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Thursday, October 21, 2010

Most Distant Galaxy ever detected in the Universe


This collection of stars is so far away its light has taken more than 13 billion years to arrive at Earth.
Astronomers used the Very Large Telescope in Chile to follow up the Hubble observation and make the necessary detailed measurements.
They tell the journal Nature that we are seeing the galaxy as it was just 600 million years after the Big Bang.
"If you look at the object in the Hubble image, it really isn't much," said Dr Matt Lehnert of the Observatoire de Paris, France, and lead author on the Nature paper
"We really don't know much about it, but it looks like it is quite small - much, much smaller than our own Milky Way Galaxy. It's probably got only a tenth to a hundredth of the stars in the Milky Way. And that's part of the difficulty in observing it - if it's not big, it's not bright," he told BBC News.
Scientists are very keen to probe these great distances because they will learn how the early Universe evolved, and that will help them explain why the cosmos looks the way it does now.
In particular, they want to see more evidence for the very first populations of stars. These hot, blue giants would have grown out of the cold neutral gas that pervaded the young cosmos.
These behemoths would have burnt brilliant but brief lives, producing the very first heavy elements.
They would also have "fried" the neutral gas around them - ripping electrons off atoms - to produce the diffuse intergalactic plasma we still detect between nearby stars today.
So, apart from its status as a record-breaker, the newly discovered Hubble galaxy, classified as UDFy-38135539, is of keen interest because it is embedded directly in this time period - the "epoch of re-ionisation", as astronomers call it.
The galaxy was one of several interesting candidates identified in the Hubble Ultra Deep Field (UDF) image of the Fornax Constellation acquired with the telescope's new Wide Field Camera 3 last year.

As a source of light, it barely registers on the Hubble picture which was made from an exposure lasting 48 hours.