Researchers find two supermassive black holes getting closer to merging

PKS 2131-021 is now the second known candidate for a pair of supermassive black holes caught in the act of merging. Each of the two black holes in PKS 2131-021 is estimated to be a few hundred million times the mass of our Sun.

A team of astronomers observing a supermassive black hole 9 billion light-years away have reported signs that it has a companion black hole orbiting around it. The enormous duo – called a binary – circle one another about every two years and the pair will merge in roughly 10,000 years.

Researchers at Caltech in Pasadena have been monitoring more than 1,000 blazars- supermassive black holes with jets oriented toward Earth - with the Owens Valley Radio Observatory in Northern California for 13 years as part of a general study of blazar behaviour.

They noticed a blazar named PKS 2131-021 exhibiting strange behaviour - its brightness showing regular ups and downs as predictably as the ticking of a clock. Researchers believe that this regular variation is the result of a second black hole tugging on the first as they orbit each other.

As the black holes spiral toward each other, they increasingly disturb the fabric of space and time, sending out gravitational waves across the universe, the researchers say.

Two black holes are spiraling toward a collision. Astronomers found a supermassive black hole 9 billion light-years away with another black hole orbiting around it. As that orbit shrinks, the pair - called a binary - get closer to merging. https://t.co/b9yqLpy429 pic.twitter.com/GRn4hLSBf3

— NASA JPL (@NASAJPL) February 25, 2022

PKS 2131-021 is now the second known candidate for a pair of supermassive black holes caught in the act of merging. Each of the two black holes in PKS 2131-021 is estimated to be a few hundred million times the mass of our Sun.

"This work is a testament to the importance of perseverance. It took 45 years of radio observations to produce this result. Small teams, at different observatories across the country, took data week in and week out, month in and month out, to make this possible," says Joseph Lazio at NASA's Jet Propulsion Laboratory (JPL) in Southern California.

Lazio and Michele Vallisneri, both astrophysicists at NASA's JPL, provided insight into how supermassive black holes behave in a binary system and how to interpret the radio data.

More details can be found here.