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Researchers from the institutes of astrophysics of Andalusia (IAA-CSIC) and the Canary islands (IAC) and Space Sciences (ICE-CSIC) have announced in the journal “Science” the discovery around a companion star of two supertierras (planets that are more massive than our own) and a possible third world which, if confirmed, could be habitable. Located 10.7 light-years, it is one of the planetary systems closest acquaintances.

GJ887, the twelfth star closest to us, is a red dwarf, the most common type in the Milky Way, which has a mass equivalent to half of that of our Sun and an average temperature of around 3,400 degrees, about 2,100 degrees cooler than our star. The two supertierras located around it, called GJ887b and GJ887c, present respectively a minimum mass of about four and seven times that of the earth. Both revolve too close to its star, so that it is very difficult that may harbor liquid water on the surface. However, the second planet orbits very close to the inner edge of that zone. In addition, researchers have found evidence of the existence of a third supertierra which, if confirmed, it would be within the habitable zone.

GJ887 thus becomes one of the systems multiplanetarios closest acquaintances, only behind those of proxima Centauri and Wolf359, located 4.2 and 7.9 light-years away and with two planets detected in each one of them. GJ887, however, constitutes the most compact, with its two planets orbiting around a star each for 9.3 and 21.8 days, and the third candidate, every 51 days.

“Given its minimal mass, could in principle be supertierras rocky, but this is not what we know for sure. In the absence of a measure of the radio, which we do not have because the planets do not travel (have not been detected when passing in front of its star), we cannot determine its average density. In addition, depending on the inclination of the orbit with respect to us, the masses could be much larger and move to the range of the minineptunos, with higher content of water in its structure”, says Pedro J. Amado, researcher at IAA-CSIC and author of the research.

The new worlds were found in the framework of the international collaboration RedDots thanks to the Doppler technique, which allows to detect the small movement that the planets occur in your star rotating around it.

A star quiet

GJ887 also has a particularity that makes it interesting. The stars are red dwarfs tend to be very active, more than those of solar flares magnetic relatively frequent. This could hinder the presence of life on planets that surround them. This is what happens in proxima Centauri and Wolf359. However, GJ887 it appears to be a star very quiet. It has been observed during three months with the HARPS spectrograph, some of the instruments cazaplanetas more accurate, and have employee data file of several spectrographs which span more than twenty years, in addition to photometric observations from earth and from space.

“With all these data we detected no flares. Even the photometric detection of magnetic activity surface is very weak, what makes this planetary system a candidate to be very interesting to investigate the existence of rocky planets capable of harboring life”, indicates Eloy Rodriguez, researcher at IAA-CSIC has been involved in the discovery.

the high stability of GJ887 add its proximity and its high apparent brightness, because it is the red dwarf more massive of the environment solar and, therefore, of greater radius. This makes their planets constitute ideal candidates to investigate the possible presence of atmospheres, and molecules to specific instrumentation of new generation, such as the James Webb space telescope, whose launch is planned for march of 2021.