Australia's role in the search for life in space
Australia is playing a key role in the world's biggest search for extra-terrestrial intelligence.
An Australian radio telescope in operation for more than 50 years will be one of the primary instruments used in a new $100m (A$137m; £64m) search for life elsewhere in space.
The 10-year project - known as the Search for Extra-Terrestrial Intelligence (SETI) - was announced this week by Prof Stephen Hawking in London, and is being funded by Russian billionaire and venture capitalist Yuri Milner.
One of the two main radio telescopes being used in the search is a 64-metre-wide parabolic dish known as the Parkes telescope.
The facility, 380km (236 miles) west of Sydney, belongs to Australia's national science organisation, the Commonwealth Scientific and Industrial Research Organisation (CSIRO).
A multi-million dollar agreement has been worked out that will give project scientists access to 25% of the telescope's time over the next five years, says Lewis Ball, chief of CSIRO's Astronomy and Space Science unit.
Mr Ball says its location will allow the project to survey the centre of the Milky Way galaxy, which passes almost directly overhead in the southern sky.
"That's the region of our galaxy that has the highest concentration of stars, and therefore planets… that may support life," he says.
"It's the richest area of our galaxy to search for extraterrestrial intelligence and it's right on our doorstep."
Faint radio signals
Operating since 1961, the Parkes telescope played an important role in televising the Apollo 11 moon landing.
Its main purpose, however, is astronomy, and numerous upgrades over the past five decades have kept it at the cutting-edge.
"The Parkes telescope is one of the largest, fully steerable telescopes in the world," says Prof Matthew Bailes, an astronomer at Swinburne University of Technology, and the leader of the Australian team taking part in the project.
It has been particularly good at detecting very faint radio signals from small, rapidly spinning stars in our far-flung galaxy known as pulsars, identifying more than half of the 2,500 known, he says.
This track record makes it an ideal instrument for SETI as the "signal processing required to find a pulsar is very similar to what you have to do for aliens," he says.
'No manual for finding aliens'
Radio telescopes are designed to receive radio waves from sources in outer space such as pulsars, or possibly, alien civilisations.
The curved dish, or antenna, redirects the signal to a central receiver. The radio waves are then converted into a digital signal and passed to a computer network for analysis - either in real-time, or down the track.
The new project will survey the one million closest stars to Earth and will scan five times more of the radio spectrum than the next best SETI programme.
But characterising an alien signal is a daunting challenge, says Prof Bailes.
"Unfortunately there's no manual for how to find aliens."
When you know what you're looking for "it's very easy to know the exact pattern recognition algorithms you need to run", he says.
"It's much harder to find something when you're not even sure what it is. There's going to have to be several hypotheses, and it might be quite easy to get them wrong, and to just let these radio waves from aliens wash past us."
The other major challenges are processing the enormous amounts of data the search will yield - close to 30 gigabytes, or a Blu-ray DVD, every second - and dealing with radio frequency interference, which becomes more problematic as you try to detect signals across a broader range of the spectrum.
"Our [potential] alien transmissions are going to be competing with your mobile handset for our attention, and it would be a tragedy if all we end up listening to are people's Facebook transmissions," says Prof Bailes.
To get around this problem, he and other project scientists at the CSIRO and the University of California, Berkeley in the US, are planning on developing new technologies to capture and process the data, and to hopefully eliminate human-generated interference.
He anticipates that the team will also build new processors that are able to make one-million-billion calculations per second - handling what is known as a petaflop of data.
Currently, their most advanced processors can handle a quarter of that, says Prof Bailes.
"These will be very pioneering, and will have applications beyond alien hunting," he says.
And while the chances of making contact are "tiny", he says if it happens it will be "incredibly significant".
"It's a high-risk, high-reward endeavour but I'm old enough to have some fun," he says.
Myles Gough is a science writer based in Sydney.