Beijing, Aug 31 (IANS) Extra-terrestrial beings do exist but they have not yet come to visit our planet, and the best way to communicate with aliens is to send radio signals, a top Chinese official said Tuesday.

Zhu Jin, curator of the Beijing Planetarium, said aliens are likely to be present on some planets. Since there are about one trillion planets going around fixed stars, the possibility of the earth being the only planet with living creatures was 'too slim to be true', China Daily reported.

But as to reports of sighting of unidentified flying objects (UFOs), Zhu said they cannot be true.

Some UFOs were proved to be planes, kites or other normal objects, and many weird situations can be re-demonstrated and re-created, he said.

Zhu said the distance the Voyager 1 spacecraft has travelled in the past 33 years only accounts for one-thousandth of the solar system's reach. It will take 10,000 years for human beings to visit planets outside the solar system.

So, if aliens living in a faraway planet have a similar level of intelligence as human beings, it was impossible for them to travel to earth, he said.