科学家继续努力寻找外星智能生物

After the 1982 megahit E.T. the Extraterrestrial, the search for alien intelligent life was much in focus. And although no evidence has yet been found, scientists are still watching and listening to deep space. Now, recent technological advances are giving them additional hope.

The search for extraterrestrials is being done with telescopic "eyes" and "ears".

Michael Liu, an astronomy professor at the University of Hawaii, in Honolulu, uses an optical telescope to look for planets orbiting distant stars.

Liu says until recently, earth-bound telescopes could not provide extremely sharp images of distant stars because of the refraction of light passing through earth's atmosphere. But that has changed.

"One of the technological advances that has happened in the last 15 years is that telescopes are now equipped with technology known as adaptive optics, that essentially allows you a way to measure in real time the trembling of the earth’s atmosphere and correct for those images," Liu said.

Liu says the images of stars are now more than 10 times sharper than before.

Scientists can not actually see distant planets. Instead they calculate their presence by measuring their gravitational pull at their stars. It is also possible to detect heat emitted by very young planets that provides clues to their physical properties, like how big they are, how much energy they put out, even the materials they are made of.

"Every piece of evidence we’ve found today suggest that planetary systems, planets around the stars, are common," said astronomer Liu. "And we’re getting ever and ever closer -- not quite yet, but we’re getting very close to finding planets just like our earth, around stars just like our sun. And that almost seems inevitable.

Other scientists are using radio telescopes -- huge dish antennas or antenna arrays -- listening to radio emissions from deep space.

Dr. Alan Penny, an astronomy professor at the University of St. Andrews, Scotland, is chairman of the United Kingdom's Search for Extraterrestrials group (UKSETI), which plans to connect all radio telescopes in Britain into a huge network in search of intelligent alien life.

Penny says noise and natural signals from stars and quasars are chaotic, while signals from intelligent life must have a structure.

"There’s no natural source, there’s no star or quasar that can do it. So when you take your picture of the sky and you look at the colors, the equivalent of the colors, if there is one sharp band -- that must be artificial, which means it must be intelligence.

But the sky is enormous. Where exactly will the astronomers look for extraterrestrial life?

Perhaps they’re like us and they live on other planets and they emit strong radio waves, then you point your telescopes at nearby stars which you know have planets, and just within the last 10 years we’ve been detecting planets around nearby stars," Penny said.

Penny says funding for the search will be provided by private grants and he expects the UKSETI network to be fully operational in about two years. In the meantime, other scientists keep looking for extraterrestrial life because, they say, the chances are high that we are not alone.