Astronomers have witnessed a triplet of monster black holes swirling in the center of a distant galaxy, a new study says.
Astronomers have learned over the past decade or two that virtually every full-size galaxy such as our own Milky Way has a giant black hole lurking in its core. These monsters weigh in with a mass equal to millions or even billions of stars.
The new observations, however, described in the journal Nature, suggest that many galaxies have not one, but two or more giant black holes in their centers, orbiting each other in a tight gravitational dance that will ultimately lead the objects to merge together into something even more gigantic.
Watching these mergers will offer insight into how gravity behaves when stretched to its limits, astronomers predict, with clues revealed by monster black hole mash-ups such as the just-discovered triplet.
“We were quite surprised to find it,” says Roger Deane, of the University of Cape Town in South Africa, lead author of the report. In one sense, Deane and his colleagues shouldn’t have been surprised. It’s widely accepted that when galaxies come close together, their gravity can force them to form a single agglomeration of stars. In fact, the Milky Way and the (relatively) nearby Andromeda galaxy will probably experience such a merger in about four billion years. Since each galaxy hosts a single massive black hole, the resulting single galaxy should end up with two.
Deane and his group originally became interested in this particular galaxy, known by the unwieldy name SDSS J150243.091111557.3, because it had been flagged by the Sloan Digital Sky Survey (thus the “SDSS” in the name) as having what looked like two sources of bright light in its core.
That indicated the possibility of two black holes there, with the light coming not from the invisible objects themselves but from the whirlpools of gas heated to incandescence as they spiral in under the black holes’ intense gravity. Jets emitted by the black holes pinpointed their location.