Water has been discovered on a planet beyond our solar system for the first time, enhancing the prospect that life could be found elsewhere in the Universe.

Observations with the orbiting Spitzer space telescope allowed astronomers to detected water vapour in the atmosphere of a gas giant 64 light years away from Earth, an international team led by a British university reported yesterday.

The planet has the unromantic name HD 189733b and orbits a star in the constellation of Vulpecula, the Fox. Although the Jupiter-like planet on which water has been identified is not likely to be habitable – it is composed chiefly of gas and it is so close to its parent star that parts of its atmosphere are as hot as 2,000C (3,630F) – the discovery suggests that water may be a common presence on planets throughout the galaxy.

The same techniques that were used to pick up the signature of water could also be used to examine more promising homes for life, particularly on smaller, rocky, Earth-like worlds once more powerful telescopes are able to find them.

Giovanna Tinetti, of University College London, who led the research group, said: “Although HD 189733b is far from being habitable, and actually provides a rather hostile environment, our discovery shows that water might be more common out there than previously thought, and our method can be used in the future to study more life-friendly environments.” The discovery, details of which are published in the journal Nature, moved astronomers closer to their goal of finding a watery world that could support life, she said. “The holy grail for today’s planet-hunters is to find an Earth-like planet that also has water in its atmosphere.”

Keith Mason, chief executive of the Science and Technology Facilities Council, which helped to fund the research, said: “This first conclusive evidence of the presence of water vapour in the atmosphere of a planet beyond our solar system provides an exciting breakthrough in our knowledge of extra-solar planets. It represents a real step forward into establishing whether we are alone in the Universe.”

Astronomers are inviting members of the public to contribute to a census of a million galaxies. Visitors to www.galaxyzoo.org will be invited to view stunning images of galaxies, many of which have never been seen before, and to help to sort them into spiral galaxies like our own Milky Way or elliptical galaxies.

Kevin Schawinski, of Oxford University, who is leading the project, said that even untrained observers would be able to help. “It’s not just for fun,” he said. “The human brain is actually better than a computer at pattern recognition tasks like this. Whether you spend five minutes, fifteen minutes or five hours using the site, your contribution will be invaluable.”

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