A trio of Earths 40 light years away?
In the end, fortune favored the brave and the TRAPPIST telescope found its Holy Grail even before observation of all fifty candidates was finished. A first exceptional discovery which demonstrated the potential of the project. At the beginning of 2017, four bigger and more powerful telescopes which will be operational from the famous European observatory of Cerro Paranal, in the Acatama desert in Chile. One of the best astronomy sites in the world says a jubilant Emmanuël Jehin. A twin telescope of TRAPPIST financed by the University of Liege will also very soon be installed in Morocco giving access to the brightest ultracool red dwarf stars in the Northern Hemisphere. “In the coming years, we are going to probe 20 times more ultracool stars than those observed to date. We can expect to find a lot more planetary systems, unless we were incredibly lucky with this one, which is hard to believe. This discovery is the result of a first five years of work, and that seems to indicate that small planets are very frequent around this type of star!” Say the two delighted researchers.
Planets similar in size to Earth
TRAPPIST-1 is a star that is barely bigger than Jupiter (1.2 times its radius). Its light emission was only detected for the first time in 2000, during the course of a systematic observation programme of the heavens in the infrared. Its mass is 80 times greater than that of the gas giant but it remains 12 times dimmer than the Sun. Its surface temperature of only 2550 Kelvin, is barely half the temperature of our star.
Similarities with the Jovian system
The size of the star and the distances separating the planets remain two of the biggest differences with our solar system. “The first planet orbits at 0.011 astronomical units (AU) from its star, the second at 0.15 and the third at probably between 0.02 and 0.06”, explains Michaël Gillon. In less academic terms, this would correspond to orbital periods of a day and a half, two and a half days, and a third orbit of between 4 and 20 days. “We have only been able to observe two transits of the furthest planet which is not sufficient to determine its period”. The fact remains that this system is very different to ours. By way of comparison, Mercury, the planet closest to the Sun needs 88 days to complete an orbit while Earth, the only viable planet in our system, takes 365.25.