TV signals 'could point to alien life'

New radio telescopes designed to study the early universe may be able to pick up TV transmissions from alien civilisations, scientists said today.

Aliens within 1,000 light years of Earth could be detected by spotting their leaking television signals, it is claimed.

One of the first of the new-generation telescopes is the Low Frequency Array (LOFAR) being built in the Netherlands.

It is equipped to receive radio waves emitted by hydrogen molecules in the early universe.

Although these signals originally had short wavelengths, the expanding universe has stretched them over time.

Today they have wavelengths of several metres, which means they fall within the range of TV, radio, and military radar transmissions.

“By a happy accident, the telescopes will be sensitive to just the kind of radio emission that our civilisation is leaking into space,” said scientist Dr Abraham Loeb, from Harvard University in the US.

If ET is producing similar signals, these will be visible as “spikes” in the radio spectrum, New Scientist magazine reported.

Dr Seth Shostak, from the SETI (Search for Extra Terrestrial Intelligence) Institute in Mountain View, California, said: “This is radio SETI, but at wavelengths that SETI experiments haven’t probed in the past. That by itself is reason enough to recommend it.”

Leakage of TV signals would do more than tell astronomers that ET watches Alien Neighbours.

It could also provide valuable information about the extraterrestrials’ home planet.

A telescope such as LOFAR would be able to detect the shift in wavelength as an ET planet orbits round its parent star.

It would then be possible to work out the shape of the orbit, the tilt of the planet, and the planet’s distance from the star.

This in turn will allow astronomers to estimate the planet’s surface temperature, indicating whether it has liquid water.

By some estimates there could be as many as 100 million stars with planets within TV range.

But whether aliens are discovered depends crucially on their stage of development. To pick up TV or radio signals from an alien civilisation, it would have to be about as advanced as our own.

Another problem would be filtering out the mass of signals generated from Earth.

“Sorting out ET from the BBC will be a substantial challenge,” said Dr Shostak.