Evidence of water has been detected for the first time in a planet outside our solar system, an astronomer said on Tuesday, a tantalizing find for scientists eager to know whether life exists beyond Earth.

An illustration of a Jupiter-like gaseous planet located 150 light years from Earth. Evidence of water has been detected for the first time in a planet outside our solar system, an astronomer said on Tuesday. [Reuters]

Travis Barman, an astronomer at Lowell Observatory in Flagstaff, Arizona, said water vapor has been found in the atmosphere of a large, Jupiter-like gaseous planet located 150 light years from Earth in the constellation Pegasus. The planet is known as HD 209458b.

Other scientists reported in February that they were unable to find evidence of water in this planet's atmosphere, as well as another Jupiter-like planet.

"I'm very confident," Barman said in an interview. "It's definitely good news because water has been predicted to be present in the atmosphere of this planet and many of the other ones for some time."

Lowell Observatory, a privately owned astronomical research institution, announced the finding, which has been accepted for publication in the Astrophysical Journal. The research was backed by NASA, it said.

The detection of the presence of water vapor was possible because this planet, from the vantage point of Earth, orbits directly in front of its star every 3-1/2 days, allowing crucial measurements to be made. It is what is known as a transiting planet.

Scientists searching for signs of life beyond Earth are keen to learn about the presence of water on other planets -- both in and beyond our solar system -- because water is thought to be fundamental to the existence of life.

Barman noted that a Jupiter-like gaseous planet such as this one, as opposed to a rocky one like Earth, is highly unlikely to harbor life, and said the finding about water vapor in its atmosphere does not answer one way or another questions about the existence of extraterrestrial life.

'PART OF PUZZLE'

The findings, he said, "are not adequate to really address a question as deep and profound as the existence of life elsewhere. We're not there yet."

"Certainly this is part of that puzzle -- understanding the distribution of water in other solar systems is important for understanding whether or not conditions for life are possible. The presence of water does not exclude the possibility of life, but it doesn't mean it's there, either," Barman added.

He said his findings do provide good reason to believe other planets beyond our solar system also have water vapor in their atmospheres.

The conclusions stemmed from an analysis of Hubble Space Telescope measurements by Harvard University's Heather Knutson and new theoretical models developed by Barman, Lowell Observatory said.

Water is plentiful on Earth and has been found elsewhere in our solar system, for example in large deposits of ice at the north and south poles of Mars.

Planet HD 209458b also was the first planet outside the solar system found with an atmosphere and the first detected transiting planet. There are more than 200 known planets outside our solar system.