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.
2019 AQ3
orbit has the smallest aphelion of any known asteroid in the Solar System, never distancing itself more than 0.774 AU from the Sun (77% of Earth's average orbital distance). Before its discovery, the record was held by at an aphelion of 0.804 AU, which is notably larger. orbit also has a semi-major axis below that of Venus (0.723 AU) and an orbital period of 165 days, which is the second shortest among all asteroids. (The record 161-day orbit of is poorly defined and still may change considerably).