Gliese 581d is an exoplanet located approximately 20.3 light-years away in the constellation Libra. It is considered one of the most Earth-like planets discovered so far. Gliese 581d is about 7 times the mass of Earth and orbits a red dwarf star called Gliese 581. The planet is located within the habitable zone of its star, where conditions may be suitable for liquid water to exist on its surface. However, due to its distance from Earth, studying Gliese 581d in detail is challenging. Scientists believe that the planet has a rocky composition and a thick atmosphere, which could potentially support life, although more research is needed to confirm this.