Scientists have used the National Science Foundation’s Very Long Baseline Array (VLBA) and its radio “vision” to detect the first known orbital motion from a pair of supermassive black holes in a galaxy 750 million light-years from Earth.
The two black holes have a collective mass of over 15 billion times that of the sun, and are only separated by approximately 24 light-years, an unusually close distance. This is the first pair of black holes which have been determined to move relative to each other. This phenomenon is known as a visual binary.
The fact that two of these black holes exist in one spot says that this galaxy merged with a different one at some point in the past. The two black holes are likely to merge together eventually, which will cause gravitational waves to ripple through the universe.
This merger will not occur until millions of years in the future, according to Karishma Bansal, a graduate student in the Department of Physics & Astronomy at the University of New Mexico.
The galaxy, known as 0402+379 after its sky location, and was first seen in 1995. The VLBA was used for further observation in 2003 and 2005, and was recently determined to have a pair of supermassive black holes.
The newest information concerning the two black holes was based on observations in 2009 and 2015, where it was discovered the two bodies are actually orbiting one another. Based on preliminary calculations, a single orbit between the two occurs approximately every 30,000 years. It was not until June 2017 that research confirmed the orbiting movement of the two black holes.
Surprisingly, astronomers believe that galaxy mergers which place two supermassive black holes in orbit with one another are a common occurrence in the universe.
The VLBA is a radio telescope which spans an entire continent, with 10 240-ton dish antennas going from Hawaii all the way to St. Croix in the Caribbean. The 10 antennas work together as a single telescope with more resolving power than any other in astronomy. Thanks to the power of this configuration, very fine measurements can be made, such as the ones used to detect 0402+379.