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Giant telescope could eavesdrop on alien TV

If this succeeds, it might be possible as a next step to decode the signals and watch them on our own TVs, according to one astronomer.

The planned telescope, called the Square Kilometer Array (SKA), “could potentially end our cosmic isolation and help us understand how we got here,” wrote the astrononomer, Jill C. Tarter, in a paper in the December issue of the research journal New Astronomy Reviews.

Telescopes designed to detect hoped-for signals from extraterrestrial life already exist. But they’re considered powerful enough only to detect signals from beings who are purposely trying to send the signals across space. This makes it unlikely we would find any civilizations that, like ours, aren’t attempting this feat.

We do, however, watch TV and listen to radio. These activities leak signals into space that could theoretically reveal our presence to aliens. 

SKA will be designed to detect these types of signals from the aliens themselves, if they’re close enough. It could also detect radar possibly being used by aliens, scientists say. Radar signals are pulses of radiation sent out in order to locate distant objects such as airplanes.

SKA could probably detect TV signals from planets around the four closest stars to the Sun, according to an estimate by Tarter, who is director of research for the Search for Extraterrestrial Intelligence (SETI) Institute in Mountainview, California. 

While this is a small number, SKA’s range for detecting radar would be far greater. If aliens are using telescopes with powerful radar, as some of ours do, SKA might be able to detect this out to a distance that includes about 60 billion nearby stars, Tarter estimated. This number shrinks to about 500 stars for detecting radar signals like those used at airports, which are weaker.

The journal issue containing Tarter’s paper also includes a set of other scientific papers outlining the scientific goals of SKA, a $1 billion project. An international consortium of 15 countries, including Australia, China, India, the United States and 10 European countries, has been planning SKA for a decade. The participants plan to pick a site for the telescope in 2006 and start construction in 2012. 

It might seem surprising that a telescope could pick up TV signals. It could because such transmissions are made of light, just like starlight – except their light is invisible to the eye, which can detect only light waves within a specific range of sizes.

SKA would have one square kilometer (247 acres) of area for detecting transmitted light. This is 30 times as much as the biggest existing telescopes.

The types of waves used for TV and radio are about a million times longer, from crest to crest, than those used for visible light. This “long-wavelength” light requires a correspondingly larger type of telescope to detect, called a radio telescope. 

But radio telescopes are easier to build in some respects than regular, optical ones: they don’t need smooth, mirrored surfaces to collect light. This is because long-wavelength light is less scrambled by surface bumps of any given size than short-wavelength light.

Another peculiarity of a radio telescope is that it often consists of an array of smaller telescopes, or reflectors that look like satellite dishes. This is one possible design for the SKA, according to researchers.

How would SKA scientists recognize television transmissions, or other signals from intelligent beings, if they were found? 

Although there is no definite agreement on this, astronomers say one way is simply to look for signals of a type that stars and other known celestial sources physically can’t produce. Another is to analyze the light waves for patterns, which might indicate an intelligent being is producing them. One such pattern might consist of two transmissions at different wavelengths, carrying identical signals.

Does this mean we could we watch alien TV?

Maybe, Tarter said, but although SKA could detect “leaked” signals, it probably won’t be sensitive enough to decode them to put them on our televisions. But a future telescope could do so, she added. Once SKA made the initial detection “there would probably be enough excitement and funding to allow you to build a large enough telescope” for decoding, she speculated.

Not that the information we got would be up to date. 

If we could watch alien TV shows based on information gleaned from SKA, they would be between four and six years old, at least. This is how long it takes for light from the four closest stars to get to Earth. The time discrepancy could be bigger for the other types of transmissions, such as various types of radar. For telescope radars similar to our most powerful one, this could be as high as about 50,000 years, corresponding to a distance about halfway across our galaxy.

But SKA could do far more than pick up transmissions from intelligent beings, scientists say: it also will peer at the most distant reaches of the universe with unprecedented accuracy in the longer wavelengths, allowing it to study the origins of the earliest galaxies ever formed.

It will also examine the formation of planetary systems to determine how life may evolve, according to researchers. 

Scientists have already detected, floating among the stars, organic molecules crucial for life. The SKA could help answer whether these same molecules make it onto forming planets to spark the process of life. It could do so by scouring planetary systems in every stage of development to find out whether these organic molecules leave characteristic marks in the light that reaches us.

SKA would produce “movies showing a (small) fraction of the formation process of a terrestrial planet,” wrote Joseph Lazio of the Naval Research Laboratory, Washington, D.C., and colleagues in another paper in the same issue of the journal. 

“Combined with other bioastronomical facilities, on the ground, in space, and on other planets in the solar system, the SKA will play a key role in finding life elsewhere in the Universe,” Lazio and colleagues wrote.

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