It's one of the lightest of the nearly 5,000 exoplanets known to date. It is GJ 367 b, recently discovered and nicknamed the "feather planet."
An international team of researchers has discovered an exoplanet so close to its star that its surface may be molten. It is GJ 367 b and has a mass half that of Earth. Among its peculiarities, there is also that it takes only 8 hours to make a revolution around its star. The research was published in the journal Science and in the group of scholars there are also the Italians Luisa Maria Serrano, Elisa Goffo and professor Davide Gandolfi of Department of Physics of the University of Turin.
The planet where a year lasts 8 hours
GJ 367 b was discovered thanks to observations conducted with the space telescope TESS (Transiting Exoplanet Survey Satellite) of NASA using the method of transits, which consists in measuring the decrease in light of a star when it is partially occulted by one of its planets that transits in front of it. The exoplanet is one of the lightest of the nearly 5000 known to date and is also called a "feather planet." With a diameter of just over 9000 km, it is slightly larger than Mars. It revolves around its star in 8 hours, so its year has a very short duration, equivalent to one third of our day.
The peculiarities of GJ 367 b
Professor Gandolfi explained that GJ 367 b is one of the smallest terrestrial exoplanets whose mass has been precisely measured and is a rocky planet. It falls among what are called ultra-short period planets in scientific jargon, meaning planets with a very short orbital period, since it is shorter than 24 hours. "These are generally rocky planets with dimensions smaller than one and a half times that of the Earth. Among the planets belonging to this family, GJ 367 b is the smallest member whose mass has been measured," Gandolfi pointed out.
"Although we do not know its origins well, we believe that GJ 367 b formed at much greater distances from its star," the scientist added, "and that it subsequently migrated to the innermost regions of the planetary system, reaching its current orbit. The radius and mass of the exoplanet were determined with an accuracy of 7% and 14%, respectively, and the detection was made using the HARPS spectrograph of the European Southern Observatory. Thanks to the instruments used, the team was able to deduce important information about its internal structure and composition.
"GJ 367 b has a density of about 8 grams per cubic centimeter, greater than that of Earth. This suggests that the planet has a very large core of iron and nickel, similar to that of Mercury, the innermost planet in the Solar System," explained researcher Maria Luisa Serrano. GJ 367 b orbits a red dwarf star and the proximity of the planet to its star would expose it to an extremely high level of radiation, more than 500 times more intense than that which the Earth receives from the Sun and that has been estimated by researchers in about 1500 degrees Celsius. A temperature at which rocks and metals melt and would cover the planet's surface with lava.
In the meantime, other researchers have discovered a Jupiter-like planet that could show the future of the solar system and another planet that survived the death of its own star.