SPACE.com -- NASAs powerful Chandra has evidence of a black hole residing in thegalaxy M82

The home of the intermediate-sized black hole is an irregular disk galaxy M82 is located some 10 million light-years away in the constellation Ursa Major. M82 is the classic example of a starburst galaxy, where each year its nucleus alone co nverts 10 sun

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	NASAs powerful Chandra has evidence of a black hole residing in thegalaxy M82 By Ray Villard Special to SPACE.com posted: 06:45 pm ET 25 September 2000

If he is correct, astronomers may be witnessing for the first time how a galaxy "grows" a single monstrous supermassive black hole at its center. "That is why this finding is so important, it is the prototype of something we’ve never seen before," said Griffiths.

The new object could offers a window into the early universe, where growing black holes may have been common, as evident in the plethora of mature black holes today. This is particularly true of quasars -- brilliant well-fed supermassive black holes that began to appear a billion years after the universe’s birth in the Big Bang. "This may be the typical amount of time it takes for a galaxy to grow a supermassive black hole," said Griffiths.

M 82 is a late bloomer when it comes to cultivating its own central black hole. The galaxy is so small, it could fit inside the hub of our Milky Way." This is an immature galaxy. It has a lot of unprocessed gas," said Griffiths. "Small galaxies like this one have existed for the history of the universe without growing a central black hole."

A portrait of irregular galaxy M 82 (left) and companion galaxy M 81(right). M82's "grand spiral" design and its irregular shape may have been caused by a near collision between the two galaxies 100 million years ago. In this view they are separated by 150,000 light-years, or only 1.5 times the diameter of our Milky Way Galaxy. They are located 10 million light-years away in the constellation Ursa Major.

M 82 is known as a starburst galaxy where stars are being formed at a furious rate due to compression of interstellar gas. This was triggered by an encounter with companion galaxy M 81 100 million years ago. The galaxy now has a striking filamentary structure indicative of a firestorm of star birth.

Griffiths sketches a scenario where the seed black hole bulked-up inside one of the galaxy’s massive "super-star clusters" by the explosion of a single star. After its birth, the baby black hole continued engorging itself on interstellar gas that was constantly ejected by all the massive young, hot stars in the supercluster. "If the initial black hole has been accreting a millionth of a solar mass per year, then it would have grown to at least a hundred solar masses by now," Griffiths explained.

And the black hole is still growing, as evident by the gale of X-rays it unleashes due to voracious feeding.

Griffiths predicts that, like a monarch ascending to a throne, the black hole will eventually settle into the center of the galaxy to gravitationally rule the motions of the myriad stars as a fully grown supermassive black hole.

"It’s very interesting the black hole is not in the center but will eventually find its way to the center," added veteran black hole hunter Holland Ford of JHU. " This bears out the idea that black holes grow through mergers."

As far back as the 1970s astronomers suspected something funny was happening in M 82 when the first pioneering X-ray space observatories picked up a torrent of X-rays from the small galaxy. Even back then astronomers speculated there could be a single beefy black hole or a binary star where a small black hole is cannibalizing a companion star.

Observations in 1998 with the Japanese Advanced Satellite for Cosmology and Astrophysics (ASCA) telescope by Griffiths and Andrew Ptak of Carnegie, found the object was 10 times as bright as a normal X-ray star. They correctly estimated an "intermediate-class" black hole mass of 460 suns. "But we couldn’t be absolutely sure, we couldn’t tell where it was," said Griffiths. Nor could they clearly rule out alternative explanations such as a cluster of several stellar black holes or an undernourished supermassive black hole.

Chandra’s powerfully sharp vision settled the mystery. "We had speculation on top of speculation," said Griffiths. "Chandra nailed it by removing at least one level of speculation."

Much more research remains to be done, but this is generally seen as an intriguing new clue to the origin and evolution of black holes. "Astronomers are always skeptical of news things, but this one’s really neat," said Van Der Marel.

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