Let鈥檚 have a sniff. Three exoplanets, similar in size and temperature to our own, are in orbit around an ultra-cool dwarf star. In the future, we could analyse their atmospheres for signs of life.
A team led by Micha毛l Gillon from the University of Li猫ge, Belgium, found the trio by using the Chilean-based TRAPPIST telescope to monitor the drop in brightness as the planets passed in front of their star. Two of them are at the inner edge of the habitable zone 鈥� the region around the star that allows liquid water to exist 鈥� and one is in or beyond it.
Although the exact mass of the triplets isn鈥檛 known, the team estimate these planets must be between 50 per cent and twice Earth鈥檚 mass. They are probably made of rocks and maybe ice, making them similar in composition to the solar system鈥檚 terrestrial planets or the icy moons of giant planets.
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The dwarf star鈥檚 size and brightness make it particularly suitable for 鈥渢ransit spectroscopy鈥�, perhaps with the upcoming James Webb Space Telescope. The scope could examine light absorbed by a planet鈥檚 atmosphere and sniff out its gases. The amount of the absorption varies with wavelength and depends directly on the composition and physical conditions of the atmosphere.
We鈥檝e seen potentially habitable worlds in the past, but these three offer the best opportunity for study, says Gillon. 鈥淔or the first time, we have planets for which the atmospheric composition can be studied in detail with current technology.鈥�
鈥淭his has been used successfully in many cases but never for planets as small as the Earth and certainly not for planets in the water-zone,鈥� says of Columbia University, New York. 鈥淭here is a legitimate case to be made that this system could host life and we may be able to infer the presence of that life in the next decade.鈥�
Journal reference: Nature, DOI:
