Fourth 'habitable' planet close to home
Earthly neighbour Astronomers have found the fourth potentially habitable planet outside our solar system with temperatures that could support water and life, only 22 light-years from Earth.
The team analysed data from the European Southern Observatory about a star known as GJ 667C, which is known as an M-class dwarf star and puts out much less heat than our Sun.
However, at least three planets are orbiting close to the star, and one of them appears to be close enough that it likely absorbs about as much incoming light and energy as Earth, has similar surface temperatures and perhaps water.
The new rocky planet, GJ 667Cc, orbits its star every 28.15 days - meaning its year equals about one Earth month - and has a mass at least 4.5 times that of Earth, according to the research published in Astrophysical Journal Letters .
"This means that overall the planet absorbs about the same amount of energy from its star as the Earth absorbs from the Sun. That would give the planet the right temperature, if it has a rocky surface and a wet atmosphere, to host liquid water," says study co-author says Professor Tinney of the University of New South Wales. "And liquid water is seen as an essential pre-condition for the development of life."
The theory about water, however, cannot be confirmed until astronomers learn more about the planet's atmosphere.
Opens up planet forming possibilities
Other planets circling the same star - which is part of a three-star system - could include a gas-giant and an additional super-Earth with an orbital period of 75 days, but more observations are needed to confirm that.
Some experts have been sceptical that M-class dwarf stars could have planets that support life because they are too dim and tend to have lots of solar flare activity which could send off lethal radiation to nearby planets.
And even though this star, GJ 667C, has a much lower abundance of elements heavier than helium, such as iron, carbon, and silicon - the building blocks of terrestrial planets - than our Sun, astronomers are intrigued by the possibilities.
"This discovery shows that habitable planets could form in a greater variety of environments than we previously considered," says Dr Simon O'Toole of the Australian Astronomical Observatory, who was also involved in the study.
French astronomers in May last year confirmed the first exoplanet, Gliese 581d, to meet key requirements for sustaining life. It is a rocky planet about 20 light-years away.
Swiss astronomers reported in August that another planet, HD 85512 b, about 36 light-years away seemed to be in the habitable zone of its star.
The US space agency NASA confirmed its first such planet late last year, Kepler 22b, about 600 light-years away.