For the first time, a group led by astronomer Professor Steven Tingay from Curtin University have used a sensitive type of radio telescope, known as a very long baseline interferometer, to listen out for radio signals coming from a distant planet.
For eight hours in June 2007, they trained one of these interferometers – the Australian Long Baseline Array – toward a nearby star known as Gliese 581, which is thought to have two potentially life-sustaining planets orbiting it.
Despite the fact that the foray drew a blank, the researchers say their approach holds guarantee for the future. Their report, posted on the pre-press internet site arXiv.org, is due to be published in The Astronomical Journal.
“We’ve proved the concept,” says Tingay. “Although it’s a null result, it’s good to be able to show that the technique works.”
Quite prolonged baseline interferometers are well suited to the search for radio signals from space due to the fact they are made up of numerous telescopes separated by large distances. The three Australian Prolonged Baseline Array dishes utilised in this instance have been spread all around NSW.
“One of the problems with the search for extraterrestrial intelligence is that if a telescope picks up a narrow band radio signal, ultimately you don’t know if it’s coming from a distant planet, or the TV antenna 20 kilometres away,” explains Tingay.
The benefit of interferometers such as the ALBA – or the upcoming Square Kilometre Array – is that any human interference probable would be confined to one or two of these antennas, he says.
“Even if you did see it on far more, you could quite speedily get rid of it as coming from the part of the sky wherever the planet is.”
Proof of concept
Tingay and colleagues, such as PhD student Hayden Rampadarath, targeted their search on a modest portion of the radio frequency spectrum – from 1230 to 1544 MHz.
“That is the region of spectrum that consists of the hydrogen line emission, which people feel is a reasonable place to look,” says Tingay. “But it is a tiny, tiny slither of the radio frequency.”
The astronomers detected 222 potential alien signals for the duration of their observation. Even so they were in a position to rule out all of these utilizing automated analysis tactics.
Still, the negative finding does not definitively show there are no alien civilisations orbiting Gliese 581, notes Tingay.
What it does imply is that during the period they had been observing, there were no strong radio signals directed from that planetary system toward Earth.
“We would have observed a signal brighter than 7 megawatts per hertz, but that is a rather strong signal,” he says. “Who knows, maybe it was a public holiday on that planet or a thing and we missed out.”
The findings also show that the Square Kilometre Array would be a excellent addition to the hunt for alien intelligence, he notes.
“The genuine value of this is in displaying the approach functions and you could feasibly run this kind of program on the SKA for almost zero cost.
Sources and more information:
• First VLBI SETI Search Finds No Radio Transmissions From Gliese 581