Newly discovered Kepler 452b straddles the line between rocky and gaseous
If Kepler 452b applied for the position of most Earthlike exoplanet, it would boast an impressive résumé. The newly discovered world (illustrated above) mimics our planet with a 385-day orbit around a sunlike star (SN: 8/22/15, p. 16). But there’s a hitch: Kepler 452b may not be made of rock. The planet is about 1.6 times as wide as Earth, and researchers couldn’t measure its mass. As a result, nobody knows if water on Kepler 452b has a solid surface on which to pool.
Kepler 452b is a super-Earth, falling between Earth and Neptune in girth. There are no super-Earths in our solar system but many around other stars. The ones scientists know the most about — worlds with known diameter and mass — tightly orbit stars smaller than the sun. Caltech astronomer Leslie Rogers analyzed several dozen of these