The debris from a colossal cosmic explosion in a galaxy hundreds of millions of light-years away is no ordinary supernova.
According to a new analysis of the distant event, it was triggered by a merger between two objects, one of which was compact, either a black hole or a neutron star. The evidence of this event, called VT J121001+495647, is the first observed supernova of its kind.
"Theorists had predicted that this could happen," said astronomer Dillon Dong of Caltech, "but this is the first time we've actually seen such an event."
The supernova was discovered during a 2017 radio survey of the sky, called the Very Large Array Sky Survey (VLASS). During its sweep, the VLA picked up a very brightly glowing radio source that had not appeared in an earlier survey conducted using the same telescope.
Follow-up observations, using both the VLA and the W.M. Keck Observatory which studies the sky in optical and infrared wavelengths, revealed that the radio source did indeed exist, and was consistent with an expanding supernova remnant interacting with dust and gas.
As the fast-moving supernova material expands into that material, shocks and heat are generated, producing electromagnetic radiation so bright that we can detect it, even from other galaxies. Dong and his team traced VT J121001+4959647 to a dwarf galaxy 480 million light-years away.
They also studied archival data of that region of the sky, to determine when VT J121001+4959647 may have started to brighten. They found a burst of soft X-rays picked up in 2014 by the Monitor of All Sky X-ray Image (MAXI) instrument on the International Space Station.