Pointing the Very Large Array (VLA) at a famous galaxy for the first time in two decades, a team of astronomers got a big surprise, discovering that a bright new object had appeared near the galaxy’s core. The object, the scientists concluded, is either a very rare type of supernova explosion or, more likely, an outburst from a second supermassive black hole closely orbiting the galaxy’s primary, central supermassive black hole.
The astronomers observed Cygnus A, a well-known and often-studied galaxy discovered by radio-astronomy pioneer Grote Reber in 1939. The radio discovery was matched to a visible-light image in 1951, and the galaxy, some 800 million light-years from Earth, was an early target of the VLA after its completion in the early 1980s. The VLA’s upgrade that was completed in 2012 made it a much more powerful telescope. Daniel and Rick Perley, along with Vivek Dhawan, and Chris Carilli, both of NRAO, began the new observations in 2015, and continued them in 2016.
The scientists then observed Cygnus A with the Very Long Baseline Array (VLBA) in November of 2016, clearly detecting the new object. What is the new object? Based on its characteristics, the astronomers concluded it must be either a supernova explosion or an outburst from a second supermassive black hole near the galaxy’s center. While they want to watch the object’s future behavior to make sure, they pointed out that the object has remained too bright for too long to be consistent with any known type of supernova.