TUCSON, Ariz. -- Sixty years after a theorist first suggested that the universe might be sprinkled with bizarre objects that came to be known as black holes, astronomers have found the first evidence for one that is so compelling "a jury would convict," one said yesterday.
The suspect appears to be a supermassive black hole -- as weighty as 36 million suns -- in the center of a galaxy called NGC 4258, about 21 million light years from Earth.
While most astronomers have long believed such dense concentrations of matter do exist -- objects so heavy that their gravitational pull prevents anything, even light itself, from escaping their grasp -- it has never been proven.
The find is being reported today in the journal Nature.
The discovery was made with a collection of radiotelescopes that spans almost half the globe, electronically linked to work like a single gigantic satellite dish to pick up radio waves. Called the Very Long Baseline Array, it was operated by a team headed by James Moran of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
Dr. Moran said the linked radiotelescopes can observe details so small that, "if you had an astronaut on the moon, you could watch his fingernails grow" from Earth. Its ability to detect fine details is 1,000 times greater than the Hubble's.
The density of matter it found -- the key measurement for determining whether the object is a black hole -- is about 40,000 times greater than was reported last year for a different galaxy called M87, observed by the Hubble Space Telescope. At the time, it was the best evidence for a supermassive black hole.
Dr. Moran conceded the concentration could be something else, such as a cluster of heavy stars but said such stars would probably collapse into each other and form a black hole anyway.