In the past few decades, it has become part of astronomical lore, if not quite a law, that at the center of every luminous city of light, called a galaxy, lurks something like a hungry Beelzebub, a giant black hole into which the equivalent of millions or even billions of suns have disappeared. The bigger the galaxy, the more massive the black hole at its center.
So it was a surprise a decade ago when Marc Postman, of the Space Telescope Science Institute, using the Hubble Space Telescope to survey clusters of galaxies, found a supergiant galaxy with no sign of a black hole in its center. Normally, the galaxy’s core would have a kink of extra light in its center, a kind of sparkling cloak, produced by stars that had been gathered there by the gravity of a giant black hole.
On the contrary, at the exact center of the galaxy’s wide core, where a slight bump in starlight should have been, there was a slight dip. Moreover, the entire core, a cloud of stars some 20,000 light years across, was not even centered on the exact middle of the galaxy.
“Oh, my God, this is really unusual,” Tod Lauer, an expert on galactic nuclei at the National Optical-Infrared Astronomy Research Laboratory in Tucson, Ariz., and an author on the paper, recalled saying when Dr. Postman showed him the finding.
That was in 2012. In the years since, the two researchers and their colleagues have been ransacking the galaxy, looking for X-rays or radio waves from the missing black hole.
The galaxy is the brightest one in a cluster known as Abell 2261. It is about 2.7 billion light-years from here, in the constellation Hercules in the northern sky, not far from the prominent star Vega. Using the standard rule of thumb, the black hole missing from the center of the 2261 galaxy should be 10 billion solar masses or more, comparable to the mightiest of these monsters known to astronomers. The black hole at the center of the Milky Way galaxy is only about four million solar masses.
So where has nature stashed the equivalent of 10 billion suns?
One possibility is that the black hole is there but has gone silent, having temporarily run out of anything to eat. But another provocative possibility, Dr. Lauer and his colleagues say, is that the black hole was thrown out of the galaxy altogether.
Missing: One Black Hole With 10 Billion Solar Masses (Published 2021)
One of the biggest galaxies in the universe seems to lack its dark centerpiece.
