On August 24, 2006, the International Astronomical Union designated Ceres a “Dwarf Planet.” Originally classified as a planet by Italian discoverer Giuseppe Piazzi in 1801, Ceres was re-labeled an asteroid after astronomers learned that it was not one body but a member of the asteroid belt. Only in 2006 did it regain “planet” status. Ceres joined Pluto and Eris, two other spherical objects, as dwarf planets.
August 24th is Ceres’ fifth birthday even though it has been around for 210 years.
Piazzi originally thought the dwarf planet was a comet, which strongly implies that he must have seen a trail following it. As comets move through the solar system, they leave a trail of dust and ice. He may have seen ice sublimating into space like a comet, but exactly what Piazzi saw is unknown because he later classified Ceres as a planet. He named the carbon-rich asteroid after the Roman mythological god of agriculture.
In 1978, researcher Larry Lebofsky of the Jet Propulsion Lab reported water on the surface of Ceres in the form of hydration. Lebofsky based his research on spectrographic data.
The Dawn space probe from the Jet Propulsion Lab and the National Aeronautics and Space Administration is on the way to study Ceres. Unfortunately, Dawn is currently studying the asteroid Vesta and will miss Ceres’ birthday. According to the mission plan, Dawn will visit Ceres in 2015.
At press time, astronomers are still debating exactly how much water and water ice Ceres holds. The space agency estimates that if Ceres consists of as much as 25% water, it may hold more than all the freshwater on Earth.
Ceres is the largest object in the asteroid belt, as opposed to the Near-Earth Asteroids, and has about one-third of the belt’s mass.
SOURCES
Harvard Education Abstracts, Royal Astronomical Society, 1978, Asteroid Ceres 1: evidence for water of hydration
Asteroid 1 Ceres, The Planetary Society
Other Life Exists (book, 2010), Wade Hobbs
Dawn Mission pages, National Aeronautics and Space Agency
Astronomica (book, 2007), Professor Fred Watson et al, pp. 106-07.