April 23, 2009

New Cosmic ‘Blob’ Puzzles Cosmologists

A team of astronomers in California recently discovered a giant cosmic "blob" that they believe to be a remnant from our universe's infancy.

Using a small army of the world's most advanced space and ground telescopes, scientists from the Carnegie Observatory in Pasadena California were able to essentially look back in time to a point when the universe was a mere 800 million years old.  Researchers have identified the object as an "extended Lyman-Alpha blob", a vague cosmological term used to describe a large body of gas that may be the forerunner of a new galaxy.

Truth be told, however, scientists don't really know what it is.

The heavenly blob is one of the most remote objects ever discovered by astronomers and its sheer distance strains the capabilities of even the most high-tech and modern telescopes available.  The faintness of the image produced by the telescopes has not permitted researchers to reach many conclusions about the physical nature and origins of the blob.

"The puzzle is "“ what is it?" says a bewildered Richard Ellis, an astronomer at the California Institute of Technology.  "Often a puzzle leads to a breakthrough.  My nose tells me that this object is rather special."

Appropriately, the obscure blob has been dubbed Himiko after a mysterious warrior queen of Japanese folklore.

What cosmologists do understand about Himiko is that it is enormous.  Stretching across some 55 thousand light years, the blob is comparable in size to the radius of the Milky Way and has a mass equivalent to about 40 billion of our Suns. 

At a time when the universe was only about 6 percent of its current age, this is an unexpectedly large size for any cosmic body.  According to the concordance model of Big Bang cosmology, the universe began with smaller objects that only later aggregated together to form larger cosmic bodies such as the larger galaxies and solar systems that exist today.  Other extended Lyman-Alpha blobs have typically been discovered from a time when the universe was some 2 to 3 billion years old "“ significantly later than the Himiko blob.

"I am very surprised by this discovery.  I have never imagined that such a large object could exist at this early stage of the universe's history"¦ This blob had a size of typical present-day galaxies when the age of the universe was only about 800 million years old!" explained the report's lead author, Masami Ouchi.

Himiko's extraordinary size and brightness initially caused the astronomers to think they were picking up interference from a nearby galaxy.  "We hesitated to spend our precious telescope time by taking spectra of this weird candidate," said Ouchi.  "We never believed that this bright and large source was a real distant object.  We thought it was a foreground interloper contaminating our galaxy sample."

The further astronomers look into space, the further back in time they go, plunging deeper and deeper into the universe's past looking for clues about its origin.  From more than 12.9 billion years ago, Himiko is the fourth oldest cosmic object ever observed by scientists.

"One of the puzzling things about Himiko is that it is so exceptional," said Alan Dressler, another member of the team.  "If this was the discovery of a class of objects that are ancestors of today's galaxies, there should be many more smaller ones already found "“ a continuous distribution.  Because this object is, to this point, one-of-a-kind, it makes is very hard to fit it into the prevailing model of how normal galaxies were assembled.  On the other hand, that's what makes it interesting!"


Image Caption: This image of the Himiko object is a composite and in false color. The thick horizontal bar at the lower right corner presents a size of 10 thousand light year. Credit: M. Ouchi et al.


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