Mercury (planet)
Mercury is one of four terrestrial planets in the Solar System, and is a rocky body like Earth. It is the smallest planet in the Solar System, with an equatorial radius of . Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan. Mercury consists of approximately 70% metallic and 30% silicate material. Mercury's density is the second highest in the Solar System at 5.427 g/cm, only slightly less than Earth's density of 5.515 g/cm. If the effect of gravitational compression were to be factored out from both planets, the materials of which Mercury is made would be denser than those of Earth, with an uncompressed density of 5.3 g/cm versus Earth's 4.4 g/cm.
51 Eridani
51 Eridani b is a young Jupiter-like planet and was photographed, in near-infrared light, on December 21, 2014. The study, led by Bruce Macintosh, a professor of physics at Stanford University and confirmed by Christian Marois found that methane and water were abundant in the atmosphere of the planet and its mass was only slightly larger than Jupiter’s. It is the smallest exoplanet directly imaged to date.