Scientists baffled by huge black hole discovered in tiny galaxy

Nov 29, 2012
Anna McKie

'This is a really oddball galaxy,' says astronomer of findings that might force revolution in galaxy evolution theories


A HUGE black hole has been discovered at the centre of a small galaxy, confounding scientists who have until now believed supermassive black holes were only found in very large galaxies.

Astronomers, using the Hobby-Eberly Telescope in Texas and studying data from the Hubble Space Telescope, discovered that galaxy NGC 1277, which is just a quarter of the size of our own Milky Way, hosts a black hole with a mass of 17 billion suns.

A black hole typically 'weighs in' at around 0.1 per cent of its host galaxy's mass. However, NGC 1277's black hole is a relatively enormous 14 per cent.

Dr Karl Gebhardt of the University of Texas at Austin, who is an author of the study published today in the journal Nature, said: "This is a really oddball galaxy. It's almost all black hole."

Gebhardt believes the new discovery could mean astronomers have to rethink how galaxies evolve.

It was thought that galaxies and their black holes grew at similar rates during that part of a galaxy's life-cycle during which stars are formed. When a black hole's mass became large enough, the huge wind generated would force star-forming materials out of the galaxy, creating a kind of 'galactic equilibrium': no more stars would form, but at the same time there would be no new material to add to the black hole's mass.

However, it appears NGC 1277's black hole kept on growing.

Astronomer Jenny Greene of Princeton University, New Jersey, told that the discovery could also change the way scientists estimate the size of black holes.

When dealing with black holes in a distant galaxy, such as NGC 1277, astronomers take average measurements from the nearby stars' speeds: their "velocity dispersion". But, according to Greene, NGC 1277 shows the method may be causing scientists to underestimate the true mass of black holes.

Gebhardt and his colleagues have identified five other small galaxies that exhibit velocity dispersion like NGC 1277. If these galaxies also contain unusually large black holes, scientists will be forced to change their earlier theories.

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