Quaoar

Lore & Background

Quaoar was discovered on 4 June 2002 by American astronomers Chad Trujillo and Michael Brown at Palomar Observatory. The discovery formed part of the Caltech Wide Area Sky Survey, which was designed to search for the brightest Kuiper belt objects using the Palomar Observatory's 1.22-meter Samuel Oschin telescope. Quaoar was first identified in images by Trujillo on 5 June 2002, when he noticed a dim, 18.6-magnitude object slowly moving among the stars of the constellation Ophiuchus. To ascertain Quaoar's orbit, Brown and Trujillo initiated a search for archival precovery images, obtaining several from the Near-Earth Asteroid Tracking survey and two archival photographic plates taken by Charles T. Kowal in May 1983. The earliest known precovery image was found by Edward Rhoads on a photographic plate imaged on 25 May 1954 from the Palomar Observatory Sky Survey.

Before announcing the discovery, Brown conducted follow-up observations using the Hubble Space Telescope to measure Quaoar's size, and used one of the Keck telescopes in Mauna Kea, Hawaii, to analyze its spectrum and characterize its surface composition. The discovery was formally announced by the Minor Planet Center on 7 October 2002, with the provisional designation 2002 LM60. On that same day, Trujillo and Brown reported their scientific results at the 34th annual meeting of the American Astronomical Society's Division for Planetary Sciences in Birmingham, Alabama. Quaoar was given the minor planet number 50000 on 20 November 2002, a deliberate choice highlighting its unusual size and the fact that it was discovered during the search for Pluto-sized objects in the Kuiper belt.

Quaoar's name comes from the creator god of the Tongva people indigenous to the Los Angeles Basin. Brown and Trujillo consulted tribal historian Marc Acuña, who confirmed the name Kwawar would be appropriate. The Tongva preferred the spelling Qua-o-ar, which Brown and Trujillo adopted with the hyphens omitted. Quaoar has one moon named Weywot and a potential second moon that has not yet been confirmed. It is believed that Quaoar's elongated shape, gravitational influence of its moon(s), and extremely cold temperature help keep its rings stable.

Reader's Guide

Quaoar is significant as a large Kuiper belt object whose discovery contributed to the reclassification of Pluto as a dwarf planet. Its reddish surface is made of crystalline water ice, tholins, and traces of frozen methane. Quaoar's two thin rings orbit outside its Roche limit, a configuration that defies theoretical expectations that rings outside the Roche limit should be unstable. The stability of these rings is believed to be maintained by Quaoar's elongated shape, the gravitational influence of its moon(s), and its extremely cold temperature. Quaoar's discovery by Chad Trujillo and Michael Brown was part of a broader search for Pluto-sized objects in the Kuiper belt, and Brown later contributed to the discovery of larger trans-Neptunian objects including Haumea, Eris, Makemake, and Gonggong. The object's naming involved consultation with contemporary members of the Tongva people, and its minor planet number 50000 was deliberately chosen to mark its significance.

Did You Know?

• Quaoar has two thin rings orbiting outside its Roche limit, which defies theoretical expectations that rings outside the Roche limit should be unstable.
• The earliest known precovery image of Quaoar was found on a photographic plate imaged on 25 May 1954 from the Palomar Observatory Sky Survey.
• Quaoar's name comes from the creator god of the Tongva people, and the Tongva preferred the spelling Qua-o-ar.
• Quaoar has one moon named Weywot and a potential second moon that has not yet been confirmed.