A team of astronomers announces that they have identified a rocky exoplanet near the Earth evolving so close to its star that it completes its orbit in just eight hours. This type of planet with an "ultra-short orbital period" is still too little studied, hence the interest of this new discovery.
Ultrashort-period exoplanets have orbital periods of less than one Earth day. The precise masses and radii of these worlds could provide constraints on their processes of formation and evolution. Thus, the more samples we have available, the more we will be able to apprehend them. As part of a recent study, a team of researchers reports the detection of one of these planets.
Named GJ 367b, this exoplanet orbits a red dwarf star about half the width of our sun just 31 light-years away . GJ 367b is a rocky world about 70% the size of Earth that completes one revolution of its star in just 7.7 hours .
Astronomer Kristine WF Lam and her team at the Institute for Planetary Research at the German Aerospace Center have identified the presence of GJ 367b in data from the TESS satellite. As a reminder, the latter hunts planets using the transit method which highlights tiny dips in brightness generated by the passage of a world in front of its star from the spacecraft's point of view.
Tracking analyzes made possible by the High Accuracy Radial Velocity Planet Searcher (HARPS), an instrument available at the European Southern Observatory in Chile, then made it possible to calculate the mass of the exoplanet. It is estimated to be about half that of Earth. With these data in hand, astronomers were then able to determine its density, which is greater than that of Earth .
"Such density suggests that the planet is dominated by an iron core “, point out the authors of this work in the journal Science. "These properties are similar to those of Mercury, with its disproportionate iron and nickel core setting it apart from other terrestrial bodies in the Solar System “.
Naturally, GJ 367b is not a good candidate to harbor life as we know it. Due to its extreme proximity to its star, the planet absorbs about 500 times more radiation than the Earth receives from the sun, all without an atmosphere to buffer.
The exoplanet is also probably locked by tides , showing only one side to its star like the Moon with the Earth. Daytime temperatures could reach 1,500 degrees Celsius .
For the time being, it is still unknown how the GJ 376b was able to form. It could be the product of iron-rich building blocks clumped together, or it could be the remnant of a larger planet, much of whose mass was washed away by stellar radiation or a giant impact. "If the planet is indeed a remnant core of an old gaseous planet, then this one should be no larger than a planet the size of Neptune “, note the authors.
Given GJ 367's relative proximity to Earth, astronomers will be able to attempt to answer these questions by targeting the planet with the next generation of telescopes. They might also be looking for other planets that might be in that star's habitable zone.
