. One possible explanation is a black hole perhaps 1,000 times as massive as the Sun.
The X-ray source is in or near a cluster of hot, young stars about 600 light-years from the core of M82, which is classified as a starburst galaxy. The galaxy is giving birth to tens of thousands of stars, versus only a handful in the Milky Way.
Using space-based X-ray telescopes, astronomers have seen the source of X-rays grow periodically stronger and fainter. The type of X-rays, and the way they rise and fall, are similar to the X-rays produced by accretion disks around black holes in the Milky Way that are a few times the mass of the Sun.
But the rise and fall of the X-rays in M82 X-1 takes longer than those of the known black holes in the Milky Way. That suggests that the source of the X-rays is larger; it takes more time for light (and other forms of electromagnetic energy, including X-rays) to cross a larger object than a smaller one, so any "flickering" is slower.
From the length of the variations, and the distance to M82, astronomers calculate that the most likely source for the X-rays is a black hole that is roughly 1,000 times as massive as the Sun. The black hole is pulling in gas from a large, heavy companion star. As the gas approaches the black hole it's heated to millions of degrees, so it emits X-rays.
If the black hole is confirmed, M82 X-1 would become one of just a handful of known intermediate-mass black holes.
Follow-up observations by a sensitive network of radio telescopes, however, detected no radio waves from M82 X-1, suggesting that if the source is a black hole, it must be less massive than indicated by the X-ray observations.
So while there is a strong case for the intermediate-mass black hole, it's not a conclusive one. More observations are needed to confirm the source of the X-rays from M82 X-1.
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This document was last modified: March 14, 2012.