Washington: Scientists have suggested that the newly discovered planet Corot-9b is temperate enough to allow the presence of liquid water.
Corot-9b was found on 16 May 2008 and orbits its star every 95.274 days, a little longer than Mercury takes to go round the Sun.
It is the first transiting planet to have both a longer period and a near-circular orbit.
A transit is a kind of eclipse and occurs when a celestial body passes in front of its host star and blocks some but not all of the star’s light.
Corot-9b’s orbit is slightly elliptical but at closest approach to its parent star it reaches a distance of 54 million kilometers.
Although that is only about the distance of Mercury in our Solar System, it is by far the largest orbit of any transiting planet found so far.
Because it orbits a star cooler than our Sun, calculations estimate that Corot-9b’s temperature could lie somewhere between -23 degrees C and 157 degrees C.
Corot-9b has a radius around 1.05 times that of Jupiter but only 84 percent of the mass. This leads to a density of 0.90 g/cc, or 68 percent that of Jupiter.
“Corot-9b is the first exoplanet that is definitely similar to a planet in our Solar System,” said Hans Deeg, a researcher at the Instituto de Astrofisica de Canarias.
The similarity is caused by the fact that Corot-9b is sufficiently far from its star to prevent tidal forces from heating its interior.
Tidal forces are created by the strength of gravity weakening from the front to back of the celestial body.
When the difference between the near side and the far side is great, the tidal force can prevent the planet from spinning quickly, forcing it to only show one face to the star.
It can also provide heat to the interior of the planet, changing its physical condition.
Based on calculations, neither of these is possible in this case.
“Although we don’t know, because we can’t see the planet directly, there is reason to believe that this planet has a normal day-night cycle,” said Malcolm Fridlund, ESA Project Scientist for Corot.
It means that lacking a tidal heat source, Corot-9b’s interior is likely to have remained similar to the gas giants in our Solar System.