Galactic freak could reveal how galaxies form

March 25th, 2009 - 1:26 pm ICT by IANS  

Sydney, March 25 (IANS) Astronomers have located a galactic freak, an extremely rare ultra-compact dwarf galaxy, that could be the missing link in understanding how galaxies and their clusters evolve.
The dwarf galaxy, which is the closest yet found to Earth, is far brighter and more massive than the clusters of stars that usually surround galaxies, and was born in the very early stages of the formation of the universe.

Swinburne University astronomers George Hau and Duncan Forbes said the galaxy was discovered when using the mighty 10-metre Keck II telescope on the mountain of Mauna Kea in Hawaii.

“We were observing the properties of star clusters surrounding the well-known Sombrero Galaxy, when we detected this compact object that was far brighter than any of its companions,” Hau said.

“It was only the size of a star cluster - which typically contain about one million stars - but it shone as brightly as a small galaxy. This indicated the object was an ultra-compact dwarf galaxy, a very unusual object, possibly containing 10 million stars.”

How such rare phenomena form is a mystery, but the discovery of SUCD1, as the object has been named, has presented the perfect opportunity to find out, and to fill in another vital chapter in galactic evolution.

Another unusual aspect of the ultra-compact dwarf galaxy is that it is very old - perhaps 10 billion years, indicating it was formed in the early stages of the universe, when things were all the more violent and energetic.

Furthermore it appears to consist mainly of stars, rather than the still-enigmatic dark matter, which dominates the mass of most galaxies.

Small it may be, but SUCD1 is hardly peaceful, spitting out a powerful stream of X-rays. The team believes this to be the first time that X-ray emissions have been clearly detected from an ultra-compact dwarf object, said a Swinburne release.

The discovery was published in the March Monthly Notices of the Royal Astronomical Society.

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