doi:10.1038/nindia.2017.135 Published online 25 October 2017
Astrophysicists have detected a pair of supermassive black holes in a galaxy 400 million light-years from Earth. The black holes, which have a combined mass of about 40 million Suns, orbit each other.
This observation can help better understand how galaxies form and evolve.
All large galaxies harbour a supermassive black hole at their centres. Although theories have long predicted the presence of supermassive binary black holes, they are difficult to detect.
Analysing data beamed back by an array of US-based radio telescopes, scientists led by Preeti Kharb from the National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune in India and from the Rochester Institute of Technology in the USA detected the pair of black holes at the heart of a spiral galaxy known as NGC 7674.
Analyses suggest that the binary has an orbital period of about 100,000 years. The galaxy in which the black hole pair was found possesses a 0.7 kiloparsec Z-shaped radio jet. Detection of the pair of supermassive black holes also confirms a theoretical prediction that such binaries should be present in so-called Z-shaped radio sources.
The black hole pair, separated from each other over a distance of less than one light year, supports the idea that galaxies evolve through mergers of galaxies, leaving a pair supermassive black holes at their centres, says Kharb.
1. Kharb, P. et al. A candidate sub-parsec binary black hole in the Seyfert galaxy NGC 7674. Nat. Astron. (2017). doi: 10.1038/s41550-017-0256-4