In an article published in the Astrophysical Journal Supplement Series, the discovery of other interesting exoplanets is announced, one of which is a cold Neptunian and two are “potentially habitable” super-Earths. The two potentially habitable planets are those orbiting GJ180 (Gliese 180) and GJ229A (Gliese 229), two red dwarfs relatively close to the Sun: the first is 40 light-years away while the second is 19 light-years away and also has a smaller companion, a brown dwarf (GJ229B).
Both these two planets (GJ180d and GJ229Ac) are superterrestrial, i.e. versions with a larger mass and size than the Earth. The exoplanet orbiting GJ180 has a mass 7.5 times greater than the Earth while the one orbiting GJ229A has a mass 7.9 times greater. The orbital periods are 106 and 122 days respectively.
The cold Neptunian (GJ 433 d), instead, orbits around GJ433 (Gliese 433), another red dwarf located 29.5 light-years away from us. All the planets have been discovered using the radial velocity method, that is the method that detects the imperceptible gravity that the planet impresses on its star, gravity that creates small oscillations that can be revealed with advanced instruments from Earth.
The red dwarfs are among the most common stars in our galaxy and, although they are less bright and smaller than our Sun, they can still boast planets that orbit in the so-called “habitable zone”, that orbital area within which a planet can have liquid water on its surface thanks to an almost mild temperature. Usually, the planets that orbit around the red dwarfs always have the same face facing the star, something that splits the planet in two: a hot area and a very cold area, which of course is not favorable for life (although it does not completely exclude it according to different theories).
GJ180d, instead, orbits as it orbits the Earth around the Sun, therefore not always showing the same face facing the star, which raises the probability of habitability and therefore of possible presence of life. GJ229Ac is instead interesting because, besides orbiting around the red dwarf, it also orbits around the companion of the latter, a brown dwarf. It is one of the first exoplanets ever identified that orbit around a brown dwarf, which may help to untangle the doubts about the possibility that such a star can also host planets around it in non-binary systems.
The ultimate goal, as Jeff Crane, one of the authors of the study, adds, is to build a detailed map of all the planets orbiting the stars closest to the Sun so that with future space telescopes these planets can be properly analyzed, especially those potentially habitable.