In 2005, a controversy erupted in the world of astronomy over who should be credited with the discovery of a distant dwarf planet then known by the temporary name 2003 EL61. The object in question is located in the Kuiper Belt, a doughnut-shaped icy region of the solar system that lies beyond Neptune. It is classified as a “dwarf planet” — which, counter-intuitively, is not actually a planet. According to the International Astronomical Union (IAU), the official naming body in astronomy, a planet must
(a) orbit the Sun,
(b) be massive enough to have a spherical shape,
(c) be massive enough to dominate its region of the solar system, and
(d) not be a moon.
Dwarf planets are almost planets but not quite – they satisfy criteria (a) and (b), but not (c). There are four other objects officially classified as dwarf planets (although many more may qualify): Ceres, the largest object in the asteroid belt between Mars and Jupiter; Pluto, a large Kuiper Belt Object (KBO); Makemake, another large KBO; and Eris, a large object in the region beyond the main Kuiper Belt, the scattered disk.
Pluto has been known for decades and Ceres for centuries, but Eris and Makemake are much more recent finds, discovered in 2005 by a group of astronomers led by Mike Brown at the Department of Geological and Planetary Sciences at Caltech. As for 2003 EL61, not only has Brown’s team claimed its discovery, but so has a rival team led by Jose-Luis Ortiz of the Andalusian Astrophysics Institute in Granada, Spain. Continue reading