Astronomers Discovered Pairs of Supermassive Black Holes

Pablo Tucker
July 12, 2019

For all the advances in astronomy in mankind's history, scientists are still very much in the dark when it comes to black hole mergers, and nobody really knows what happens when they meet.

Supermassive black holes are usually found at the center of large galaxies, including our own Milky Way. The discovery provides an anchor point for estimating how many supermassive black hole pairs are within detection distance of Earth. The pair is likely belching gravitational waves into space already, but even if they are, we wouldn't be able to detect them for billions of years.

An global team of astronomers using NASA's Hubble Space Telescope found a thin disk whirling around a supermassive black hole 130 million light-years away, but the disk shouldn't exist there based on current theories.

But that's where this discovery and gravitational waves come into things.

A Princeton-led team of astrophysicists has spotted a pair of supermassive black holes, roughly 2.5 billion light-years away, that are on a collision course (inset). But this particular black hole does have a disk of material zipping around it at 10% the speed of light (a casual 18,628 miles per second), turning current models on their head.

Indeed, even before the destined collision, the gravitational waves exuding from the supermassive black hole pair will dwarf those recently recognized from the mergers of a lot smaller black holes and neutron stars.

"The type of disc we see is a scaled-down quasar that we did not expect to exist", Stefano Bianchi, first author of a new paper on the black hole published Monthly Notices of the Royal Astronomical Society, said in a statement.

Also, the disk is so deeply embedded in the black hole's intense gravitational field that the light from the gas disk is modified, giving astronomers a unique look at the dynamic processes close to a black hole.

This puzzle is dubbed the "final-parsec problem".

The gravitational waves generated by supermassive black hole pairs are outside the frequencies now observable by experiments such as LIGO and Virgo.

"If the gravitational wave background just isn't detected this might indicate that supermassive black holes merge exclusively over extremely long timescales, remaining as shut separation binaries for a lot of Hubble times, the so-called 'final-parsec problem, '" write the researchers.

Detecting the gravitational wave background using one of these pulsar timing arrays takes patience and plenty of monitored stars. If a passing gravitational wave stretches or compresses the space between Earth and the pulsar, the rhythm is slightly thrown off. The louder the background noise, the more massive the timing disruptions, and the quicker the detection will be made.

Although supermassive black holes can't be directly seen through optical telescope, they are surrounded by bright clumps of luminous stars and warm gas drawn in by their vast gravitational pull.

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