Hundreds of 'supermassive' black holes discovered

A supermassive black hole is a black hole with a mass of an order of magnitude between 105 and 1010 (hundreds of thousands and tens of billions) of solar masses. It is currently thought that most, if not all galaxies, including the Milky Way, contain supermassive black holes at their galactic centers.

There appears to be a link between the mass of the supermassive black hole in the center of a galaxy and the morphology of the galaxy itself. This manifests as a correlation between the mass of the spheroid (the bulge of spiral galaxies, and the whole galaxy for ellipticals) and the mass of the supermassive black hole. There is an even tighter correlation between the black hole mass and the velocity dispersion of the spheroid. The explanation for this correlation remains an unsolved problem in astrophysics.

Black holes are among the most powerful forces in the Universe. They are believed to be concentrated fields of gravity which are so powerful that nothing, not even light, can escape them.

An international team of astronomers have unexpectedly found hundreds of expanding "supermassive" black holes buried deep inside galaxies billions of light years from Earth.

The astounding discovery is the first direct evidence that most, perhaps all, huge galaxies in the far reaches of the universe generated cavernous black holes during their youth, when about 3.5 billion years old.

Scientists generally agree that the universe as we perceive it came into being about 14 billion years ago.

The findings more than double the total number of black holes known to exist at that distance, and suggest that there were hundreds of millions more growing in the early universe.

Astronomers have long assumed that there were far more so-called "active" black holes than had been observed, but were unable to find any trace of them.

These supermassive entities are known as high-energy quasars, a form of black hole, found in a young galaxies, that is surrounded by a thick halo of gas and dust which shoot off X-rays as they are sucked into the void.

The X-rays, which can be detected as a general glow in space even when the quasars themselves cannot be seen, are what tipped off the scientists that they had stumbled across something extraordinary.

At 9 to 10 billion light years distant, what scientists see today existed some 10 billion years ago, when the universe was still a fledgling between 2.5 and 4.5 billion years old.

The newfound quasars will help answer fundamental questions about how massive galaxies evolve. Astronomers now know, for example, that most of these galaxies steadily generate stars and black holes simultaneously until the latter become too big and impede star formation.

The observations also suggest that collisions between galaxies may not, as once thought, play a critical role in galaxy evolution.

Two telescopes were needed to see the black holes. One is NASA's Spitzer space telescope, which picks up infrared light, and the other is the Chandra telescope, which relays X-ray data.

The findings will be published next month in the US journal Astrophysical Journal.