This artist's rendition released by NASA on July 30, 2015 shows one possible appearance for the planet HD 219134b ======================================================================================================================== Astronomers said Thursday they had found a planetary system with three super-Earths orbiting a bright, dwarf star—one of them likely a volcanic world of molten rock. The four-planet system had been hiding out in the M-shaped, northern hemisphere constellation Cassiopeia, "just" 21 light years from Earth, a team reported in the journal Astronomy & Astrophysics. It comprises four planets—one giant and three super-Earths orbiting a star dubbed HD219134. Super-Earths have a mass higher than Earth's but are lighter than gas...