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HindustanTimes Sat,23 Aug 2014

Life & Universe

Indian-origin scientist among those who discovered most distant galaxy ever
Agencies
Washington, October 24, 2013
First Published: 15:15 IST(24/10/2013)
Last Updated: 15:22 IST(24/10/2013)

Astronomers have found the most distant galaxy ever, a discovery that pushes back scientists’ view of the universe to about 700 million years after it is thought to have come into existence.

The group of scientists who made the discovery includes one of Indian-origin.

The galaxy is seen as it was when the universe was only about 5% of its current age of 13.8 billion years, researchers said.

The team’s observations showed that the new galaxy, designated as z8_GND_5296, is forming stars extremely rapidly – producing each year about 300 times the mass of our Sun.

By comparison, the Milky Way forms only two to three stars per year.

Researchers identified the very distant galaxy candidate using deep optical and infrared images taken by the Hubble Space Telescope.

Follow-up observations of this galaxy by the Keck Telescope in Hawaii confirmed its distance.

Light from the galaxy took about 13.1 billion years to reach the orbiting Hubble Space Telescope and the Keck Observatory in Hawaii.

The team selected several candidates, based on their colours, from the approximately 100,000 galaxies identified in the Hubble Space Telescope images taken as part of the CANDELS survey, the largest project ever performed by the Hubble.

“What makes this galaxy unique, compared to other such discoveries, is the spectroscopic confirmation of its distance,” said astronomer Bahram Mobasher, University of California, Riverside.

“By observing a galaxy that far back in time, we can study the earliest formation of galaxies. By comparing properties of galaxies at different distances, we can explore the evolution of galaxies throughout the age of the universe.”

By performing spectroscopy, researchers are able to accurately gauge the distances of galaxies by measuring a feature from the ubiquitous element hydrogen called the Lyman alpha transition.

It is detected in most galaxies that are seen from a time more than one billion years from the Big Bang.

Of the 43 galaxies observed, the research team detected the Lyman alpha feature from only z8-GND-5296.

The researchers suspect they may have zeroed in on the era when the universe made its transition from an opaque state in which most of the hydrogen is neutral to a translucent state in which most of the hydrogen is ionised.

“The difficulty of detecting the hydrogen emission line does not mean that the galaxies are absent,” said Naveen Reddy, an assistant professor of astronomy.

“It could be that they are hidden from detection behind a wall of neutral hydrogen.”

The new distance record-holder lies in the same part of the sky as the previous record-holder, which also happens to have a very high rate of star-formation.

The study was published in the journal, Nature.
(Inputs from Reuters & PTI)


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