Dwarf planet
With the discovery of Pluto in 1930, most astronomers considered the Solar System to have nine planets, along with thousands of significantly smaller bodies (asteroids and comets). For almost 50 years Pluto was thought to be larger than Mercury, but with the discovery in 1978 of Pluto's moon Charon, it became possible to measure Pluto's mass accurately and to determine that it was much smaller than initial estimates. It was roughly one-twentieth the mass of Mercury, which made Pluto by far the smallest planet. Although it was still more than ten times as massive as the largest object in the asteroid belt, Ceres, it had one-fifth the mass of Earth's Moon. Furthermore, having some unusual characteristics, such as large orbital eccentricity and a high orbital inclination, it became evident that it was a different kind of body from any of the other planets.
UESAC
The Minor Planet Center credits UESAC with the discovery of 1123 numbered minor planets. The discoveries range from the lowest numbered discovery, 6102 Visby, to the currently highest numbered body, . The given total also including and , which were separately credited to "Comets UESAC", while all other discoveries were credited to "UESAC". More minor planets may yet to be numbered and added to this list as their orbits are confirmed.