Updated:01/15/2020 11: 56h
A "cold Neptune" and two potentially habitable super-lands They have just become part of the already extensive catalog of known and confirmed exoplanets. The new worlds have just been presented in a supplement to the Astrophysical Journal along with eight other candidates for new planets, all orbiting around nearby red dwarfs.
In their article, Fabo Feng and Paul Butler of the Carnegie Institute for Science in Washington explain that two potentially habitable planets they orbit, respectively, around GJ180 and GJ229A, two of the stars closest to the Sun, which makes them a priority target for future observations with the new generation of telescopes, currently under construction.
These are two super-earths, with masses equivalent to 7.5 and 7.9 times those of our planet and with orbital periods of 106 and 122 days respectively. The cold Neptune, meanwhile, was found around the star GJ433, at a distance from its star that implies, in all likelihood, that its surface water is frozen. Given its proximity, this world has become the perfect candidate for obtaining, in the near future, direct images. "The planet of the Neptune type GJ433 d – Feng explains – is the closest, largest and coldest ever detected."
The new exoplanets were discovered using the so-called radial velocity method, which takes advantage of the fact that not only the gravity of a star influences the planet that orbits it, but that the gravity of the planet also affects the star. Which creates small oscillations in the orbit of the star that can be detected with the instruments of the scientists. Due to their small size and relatively small mass, red dwarfs are precisely the most suitable stars to locate planets using this technique.
The eternal night
Cooler and smaller than our Sun, the red dwarfs, or M dwarfs, are the most common star class in the entire galaxy, and the ones with the most terrestrial planets around them. In addition, compared to other types of stars, red dwarfs can have planets with the right temperature so that there is water in a liquid state on their surfaces even in very close planetary orbits.
"Many planets that orbit red dwarfs in the habitable zone are blocked by gravitational tides – Feng explains – which means that the period in which they revolve around their axes is the same as the period in which they orbit their host star. This is similar to how our Moon is blocked by tides to Earth, which means we only see one side from here. As a result, these exoplanets have a permanent night very cold on one side and a permanent day and very hot on the other, which is not good for habitability. GJ180d is the closest temperate super-earth to us that is not blocked by tides to its star, which probably increases its likelihood of being able to house and sustain life. "