Astronomers working at the National Radio Astronomy Observatory (NRAO) in New Mexico have discovered a mysterious object in the Cygnus A galaxy. Cygnus A is about 800 million light-years from Earth and is one of the strongest sources of radio waves in the known universe.
The object was first spotted by the Hubble Space Telescope in 1994, but it was believed to be a cluster of young stars at the time. These most recent observations show that the object has very quickly become “extraordinarily bright,” baffling astronomers as to what its identity might be.
Rick Perley, an NRAO astronomer who spotted the luminous anomaly, says that whatever the object is, it lit up to its current brightness relatively recently:
To our surprise, we found a prominent new feature near the galaxy's nucleus that did not appear in any previous published images. This new feature is bright enough that we definitely would have seen it in the earlier images if nothing had changed. That means it must have turned on sometime between 1996 and now.
There are two leading theories about what the ‘extraordinarily bright’ object might be: one, that it could be a black hole outburst. An outburst is a jet of energy and matter which was lucky enough to be flung away from the gravitational center of a black hole as opposed to pulled into its inescapable grasp.
The other theory is that it could be a massive supernova, although its brightness appears to suggest otherwise. Cygnus A already has a supermassive radio-emitting black hole named Cygnus X-1 at its center, so this discovery could mean that a second black hole has joined the galaxy thanks to a recent galactic merger. If that theory is confirmed, they would be the closest known pair of black holes ever discovered.