![]() Smaller worlds on the other side of the radius valley, with radii of 1.4 times that of Earth or less, would have lost all their hydrogen and helium and would have no significant atmosphere, limiting their radius to just that of their rocky core. Worlds of this scale are often described as mini- Neptunes, and if they have a rocky core, it's deep beneath a thick swathe of atmosphere.Īn illustration of ultraviolet light from a red dwarf (top left) as it slowly evaporates an exoplanets atmosphere. Now, a new take on the radius valley from a team led by PhD student Isaac Malsky of the University of Michigan and Leslie Rogers of the University of Chicago suggests that it could signal an increasing abundance of helium gas in the atmosphere of worlds 2.4 times larger than Earth. Astronomers call this the 'radius valley' and although it seems to be telling us something fundamental about the nature, formation and evolution of planets, scientists have yet to ascertain what that something is. However, transit observations first by NASA's Kepler Space Telescope and now by TESS, the Transiting Exoplanet Survey Satellite, have found a puzzling dearth of planets with radii between 1.4 and 2.4 times that of Earth. Over 5,200 exoplanets have now been confirmed, and many of these are larger worlds that orbit close to their star, in some cases with orbital periods that last just a few days. ![]() ![]() Helium could make up almost half the mass of the atmosphere of giant exoplanets that have migrated close to their star, explaining why there is a mysterious size gap in the scale of these worlds. An illustration of a star slowly evaporating an orbiting planet's atmosphere.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |