Planet smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon. Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface. Each therefore has a differentiated interior consisting of a dense planetary core surrounded
Distant minor planet Distant minor planet A distant minor planet, or "distant object", is any minor planet found beyond Jupiter in the outer Solar System that is not commonly thought of as an "asteroid". The umbrella term is used by IAU's Minor Planet Center (MPC), which is responsible for the identification, designation and orbit computation of these objects. , the MPC maintains 3497 distant objects in its data base. Most distant minor planets are trans-Neptunian objects and centaurs, while relatively few are damocloids, Neptune trojans or Uranus trojans. All distant objects have a semi-major axis (average distance from the Sun) greater than 6