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Sci-Tech

Big discoveries heralded by a faint breath of hydrogen from a distant galaxy

The Square Kilometre Array had detected a tiny signature from 5 billion light years away that heralds great finds in the future.

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The Australian Square Kilometre Array Pathfinder in Western Australia. Commonwealth Scientific and Industrial Research Organisation

One of the most significant finds of the Australian Square Kilometre Array Pathfinder may seem tiny, but it signals much bigger things ahead.

Leading a team of researchers, James Allison of the Commonwealth Scientific and Industrial Research Organisation used the radio telescope array to detect a very faint radio signal from galaxy PKS B1740-517, located 5 billion light-years away in the constellation of Ara.

The radio signal carried the "imprint" of cold hydrogen gas after passing through the element between its source galaxy and Earth. The gas absorbed some of the signal as it passed through, causing a small dip in the signal received by Allison and his team.

It's not unexpected or unusual information, but the fact that it was detected at all spells great discoveries in the ASKAP's future because hydrogen, while plentiful in the universe, is the stuff from which new stars are born.

"This catch shows we're going to bag a big haul of galaxies," Allison said in a statement.

This is partially because of ASKAP's size -- with 36 antennas, it's one of the largest radio telescope arrays in the world -- and partially because of its location. The radio telescope array, which officially launched in late 2012, is part of the Murchison Radio-astronomy Observatory near Murchison, Western Australia, a remote region with a very low population density.

This remoteness -- and relative lack of human population -- means very low radio interference, which means in turn that the cold hydrogen signature was very easy to spot in the ASKAP data.

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The dip in the signal caused by the cold hydrogen, clearly visible in the data. CSIRO

"At many observatories, this dip would have been hidden by background radio noise, but our site is so radio quiet it stood out clearly," Allison said.

Allison and Elaine Sadler, an astrophysics professor of the University of Sydney, will conduct ongoing research that uses this absorption technique to find galaxies up to 10 billion light-years away to gauge how much cold hydrogen they contain.

"ASKAP looks at a relatively unexplored part of the radio spectrum, 700 to 1,800 megahertz," Sadler said in a statement. "This means we'll be able to detect hydrogen gas deeper in space and, thanks to ASKAP's wide field of view, also over a much larger volume than we could before. We'll be hunting for galaxies that are 5 to 8 billion years old, a time span that represents a fifth of the universe's history."

That time span is of particular interest because star birth rates were a lot higher 10 billion years ago than they are now. By focusing their efforts on the period between 5 and 8 billion years ago, the team hopes to gain an understanding of why those rates dropped.

Allison presented the findings today at the National Astronomy Meeting in the UK. "These latest research findings are demonstrating that ASKAP can do what other telescopes can't," he said.