Ginormous black hole that outgrew its galaxy discovered

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Astronomers have discovered what they classify as a ginormous black hole in the early universe – just two billion years after the big bang – in a galaxy that is of normal size. Researchers have also revealed that the uniqueness about the find is that the black hole has outgrew its host galaxy.

Discovered by an international research group including astronomers from Yale University, ETH Zurich, the Max-Planck Institute in Germany, Harvard University, the University of Hawaii, INAF-Osservatorio Astronomico di Roma, and Oxford University, the black hole resides in galaxy CID-947. Researchers say that the black hole is among the most massive black holes ever found. It measures nearly 7 billion solar masses (a solar mass is equivalent to the mass of our Sun).

The discovery was made during a project to map the growth of supermassive black holes across cosmic time and is in stark contrast to observations about black holes and host galaxies. It has long been established that black holes and their host galaxies expand at the same rate; however the latest finding challenge previous notions about the way host galaxies grow in relation to black holes, it also challenges earlier suggestions that the radiation emitted by expanding black holes curtails the creation of stars.

Credit: Michael S. Helfenbein

Credit: Michael S. Helfenbein

The Astronomers said that their survey was designed to observe the average objects, not the exotic ones and they were targeting moderate black holes that inhabit typical galaxies today.

“It was quite a shock to see such a ginormous black hole in such a deep field”, said C. Megan Urry, Yale’s Israel Munson Professor of Astrophysics and co-author of a study about the phenomenon in the journal Science.

Deep-field surveys are intended to look at faint galaxies; they point at small areas of the sky for a longer period of time, meaning the total volume of space being sampled is relatively small.

However, it was the mass of the surrounding galaxy that most surprised the research team. “The measurements correspond to the mass of a typical galaxy,” said lead author Benny Trakhtenbrot, a researcher at ETH Zurich’s Institute for Astronomy. “We therefore have a gigantic black hole within a normal-size galaxy.”

Stars were still forming in CID-947, the researchers said, and the galaxy could continue to grow. They said CID-947 could be a precursor of the most extreme, massive systems observed in today’s local universe, such as the galaxy NGC 1277 in the Perseus constellation, 220 million light years from the Milky Way. But if so, they said, the growth of the black hole still greatly anticipated the growth of the surrounding galaxy, contrary to what astronomers thought previously.

Urry and her colleagues credited the W.M. Keck Observatory in Hawaii and the Chandra COSMOS legacy survey in aiding the team’s work. “The sensitivity and versatility of Keck’s new infrared spectrometer, MOSFIRE, was critical to this discovery,” Urry said.