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Fastest-growing black hole ‘hiding in plain sight’ — 7,000 times brighter than Milky Way


Located some seven billion light-years away, the black hole — which has been given the name of “SMSS J114447.77-430859.3”, or “J1144” — appears as a quasar. These are extremely bright active galactic nuclei with supermassive black holes at their hearts. As gas swirls around and into the black hole, friction causes it to heat up, emitting vast quantities of electromagnetic radiation. According to the researchers, the mass of J1144 is a whopping 2.6 billion times that of the Sun — and it is growing by the equivalent of an Earth’s worth of material every second.

Given that J1144 is so bright, you may well ask how astronomers could have missed it.

The answer lies in the black hole’s location relative to the Milky Way — in particular, how it appears in the sky just 18 degrees above the galactic plane.

Surveys looking for quasars tend to stop around 20 degrees shy of the Milky Way’s disk, beyond which point it becomes hard to hunt for objects out in the wider universe for all the stars from our galaxy getting in the way.

Mostly because of this, J1144 has managed to avoid being picked out by astronomers looking for quasars — and was found in other ways.

Paper author and astronomer Dr Christopher Onken of the Australian National University (ANU) told ScienceAlert: “A bit of historical bad luck has become our good luck.

“Searches for distant objects get very difficult when you look close to the disk of the Milky Way — there are so many foreground stars that it’s very hard to find the rare background sources.

“Another team used an ultraviolet satellite to search for these luminous objects across the whole sky, but J1144 fell into a small gap in their coverage.

“But the source is bright enough that it appears in photographs taken of the sky as far back as 1901, so it’s definitely a case of hiding in plain sight.”

READ MORE: UK space probe spots tsunami-like ‘starquake’ in Milky Way

Paper co-author and fellow ANU astronomer Professor Christin Wolf told ScienceAlert: “This black hole is such an outlier that — while you should never say never — I don’t believe we will find another one like this.”

“We are fairly confident this record will not be broken. We have essentially run out of the sky where objects like this could be hiding.”

However, the team said, the discovery has encouraged them to undertake a renewed hunt for bright quasars — with the team having already confirmed 80 new ones and hundreds more candidates awaiting analysis and confirmation.

This, the researchers added, could mean that the astronomical community is close to having a complete census of bright quasars in the relatively recent, visible Universe.

Regarding the other fresh discoveries, Dr Onken said: “None of them are as bright as J1144.

“But they’ll help paint a more complete picture of how common this rapid growth phase might be, and that will help us to understand the physical mechanism behind it.”

This mechanism, he added, could be “rare collisions between enormous galaxies, or something special about the environment right around the black hole, or actually about the black hole itself

“For example, a rapidly spinning black hole can release much more energy from the matter it accretes than one that is hardly spinning at all.”

Alongside this, Dr Onken explained, analysing the bright light coming from quasars can help reveal the nature of the gas that populates intergalactic space.

Analysing this gas — specifically how it flows around the Milky Way — can give astronomers a better understanding of three-dimensional movements within the universe.

A preprint of the researchers’ article, which has been accepted for inclusion in the journal Publications of the Astronomical Society of Australia but has not yet been peer-reviewed, can be read on the arXiv repository.



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