Michaël Gillon, the astrophysicist at the University of Liège who discovered the seven Earth-sized worlds orbiting the star Trappist-1, has now discovered, in collaboration with astronomers at the Italian Institute for Astrophysics (INAF), two massive rocky planets 21 light-years from us, the closest known among those transiting in front of their parent star.

Galileo National Telescope (TNG) in the Canary Islands and through cooperation with four Italian researchers, co-authors of the study published in Nature Astronomy: Emilio Molinari from TNG, Giuseppina Micela from Palermo Astronomical Observatory, Giampaolo Piotto from Padua Astronomical Observatory, and Alessandro Sozzetti from Turin Astronomical Observatory.

Unlike the planets found orbiting Trappist-1, these two planets are not similar to the Earth and there is no chance that they can be habitable, being much hotter and larger than the Earth.

They are hotter because their parent star is not a relatively cool red dwarf but an orange dwarf (called HD 219134), smaller than our Sun. And they are much larger since they have masses between 4 and 5 times the mass of the Earth, but, like the Earth, they are rocky and therefore belong to the category of so-called super-Earths. A super-Earth is a rocky extrasolar planet with mass ranging from 1.9-5 to 10 Earth masses.

These two super-Earths set an important record: of the planets transiting in front of their mother star, they are by far the closest to us, just 21 light-years away. “It is really unlikely to have a transiting system closer to us than HD 219134”, said Francesco Pepe, from the Geneva Observatory and co-author of the study.

“The detection of the transits of these two super-Earths”, said Gillon, “is an important step for the study of rocky worlds orbiting other stars. Indeed, the proximity and brightness of their host star combined to their transiting configuration enable a detailed characterization of these planets, notably constraining very thoroughly their internal compositions, which could shed new important light on the origins of massive short-period rocky planets. This result demonstrates that Spitzer, while being in space since 2003, is still a key facility for the study of exoplanets”.

“This is another step toward the characterization of the solar neighbourhood thanks, also, to TNG observations”, added, understandably pleased, Molinari, co-author of the study and Director of Galileo National Telescope.

Source: ResearchItaly