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...meanwhile, elsewhere in the universe.

HABITABLE "super-Earths" with up to five times the mass of our own planet could possess vast, long-lasting oceans, new research suggests.

Oceans cover more than two thirds of the Earth's surface and are continually replenished by volcanic activity dragging up water buried deep underground.

But a new study indicates that "habitable zone" planets with two to four times the Earth's mass may be even better at establishing and maintaining oceans.

Most scientists agree that liquid water is a prerequisite for the development of life as we know it.

Meanwile, eight more planets have been discovered that could possess watery oceans and life, including two of the most Earth-like yet found.

The new worlds double the number of small exo-planets believed to be circling their stars in the "habitable zone" - the narrow region in which temperatures are mild enough to allow liquid surface water.

By "small" astronomers mean planets with less than twice the Earth's diameter.

"Most of these planets have a good chance of being rocky, like Earth," said lead scientist Dr Guillermo Torres, from the Harvard-Smithsonian Centre for Astrophysics in Cambridge, US.

The two most Earth-like planets, known as Kepler-438b and Kepler-442b, both orbit red dwarf stars that are smaller and cooler than the Sun.

With a diameter just 12% bigger than Earth, Kepler-438b has a 70% chance of being rocky, the scientists have calculated. Kepler-442b is about one-third larger than Earth, and the likelihood of it being rocky is around 60%.

To be in the habitable zone, also known as the "Goldilocks zone", a planet must be not too hot or too cold and receive roughly as much sunlight as Earth. Too much heat from its star, and any water would boil away as steam. Too little, and the water would freeze solid. "For our calculations we chose to adopt the broadest possible limits that can plausibly lead to suitable conditions for life," Dr Torres added.

Kepler-438b receives about 40% more light than the Earth giving it a 70% probability of having a habitable zone orbit. In comparison, baking hot Venus has twice as much.

The other gets about two-thirds as much light as Earth and is 97% likely to be in the habitable zone.

Co-author Dr David Kipping, also from the Centre for Astrophysics, said:"We don't know for sure whether any of the planets in our sample are truly habitable. All we can say is that they're promising candidates."

Neither of the planets are our close neighbours. Kepler-438b is located 470 light-years from Earth while the more distant Kepler-442b is 1,100 light-years away.

All the planets were too small to confirm by measuring their masses. Instead, they were validated using a computer program that determined they were statistically likely to be planets.

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An artist's impression of an Earth-like planet orbiting a star near the |end of its life

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Title Annotation:Features
Publication:Evening Chronicle (Newcastle, England)
Date:Jan 8, 2015
Words:475
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