'Cosmic cannonballs' discovered in early universe

[sharmila banu.m]

New York, June 10: Astronomers have discovered what they claim is a new clutch of ultra-dense galaxies called "cosmic cannonballs" which formed soon after the Big Bang -- interestingly, there's no sign of today's compact galaxies.

According to a report in the 'New Scientist', a team at University of Hawaii has found the galaxies, which thrived in the early universe, at distances of 11 billion light years away, using the Keck II Telescope on Mauna Kea in Hawaii.

"They're packing essentially as much mass as the normal galaxies that we see around us today in a volume about a thousand times smaller," team leader Alan Stockton said.

In fact, the galaxies are so massive and some have such fragile disc shapes that they seem to have formed directly from the collapse of massive clouds of matter instead of being built up gradually by a series of mergers of smaller objects, according to the astronomers.

Galaxies of this sort are no longer around, but it's not clear what happened to them. Some have suggested that the galaxies disappeared because they collided with other galaxies to snowball into the large galaxies we see today.

But there may be problems with that explanation, Stockton says. The compact galaxies are so dense they are hard to modify by mergers with other galaxies, particularly lightweight ones, they said.

"The very compact galaxies here are essentially like little cannonballs. You can imagine merging a cannonball with, say, a pillow. Not much is going to happen to the cannonball. Of course, if two of these dense stellar systems do merge, the resulting remnant will have a larger effective radius than either of the merging galaxies.

"But it would require many such mergers to bring their sizes up to typical elliptical galaxies in the present-day universe -- probably more than is realistically feasible," Stockton said.

The findings are presented at a meeting of American Astronomical Society in California.



SOURCE - ZEENEWS