The shadow of a potentially habitable planet paves the way for the search for extraterrestrial life

A group of researchers from the National Astronomical Observatory of Japan (NAOJ) and the University of Tokyo announces that they have observed the transit of an Earth-like extrasolar planet that could harbor extraterrestrial life.

The planetary transit method is one of the main methods in exobiology for the detection of exoplanets. It is based on measuring the small periodic variations in the luminosity of a star when a planet passes in front of it. It is therefore by using this method that researchers from the National Astronomical Observatory of Japan (NAOJ) and the University of Tokyo were able to observe the transit of an extrasolar planet similar to Earth known as K2- 3d. While thousands of transits have already been observed for thousands of other extrasolar planets, this one is of particular interest to researchers: the exoplanet could indeed harbor extraterrestrial life.

K2-3d is an extrasolar planet located 150 light-years from the Sun (150 X 10,000 billion km). Its size is about 1.5 times that of Earth and the planet orbits in 45 days around a host star about half the size of the Sun. Compared to Earth, the planet orbits quite close to its host star (about 1/5 of the Earth-Sun distance). But because its star’s temperature is lower than that of the Sun, the data suggests that it would be well within reach to have a relatively warm Earth-like climate. It is then possible that liquid water could exist on the surface, raising the possibility that the planet could harbor extraterrestrial life.

The team was able to observe the transit of the exoplanet for the first time from the ground using the Okayama reflector telescope, with an aperture of 188 cm. The decrease in luminosity of 0.07% remains however close to the limit of what can be observed with this type of instrument. The K2 mission will nevertheless continue until February 2018. K2’s successor, the Transiting Exoplanet Survey Satellite (TESS), will be launched in December 2017. The super-instrument will probe the entire sky for two years with the hope of being able to detect hundreds of other small planets like K2-3d near our solar system.


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