Astronomers find oldest galaxy yet

WASHINGTON (Reuters) - Astronomers have spotted the oldest galaxy ever seen, one born just 600 million years after the Big Bang.

Their report, published in the journal Nature on Wednesday, confirms that the distant smudge first spotted by the orbiting Hubble Space Telescope is the farthest and thus oldest object ever imaged.

The galaxy has the unglamorous name of UDFy-38135539, the team of European researchers said.

"Here we report the detection of ... photons emitted less than 600 million years after the Big Bang," they wrote.

Light travels at a speed of 186,000 miles a second, or about 6 trillion miles (10 trillion km) a year. Astronomers can use light-speed as a kind of time machine, and seeing light emitted from objects very far away shows them as they were in the past.

In this case, the galaxy's light first started traveling 13 billion years ago, right after the Big Bang.

The distance is measured using what is called red shift, a kind of Doppler effect of light. Just as a train's whistle seems to change in pitch as the train approaches and passes, light's color also shifts.

This galaxy has a red shift of 8.55, making it the farthest and oldest ever seen.

At this time in the early universe, a haze of hydrogen gas was everywhere, but radiation from primeval galaxies was causing a process called ionization that changed the nature of the hydrogen.

The report "represents a fundamental leap forward in observational cosmology", Michele Trenti of the University of Colorado, Boulder, wrote in a commentary.

(Reporting by Maggie Fox, Editing by Julie Steenhuysen and Jerry Norton)