Gliese 581 D, named Venelia by NASA after the Roman sea goddess wife of Neptune, is a super-Earth terrestrial planet located in the Gliese 581 star system. The star, Gliese 581, is located in the constellation Libra. 581 D is the fourth planet from its red dwarf sun. 581 D is located just outside of the theorized habitable zone, which is a zone all stars have which is the suggested zone a planet must be within to sustain life. Anything outside that zone is either too hot or too cold to sustain life. 581 D was discovered in April 2007 by Swiss scientists using the radial velocity method.