Planet Gliese 486b is close to us (in a relative sense), rocky, on the small side and may have an atmosphere. These conclusions come from studying the planet using both the transit and radial velocity techniques, which have been the primary methods used by astronomers to find and characterize exoplanets. Charts showing the presence of the planet using both techniques are in the blue boxes. (Render Area, Max Planck Institute for Astronomy, MPIA)
Different methods of searching for and finding distant exoplanets give different information about the planets found.
The transit method — where an exoplanets passed in front of its sun and dims the bright sunlight ever so slightly — gives astronomers not only a detection but also its radius or size.
The radial velocity method — where an exoplanet’s gravity causes its host star to “wobble” in a way that can be measured — provides different information about mass and orbit.
If a planet can be measured by both the transit and radial velocity methods, an important added dimension can be determined — how dense the planet might be. This tells us if the planet is rocky or gaseous, watery or even if it has a central core and might have an atmosphere. So many things have to go right that this kind of dual detection has seldom been accomplished for a relatively small and rocky planet, but such a new planet has now been found.
The planet, Gliese 486b, is a super-Earth orbiting its host star at only 24 light-years away. That makes the planet the third closest transiting exoplanet to Earth that is known, and the closest with a measured mass that transits a red dwarf star.
The authors of the study in the journal Science say Gliese 486b is an ideal candidate for learning how to best search for and characterize an all-important atmosphere, and to study potential habitability, too. Future telescopes will make this kind of work more of a reality.
“Gliese 486 b is not hot enough to be a lava world,” lead author Trifon Trifonov of the Max-Planck-Institut für Astronomie and colleagues write. “But its temperature of ~700 Kelvin (800 degrees Fahrenheit) makes it suitable for emission spectroscopy and …. studies in search of an atmosphere.”
Artist impression of the surface of the newly discovered hot super-Earth Gliese 486 b. With a temperature of about 700 Kelvin (almost 800 degrees Fahrenheit), 486b possibly has an atmosphere.
