Scientists discover supermassive black holes 28 billion times bigger than the Sun

A pair of supermassive black holes have been discovered in a galaxy that is 750 million light-years away.

In the galaxy called B2 0402+379, the couple of massive black holes have a combined mass that is a huge 28 billion times the mass of the Sun.

Although some black holes can exceed this on their own, the two recently found are certainly the heftiest black hole binary.

Astronomers have been researching what occurs when the two come together and can do this thanks to several strange characteristics - and this research has been published in The Astrophysical Journal.

But exactly how they grow to a supermassive size remains a mystery. What we do know is how small black holes are formed and this is down to the collapsed cores of stars.

Growth can occur for these stellar mass black holes by crashing into each other.

With this logic, it could be assumed that if colliding and merging is how small black holes are formed, then a similar method happens for the supermassive ones too.

However, this theory has a flaw in what is known as the final parsec problem due to black hole binaries - the system consisting of two black holes in close orbit around each other - getting rid of their orbital momentum by shifting onto gas stars nearby that shoot off into the unknown and lose it in the form of gravitational waves, Science Alert reported.

The smaller the orbital distance, the smaller the bandwidth of space to shed their energy - so at a distance of 3.2 light-years there isn't enough space to shed further momentum, and orbital decay is stabilised and halted.

A team led by astrophysicist Tirth Surti of Stanford University believe the galaxy B2 0402+379 could be an instance of the final parsec problem taking place.

Archival data collected by the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope has been examined by the team to understand the properties of the two huge black holes.

This is how they found the galaxy used to be a group of galaxies which then crushed together and the blackholes mass of the binary was a whopping 28 solar masses.

As a result of the galaxies smashing into one another, the supermassive black hole is what is left of the cluster of black holes.

The distance between the two black holes was also calculated to be 24 light-years, and it appears orbital decay has stalled and this distance has remained for 3 million years in a stable orbit.

What this supermassive find suggests is that high mass plays a pivotal part in the final parsec problem, the theory researchers are working with is that there are no stars left where the orbital momentum can be transferred to, while the lack of stars is down to the amount that shot off from the last orbital decay of the binary.

"Normally it seems that galaxies with lighter black hole pairs have enough stars and mass to drive the two together quickly," astrophysicist Roger Romani of Stanford University said.

"Since this pair is so heavy it required lots of stars and gas to get the job done. But the binary has scoured the central galaxy of such matter, leaving it stalled and accessible for our study."

After learning how on rare occasions black holes can grow larger than the binary's combined mass, it doesn't look like the galaxy's nuclear binary is shedding orbital momentum anytime soon.

The creation of a third supermassive blackhole is possible if another galaxy merge were to happen - though the cluster of galaxies have already come together to make B2 0402+379 so this seems unlikely.

But, material in the galaxy could hold the key as to how the two supermassive black holes could merge.

"We're looking forward to follow-up investigations of B2 0402+379's core where we'll look at how much gas is present," Tirth added.

"This should give us more insight into whether the supermassive black holes can eventually merge or if they will stay stranded as a binary."

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