Astronomers at the California Institute of Technology have discovered the largest object in our solar system since the identification of Pluto in 1930. Provisionally called Quaoar, it has reopened the debate on Pluto’s status as a planet, and forms another piece of the ongoing research into the origin and evolution of planetary systems.
Quaoar was sighted as early as 1982, but it wasn’t known to be a member of our solar system until recently. “The discovery of Quaoar is completely due to new technology,” said co-discoverer Chad Trujillo in an e-mail interview. “It’s this new combination of sensitivity, large sky coverage and the use of computer software to find moving objects like Quaoar that makes this project possible with a small number of people.”
Trujillo and his collaborator, Mike Brown, found Quaoar orbiting in the Kuiper Belt, a ring of comets beyond Pluto. Then they trained the Hubble Space Telescope on it to measure its size. Quaoar’s diameter clocked in at an impressive 1,300 kilometres, challenging Pluto’s 2,400 and outdoing the 1,200 kilometre diameter of Pluto’s moon, Charon (Earth is a respectable 12,800 kilometres in diameter).
Pluto may well be the king of the Kuiper Belt Objects (KBOs). Pluto’s small size, icy composition and abnormal orbital properties make it more closely related it to the KBOs than to its neighbouring gas giant planets. While Pluto is generally accorded planet status now, Trujillo notes “it is very likely that there are bodies as large as Pluto that still remain undiscovered.”
A puzzle raised by the discovery of planetary systems around other stars has brought attention back to the Kuiper Belt. Many of the extra-solar planets appear to have formed far from their parent stars, then migrated drastically closer. But how and when did the planets shift position?
Yanqin Wu, a researcher at the Canadian Institute for Theoretical Astrophysics, thinks the answers lie in our own backyard. “Any migration of Neptune and Uranus would disturb the orbits of Kuiper Belt Objects,” he said.
Learn more at science.nasa.gov/headlines/y2002/07oct_newworld.htm
