Light from a black hole?
Michael Coughlin, Assistant Professor in the School of Physics and Astronomy and a member of the Minnesota Institute for Astrophysics, is part of an international team of astronomers who have seen what might be the first light ever detected from a black hole merger.
If black holes don't emit light, how could the merger of two black holes create light? Some theorists have posited that in certain situations the merger of black holes could cause an explosion of gas that could be observed by a ground based telescope.
Thanks to the Laser Interferometer Gravitational-wave Observatory (LIGO), which has been observing mergers of black holes since the Nobel-Prize winning break-through discovery of gravitational waves in 2015, astrophysicists now know where to look for such a light source. The Zwicky Transient Facility (ZTF) at the Palomar Observatory has spotted what might be a flare of light from a pair of coalescing black holes. The black hole merger was first witnessed by LIGO and the European Virgo detector on May 21, 2019. As the black holes merged, they sent out gravitational waves.
Michael Coughlin is a co-author on a paper which used ZTF's robotic survey of the sky to look for light from the 2019 merger. They found a quasar--a very distant celestial body thought to possibly contain super massive black holes--which was pinpointed to the same location as the 2019 event.
The mechanism which is thought to produce the explosion is called a "kicked black hole." There is an accretion disc around super massive black holes that contains material from dead stars and gas. There may be many black holes swirling in this mass. When the two black holes merge, the new, now-larger black hole experiences a kick that sends it off in a random direction, and it plows through the gas in the accretion disk. This kicked black hole ignited the gas, causing the flare that was visible on earth.