Artist's impression of the new source HLX-1 (represented by the light blue object to the lower right of the galactic bulge) in the periphery of the edge-on spiral galaxy ESO 243-49. This is the first strong evidence for the existence of intermediate mass black holes.
Credit: Heidi Sagerud
SYDNEY: Astronomers have detected the first strong evidence for a new class of 'mid-size' black holes that could help prove how supermassive black holes form.
Until now, black holes have either been supermassive – millions to billions of times the mass of the Sun — or stellar mass black holes, small black holes that form from the death of stars.
Now, astrophysicists from the Centre d'Etude Spatiale des Rayonnements in Toulouse, France and the University of Leicester, UK and the have found a middle-mass black hole, dubbed Hyper-Luminous X-ray source 1 or HLX-1.
The black hole, which is 290 million light years away, is at least 500 times the mass of the Sun.
Missing link
The find, reported today in the journal Nature, may be the missing link to theories on how supermassive black holes form. No-one knows how supermassive black holes, such as the one at the centre of the Milky Way galaxy, are created. One theory is that they grow from the merger of smaller black holes.
But until now, no one had found any direct evidence of the intermediate-mass black holes thought to be the building blocks of supermassive black holes.
"The identification of HLX-1 is therefore an important step towards a better understanding of the formation of the supermassive black holes that exist at the centre of the Milky Way and other galaxies," said the study's lead author, astrophysicist Sean Farrell from the University of Leicester.
The team first noticed interesting X-ray emissions from the galaxy ESO 243-49, using observations made on 23 November 2004 with the European Space Agency's XMM-Newton X-ray space telescope. They observed the galaxy again on the 28 November 2008.
The researchers noted that the X-ray brightness dimmed by more than 30%. Because of the variation in brightness and spectral signature of the X-rays, the team concluded they must originate from a single source, probably a black hole.
Strongest evidence yet
Candidates for intermediate mass black holes have been discovered before, but it remained inconclusive if these sources were really stellar mass black holes or some other source of X-rays, such as a bright quasar in the background.
"Where our object stands out is that it is about 10 times brighter than the previous record holder in this category, which makes it the best candidate for an intermediate mass black hole," Farrell said.
Australian astrophysicist Scott Croom, from the University of Sydney said the research was "convincing". But he believed it "couldn't definitely be ruled out" that HLX-1 was in fact a background source not a black hole. As the researchers point out in their paper, there was still a 9% chance the object was in the background, Croom said.
Croom said that he would expect this kind of black hole to be more towards the centre of the galaxy. If HLX-1 was an intermediate sized black hole, it would lend weight to other candidate X-ray sources also being intermediate mass holes, he said.
"It's a neat bit of work to find [an intermediate-mass black hole] but what we really need is to find a whole lot more to figure out how these things evolve," he added.
black holes, real or fantasy?
It used to be black and it used to eat everything. Neither is true now. Now they look for it as the one of the brightest things in the sky in the x-ray band, across a certain distance, with a certain mass and it eats nothing. The story is always changing but the abstract math which brought this about stays the same. People still eat this silliness up as if it were their favorite pastry. Very many intelligent people do not believe this gibberish and face scorn, academic banishment and public ridicule for being willing only to question an idea which has been placed at the alter of so called modern science. We are in a golden age of technology with a medieval control structure deciding what the truth is and what is not allowed to be discussed. That is religion and not science to me. Take the time to disprove the math of Stephen Crothers in his letter to Gillessen, Genzel and Eisenhauer, (http://www.sjcrothers.plasmaresources.com/dialogue.pdf), concerning a super massive black hole at Sagittarius A*, (http://www.space.com/scienceastronomy/081209-blackhole-stars.html#comments).
If all you do is act derisively and investigate nothing while laughing at the idea, do not flatter yourself: that is not science.
re: black holes, real or fantasty?
The paper clearly states that this object is "accreting" material, so it is definitely eating something! Their case for there being a black hole is based on the theories of Eddington, which shows that the maximum luminosity attainable by a feeding black hole is defined by its mass. As the mass of the object has to be >500 times the mass of the Sun, and as they showed that it can't be multiple sources, it must be a black hole. Can you come up with an answer to how the neutron degeneracy pressure can withstand the gravitational pressure of an object this mass?