American astronomers, utilizing the archival data from the Gemini North telescope, have discovered the heaviest supermassive black hole pair known to date, with a combined mass of 28 billion times that of the sun. This recent study aids scientists in unraveling a long-standing mystery: why the merger of supermassive black holes appears to be exceedingly rare in the universe. The findings are detailed in the latest issue of The Astrophysical Journal.
Scientists have long predicted the merger of two supermassive black holes, but direct observation of this phenomenon has remained elusive.
Image Source: National Science Foundation, USA
The research team conducted an analysis of the supermassive black hole pair located within the elliptical galaxy B2 0402+379. This is the only pair of supermassive black holes analyzed in sufficient detail, with a mere 24 light-years separating the two black holes. The close proximity between these two black holes suggests a powerful merger is imminent. However, further investigation revealed that these black holes have remained at this distance for over 3 billion years.
Professor Roger Romani, co-author of the latest paper and a physics professor at Stanford University, explained that to better understand the dynamics of this system and the reasons for their non-merger, they examined archive data from the Gemini North Telescope. By determining the velocities of stars near the black holes, they inferred that the combined "weight" of this black hole pair is 280 billion times that of the Sun, making it the heaviest black hole pair ever measured.
The research team stated that this measurement not only provides valuable information for studying the formation of binary black hole systems and the history of their host galaxies but also supports a long-standing theory that the mass of supermassive black hole pairs is a crucial factor preventing their merger.
Typically, galaxies with lighter black hole pairs seem to have enough stars and mass to facilitate their merger, as evidenced by the 2015 detection of gravitational waves from the merger of stellar-mass black holes. However, due to the extreme weight of this black hole pair, a substantial amount of stars and gas is required for the merger. Given the lack of sufficient material within the B2 0402+379 galaxy, the merger of this black hole pair has stalled.
Romani pointed out that whether these black holes will eventually merge on a timescale of millions of years remains to be determined. If they do merge, the strength of the gravitational waves produced would be a hundred million times greater than those generated by the merger of stellar-mass black holes.
