Thirteen years ago, my colleague Prof Peter Meikle came into my office and asked “Dave, you know something about merging galaxies?”
“Yes,” I replied.
“Well,” he said, “something odd has happened in Arp 299.”
Arp 299 is a merger between two galaxies which has resulted in a burst of star formation and fuel falling onto the supermassive black hole in at least one of the galactic nuclei. What Peter had found was that one of the galactic nuclei had suddenly got much brighter in the near-infrared, but this was not visible at optical wavelengths. This meant that whatever had happened was enshrouded by a lot of dust so that only longer wavelength radiation from the event could reach us.
What ensued was a campaign using many telescopes on the ground and in space to monitor this event and try to work out what was causing it.
At first we thought it was a dust enshrouded supernova, which is understandable given the starburst going on in Arp299, but as time wore on, and the nucleus continued to shine brighter in the near-infrared, it became clear that whatever the power source might be, it was more powerful than even a luminous supernova.
Eventually Seppo Matilla, who was leading the project, got some deep high resolution radio observations which showed a new jet of radio emission in this nucleus. This is a clear signature of emission from a supermassive black hole, and the energetics suggested that a star about twice the mass of the sun was being ripped apart and swallowed by a supermassive black hole in this nucleus, with about 20 million times the mass of the sun. This is what is known as a Tidal Disruption Event.
You can read more about this on Imperial’s website:
and can also see our actual paper in Science: