AS astronomers scan the universe for signs of intelligent life, a group of researchers predicts other beings just might be looking at us.

A scientific paper published in this week's online edition of Astrophysical Journal suggests alien astronomers armed with a large space telescope could detect our planet and possibly determine the presence of life.

"They would only be able to see earth as a single pixel, rather than resolving it to take a picture,'' University of Florida astronomer and paper co-author, Professor Eric Ford, said.

"But that could be enough for them to identify our planet as one that likely contains clouds and oceans of liquid water.''

In the past 20 years, astronomers have found more than 200 planets. However, none appear to have the conditions for supporting earth-like life.

Most are hot-gas planets similar to Jupiter, with no solid surface and an atmosphere composed largely of hydrogen and helium.

"The goal of (our) project was to see how much information you can extract from very limited data,'' fellow co-author and MIT associate professor, Sara Seager, said.

According to the paper, a great deal of information about a planet can be gleaned from that single pixel and the way it changes over time.

The paper suggests an alien telescope could collect enough light to identify chemicals in our atmosphere and record periodic changes in the brightness of the earth due to clouds and rotation.
It may even be able to determine the presence of land and oceans from earth's changing light pattern.

Prof Ford believes the hypothetical research will be useful to astronomers designing the next generation of telescopes, providing an outline of the capabilities required for studying earth-like planets.

He hopes that his research will help to motivate an ever larger space telescope that could search for earth-like planets around many stars.

"Maybe somebody's looking at us right now,'' Ms Seager said.