Discovery of massive black hole upends assumptions on galaxy formation

Astronomers have discovered a black hole that grew much more quickly than its host galaxy, a finding that calls into question assumptions about how galaxies developed.

The discovery of the black hole was originally announced in July this year. It was observed with the NASA Hubble Space Telescope, in the Sloan Digital Sky Survey and then by ESA’s XMM-Newton and NASA’s Chandra X-ray Observatory.

Now follow-up observations by Benny Trakhtenbrot, from ETH Zurich’s Institute for Astronomy, and an international team of astrophysicists, using the 10 metre Keck telescope in Hawaii has thrown up some surprising results.

The data, collected with a new instrument, reveals the giant black hole in an otherwise normal, distant galaxy, called CID-947.

It is so far away, that the observations are of when the Universe was less than two billion years old (it is now almost 14 billion years since the Big Bang).

CID-947 has nearly seven billion solar masses, making it one of the most massive black holes ever discovered. But what surprised researchers was the galaxy’s mass.

“The measurements correspond to the mass of a typical galaxy,” says Trakhtenbrot. “We therefore have a gigantic black hole within a normal size galaxy.”

Most galaxies have a black hole at their centre that holds millions to billions of solar masses.

Until now, observations have indicated that the greater the number of stars present in the host galaxy, the bigger the black hole.

Scientists had assumed that the growth of black holes and the formation of stars go hand-in-hand, but these new results suggest that these processes work differently, at least in the early Universe.

Bill Condie

Bill Condie

Bill Condie is a science journalist based in Adelaide, Australia.

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