London, Oct 17 : Astronomers have found two very different galaxies in the distant Universe involved in a spectacular collision, which reveal that colossal black holes were common in the early Universe.
New observations made with the Submillimeter Array of telescopes in Hawaii suggest that black holes that were thought to exist in many, if not all, galaxies, were common even in the early Universe, when galaxies were just beginning to form.
4C60.07 - the first of the galaxies to be discovered - came to astronomers' attention because of its bright radio emission.
This radio signature is one telltale sign of a quasar - a black hole, spinning rapidly, feeding on its parent galaxy.
A new image captures the moment, approximately 12 billion years ago, when this galaxy ripped a stream of dusty gas from a neighbour.
When 4C60.07 was first studied, astronomers thought that gas surrounding its black hole was undergoing a burst of star formation, turning virgin gas into stars at a remarkable rate - the equivalent of 5,000 of our Suns every year.
This prodigious activity was revealed by the infrared glow from smoky debris in which the largest stars rapidly die.
The latest research, exploiting the keen vision possible with the Submillimeter Array, revealed a surprise: 4C60.07 is not forming stars after all.
Indeed, its stars may well be relatively old and quiescent. Instead, the prodigious star formation is taking place in a previously unknown companion galaxy, which is rich in gas and deeply enshrouded in dust, and has another colossal black hole glowing as its centre.
"This new image reveals two galaxies where we only expected to find one," said Professor Rob Ivison at the Science and Technology Facilities Council's UK Astronomy Technology Centre in Edinburgh, lead author of the study.
"Remarkably, both galaxies contain super-massive black holes, each capable of powering a billion, billion, billion light bulbs," he added.
"The implications are wide reaching: you can't help wondering how many other colossal black holes may be lurking unseen in the distant Universe?" he further added.
"It seems we were led to pluck the radio galaxy and its neighbour from the countless millions of objects in the sky because they are involved in a rare collision," said Ivison.
Due to the finite speed of light, the two galaxies are seen as they collided in the distant past, less than 2 billion years after the Big Bang.
By now, the galaxies will have merged to create a football-shaped elliptical galaxy. Their black holes are likely to have merged to form a single monstrously large black hole.