Long-distance sighting

With astronomers getting a glimpse of the most distant galaxy, a door to gaining precious new knowledge about the crucial evolutionary stages of the universe has been opened.

The newly discovered galaxy designated ms 1512-cB58 has a redshift of 6.56, which means it is about 14 billion light years away from the Earth. It belongs to a time when the universe was only about 780 million years old. This is about 50 million years earlier than the appearance of the most remote quasar -- a superbright object powered by black holes -- yet observed whose redshift was 6.28. The galaxy presents the oldest pictures astronomers have of the universe. Says University of Hawaii professor Esther Hu, "This galaxy is forming stars at a time speculated to be in the so-called Dark Ages of the universe, when galaxies began to turn on."

To espy faint galaxies so far away, astronomers had to use gravitational lens, a massive cluster of galaxies that bends and amplifies light from more distant objects behind and peers into the depths of the universe. The researchers aimed one of the 10-metre Keck I and Subaru telescopes at the galaxy cluster, Abell 370 in this case. Abell 370 magnified light from a galaxy behind it that is 14 billion light years away. Even with the gravitational lensing help, the scientists were not able to view the galaxy in visible light but did manage to spot the signature of Lyman alpha hydrogen emission, which blazes during star formation. "If a few galaxies had 'turned on' by this point the emission would have been smothered by the surrounding hydrogen gas and the light would never have made it out to us," explains graduate student and team member of University of Hawaii Peter Capak. Being able to see the Lyman alpha line from such a remote galaxy means that the "fog" had already begun to lift by this early era and the universe's dark period ended sooner than astronomers thought. Another team member, Richard McMohan of Cambridge University, says the galaxy is "probably about half the size of our own Milky Way".

While McMohan hopes that new technology will soon allow astronomers to see even more distant galaxies that pioneered star formation 14 billion years ago, Hu says that the next big step in finding earlier galaxies will be to use space-based observatories. The Next Generation Space Telescope is scheduled to be launched in 2009. Once outside the shroud of the atmosphere, the us $500 million telescope is likely to reveal the universe's most ancient galaxies and the secrets they hold.

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