THE SEARCH FOR alien intelligent life has obsessed scientists for centuries – and the search for potentially habitable planets has gone hand-in-hand.
Currently, we has a list of five planets that scientists believe have the potential to harbour life…. (although you might want to wait a little longer before packing your bags).
The confirmation of Kepler 22b’s existence was made in December 2011 to much fanfare. It is the first known transiting planet to orbit within the habitable zone of a Sun-like star, which excited some commentators so much they hailed the planet as “Earth 2.0″.
It’s known that the planet’s radius is roughly 2.4 times that of the Earth but its mass and surface composition remain a mystery. It has been speculated that Kepler 22-b is a watery ‘ocean world’ with a rocky core but (being 600 lights years away from Earth) confirmation of this will be tricky. For a while at least.
Image via NASA: Artist’s conception of Kepler-22b
Gliese 581 g (aka Zarmina’s World)
Gliese 581 g has also been hailed as a potential “second Earth” by some scientists, while others have questioned whether it actually exists.
The team that discovered the planet, which is also known as Zarmina’s World, reported that it had a mass similar to that of Earth and was close to the centre of the habitable zone – leading to hopes that the first potential Earth twin outside the Solar System had been discovered. However, the issue remains controversial.
The nearby star, Gliese 581, is orbited by four planets – the outermost planet, Gliese 581d, is also suspected of being habitable and, interestingly, it’s the only known case of potential habitable exoplanets orbiting the same star.
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Gliese 667 Cc
The planet is a member of a triple star system in the Scorpius constellation. It’s believed to be at the centre of the habitable zone and receives only 10 per cent less stellar energy than that which the Earth receives from the Sun.
The proposed location of Gliese 667 Cc would mean it could have liquid water – an essential component of life as we know it.
HD 85512 b
HD 85512 b is an extrasolar planet orbiting Gliese 370 star, about 36 light-years from Earth. Is one of the smallest exoplanets discovered to be on the edge of the habitable zone and considered to be one of the best candidates for habitability.
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Gliese 581d is another exoplanet orbiting the red dwarf star Gliese 581. It was initially thought to be too cold for life, with the closer-in planet Gliese 581c deemed more likely to be habitable. However, atmospheric experts later discovered that if the planet had liquid oceans like Earth, they would rapidly evaporate in a ‘runaway greenhouse’ effect similar to that which gave Venus the hot, inhospitable climate it has today.
Image via Wikicommons
The top 5…
Image via the Planetary Habitability Laboratory