The Pope's chief astronomer has conceded other intelligent beings could exist in outer space.

The conclusion has been drawn by scientific experts called in by the Vatican to study the possibility of extraterrestrial life and its implications for the Church.

It has been four centuries since the Catholic Church locked up Galileo for challenging the belief that the Earth was at the centre of the universe.

The Vatican's five-day conference attracted 30 astronomers, physicists and biologists, including non-Catholics.

It was led by Jesuit priest Father Jose Gabriel Funes, an astronomer and director of the Vatican Observatory.

Father Funes says the possibility of alien life raises "many philosophical and theological implications" but that the gathering was mainly focused on the scientific perspective.

One of the organisers was Chris Impey, a professor of astronomy at the University of Arizona.

He says the aim was to assess the most recent research in the burgeoning field of astrobiology - the study of life in the universe.

"And also getting a sense of when you know the vital breakthrough is going to be made, which is the discovery of life elsewhere," he said.

"Because even though we're looking hard we still only know one planet anywhere with life and that's this one."

Breakthrough coming soon

He says that major breakthrough may be just around the corner.

"If you were going to take a set of bets of the 30 scientists gathered for that meeting, I think most of them would have said on about a time scale of 10 years maybe," he said.

That's a guess from the scientists involved and it could come from either of two directions - it could come from a planetary mission within the solar system that looks at one of the most hospitable places for life nearby which is probably Titan, Europa or Mars.

"Or it could come from telescopic observations of planets that we're finding in increasing numbers around distant stars."

But before one starts looking at the concept through Hollywood eyes, professor Impey has another observation.

"I think there's a big distinction between the finding of microbial life, bacteria or something like that which is actually the most likely form of life to discover initially, and intelligent life - sentient beings with technology, and that's a different strategy," he said.

"So I think on the former, on microbial life it's not likely to challenge the world's major religions - but if we find creatures that rival us or exceed us in intelligence, then I think that's going to be very interesting."

Church's positive response

But perhaps not too interesting, according to Dr Paul Collins, a former priest and now Church historian and Catholic commentator.

He says a belief in extraterrestrial life does not necessarily contradict any basic tenets of the Catholic religion.

"I would think that our response would be a positive one," he said.

"I'm not infallible on this of course, but the reality is that I don't think it does contradict anything within Catholicism.

"Essentially what the Christian faith generally is saying and certainly Catholicism specifically is saying is that God is the ultimate source of life, the ultimate source of reality."

The views of the Catholic Church have shifted radically since the Italian philosopher Giordano Bruno was burned at the stake as a heretic in 1600 for speculating other worlds could be inhabited.

The Vatican Observatory has been at the forefront of efforts to bridge the gap between religion and science and today senior clergy openly endorse scientific ideas such as the big bang theory and evolution.

And Dr Collins sees no problem with where aliens might fit in with the belief that man was created in God's image.

"Every creature reflects the goodness and the creativity of God. Humankind, we certainly would argue that we represent that most fully and most completely," he said.

"But all of creation represents God's creativity. So any extraterrestrial being would certainly represent that creativity as well and may be or may not be more developed than we are."