CAMBRIDGE, Mass., Sept. 2 (UPI) -- U.S. astronomers say they've discovered the first pair of supermassive black holes in a spiral galaxy similar to the Milky Way.
At about160 million light years from Earth the pair, discovered with NASA's Chandra X-ray Observatory, is the nearest known example of such a phenomenon, a NASA release said Wednesday.
The black holes, located near the center of the spiral galaxy NGC 3393, are likely the remnant of a merger of two galaxies of unequal mass a billion or more years ago, astronomers said.
Previous observations had indicated a single supermassive black hole existed in the center of NGC 3393, but Chandra's X-ray observations were able to discern two.
"If this galaxy wasn't so close, we'd have no chance of separating the two black holes the way we have," said Pepi Fabbiano of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
"Since this galaxy was right under our noses by cosmic standards, it makes us wonder how many of these black hole pairs we've been missing."