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A steady "flickering" in the X-ray energy from a distant black hole suggests that it is about 10,000 times the mass of the Sun, making it one of the best known candidates for a new class of black holes.

The black hole is in the galaxy M74, which is 32 million light-years away. The orbiting Chandra X-ray Observatory discovered that the X-rays produced by a disk of hot gas around the black hole vary strongly over a period of about two hours. Using models that relate the period of such a variation to the mass of the black hole, a team of astronomers led by Jifeng Liu of the University of Michigan in Ann Arbor deduced that this one is 10,000 times the Sun's mass.

This would classify the object as an intermediate-mass black hole. Astronomers have discovered many good candidate black holes that are a few times as massive as the Sun, and many more in the hearts of galaxies that are a few million to a few billion times as massive as the Sun. But the intermediate variety has proved elusive. The M74 black hole is one of the best candidates. Such black holes could form from the mergers of smaller black holes in a star cluster, or they could be from the cores of small galaxies that were swallowed by larger ones.