Six of the Square Kilometre Array Pathfinder project’s 36 dishes, situated 300km inland from Geraldton, have picked up a wisp of cosmic radio waves coming from the galaxy PKS B1740-517 in the direction of the southern constellation of Ara.

The discovery has astronomers salivating because the five-billion-year-old signal shows ASKAP will be able to detect galaxies other telescopes can’t.

The signal carries the ’imprint’ of cold hydrogen gas - the raw material for forming stars and plentiful in most galaxies - that it passed through on its way here. Astronomers can detect a galaxy from its hydrogen gas even when its starlight is faint or hidden by dust.

Although tiny, the signal stood out clearly in the ASKAP data.

‘‘This catch shows we’re going to bag a big haul of galaxies,’’ research leader James Allison of the CSIRO said.

While many radio telescopes are bedevilled by radio interference - unwanted signals that clutter up the spectrum - the ASKAP site is exquisitely radio quiet.

ASKAP also gives astronomers a very large ’net’ with which to trawl for signals, a 300 MHz wide chunk of radio spectrum to search through.

‘‘That’s more than most telescopes have, and it gives us a better chance of finding something new,’’ Dr Allison said.

Elaine Sadler, Professor of Astrophysics at the University of Sydney and a member of the research team, plans a large ASKAP survey aimed at detecting several hundred galaxies.

‘‘ASKAP looks at a relatively unexplored part of the radio spectrum, 700 to 1800 megahertz,’’ Professor Sadler said.

‘‘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 five to eight billion years old, a timespan that represents a fifth of the universe’s history.’’

Ten billion years ago, galaxies were making stars 10 times faster than they do now. By studying galaxies five to eight billion years old, astronomers hope to understand why the rate dropped.

‘‘We want to learn how much hydrogen galaxies had in this period for forming stars,’’ Professor Sadler said.

‘‘Until now we’ve had few tools for doing that.’’

The Square Kilometre Array will be 50 times as sensitive as the best existing radio telescopes, consisting of thousands of linked antennas spanning WA and South Africa.

AAP