Thursday, September 30, 2010

Newly discovered extra-solar planet may support life

Gliese 581 is a red dwarf star located 20.3 light years away from Earth in the constellation Libra. Its estimated mass is about a third of that of the Sun,

Sol compared to Gliese 581
Observations suggest that the star has at least six planets: Gliese 581 e, b, c, g, d, f. Significantly, planet g is thought to be close to the middle of the star's habitable zone, although it is expected to be tidally locked with one side of the planet always facing the red dwarf.

Astronomers have discovered the first planet outside the solar system with the potential to support life. On 29 September 2010, astronomers at Keck Observatory announced the discovery of Gliese 581 f and Gliese 581 g, both in nearly circular orbits. Gliese 581 g has a mass of 3 to 4 earth-masses, with an orbital period of 37 days, and is at a distance from Gliese 581 that is well within the star's habitable zone.

The planet is predicted to be tidally locked, with one side of the planet always facing the star.

The Gliese 581 solar system would  be very different from the Earth's

US-based scientists found the planet using precise measurements from the Keck telescope in Hawaii, which has been scrutinising Gliese 581 for more than a decade.

The new planet, called Gliese 581g, is one of several known to be orbiting the star, but is the first to be discovered in the so-called Goldilocks Zone, where the distance from the star means that temperatures are neither too hot or too cold for life to exist.

"We had planets on both sides of the habitable zone - one too hot and one too cold - and now we have one in the middle that's just right," Steven Vogt of the University of California, who worked on the team that discovered the planet, said.

Less than 500 planets have been discovered outside of the solar system, and the fact that this one lies in the middle of the Goldilocks Zone suggests that habitable planets could be extremely common.

Relative term

"Nearby" is a relative term in astronomy, where the distances between stars and galaxies are enormous. A light-year is the distance light can travel in one year at a speed of 300,000km a second, or about 10 trillion km. Lying 20 light years from Earth, Gliese 581 is at least 200 trillion km away.

At that distance, it is impossible to make direct observations of planets. Instead, astronomers observe tiny "wobbles" in the star they orbit caused by the gravitational pull of orbiting planets.

The latest discovery has average temperatures averaging from -31 to -12 degrees Celsius. Because the planet does not rotate, one side of it is locked in perpetual darkness and is extremely cold, while the other is always facing its star and is much hotter. The habitable parts of planet are thought to be in the "dusk" areas, where the star would appear low in the sky.

Scientists say if the planet was rocky, like Earth, its gravity would be similar. The temperature would also theoretically allow liquid water to exist on its surface, but the team say they have not detected any evidence of water so far. 

This planet would very alien to humans. The light spectrum would be redder and the weather would be unpredictable if the planet is tidally locked. The planet would need water to habitable.

In October 2008, members of the networking website Bebo beamed A Message From Earth, a high-power transmission at Gliese 581 c, using the RT-70 radio telescope belonging to the National Space Agency of Ukraine.

This transmission is due to arrive in the Gliese 581 system's vicinity by the year 2029; the earliest possible arrival for a response, should there be one, would be in 2049.

sources: Gliese 581 - Wikipedia, the free encyclopedia and Al Jazeera

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