It has an elongated ellipsoidal shape with an average diameter of 1,090 km (680 mi), about half the size of the dwarf planet Pluto.

[1] 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.

[22] 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.

[21] In particular, they had also found two archival photographic plates taken by astronomer Charles T. Kowal in May 1983,[24] who at the time was searching for the hypothesized Planet X at the Palomar Observatory.

[29][30] While setting up the observing algorithm for Hubble, Brown had also planned to use one of the Keck telescopes in Mauna Kea, Hawaii, as a part of a study on cryovolcanism on the moons of Uranus.

[d] On that same day, Trujillo and Brown reported their scientific results from observations of Quaoar at the 34th annual meeting of the American Astronomical Society's Division for Planetary Sciences in Birmingham, Alabama.

They announced Quaoar was the largest Kuiper belt object found yet, surpassing previous record holders 20000 Varuna and 2002 AW197.

Upon Quaoar's discovery, it was initially given the temporary nickname "Object X" as a reference to Planet X, due to its potentially large size and unknown nature.

[29] At the time, Quaoar's size was uncertain, and its high brightness led the discovery team to speculate that it may be a possible tenth planet.

After measuring Quaoar's size with the Hubble Space Telescope in July, the team began considering names for the object, particularly those from local Native American mythologies.

Eventually, after reducing chaos to order, they created the seven great giants that upheld the world,[23][28] then the animals and finally the first man and woman, Tobohar and Pahavit.

[29] Indeed, Quaoar's name was announced before the official numbering of the object, which Brian Marsden—the head of the Minor Planet Center—remarked in 2004 to be a violation of the protocol.

[36] Quaoar was given the minor planet number 50000, which was not by coincidence but to commemorate its large size, being that it was found in the search for a Pluto-sized object in the Kuiper belt.

[39] The symbol was designed by Denis Moskowitz, a software engineer in Massachusetts; it combines the letter Q (for 'Quaoar') with a canoe, and is stylized to recall angular Tongva rock art.

[1] Because Quaoar is not in a mean-motion resonance with Neptune, it is also classified as a classical Kuiper belt object (cubewano) by the Minor Planet Center and Deep Ecliptic Survey.

[29][42] Because Quaoar's orbital inclination is greater than 4 degrees, it is part of the dynamically hot population of high-inclination classical Kuiper belt objects.

[42] The high inclinations of hot classical Kuiper belt objects such as Quaoar are thought to have resulted from gravitational scattering by Neptune during its outward migration in the early Solar System.

[13] Measurements of Quaoar's diameter and mass as of 2024[update] indicate it has a density between 1.66–1.77 g/cm3, which suggests its interior is composed of roughly 70% rock and 30% ice with low porosity.

Spectroscopic observations by David Jewitt and Jane Luu in 2004 revealed signs of crystalline water ice and ammonia hydrate on Quaoar's surface.

[50]: 733  A 2006 study by Hauke Hussmann and collaborators suggested that radiogenic heating alone may not be capable of sustaining an internal ocean of liquid water at Quaoar's mantle–core boundary.

Both models and observations suggest that only a few larger bodies (Pluto, Eris and Makemake) can retain the volatile ices whereas the dominant population of small trans-Neptunian objects lost them.

[55] Besides accurately determining sizes and shapes, stellar occultation campaigns were planned on a long-term basis to search for rings and/or atmospheres around small bodies of the outer solar system.

These campaigns agglomerated efforts of various teams in France, Spain and Brazil and were conducted under the umbrella of the European Research Council project Lucky Star.

[10] The discovery of Quaoar's first known ring, Q1R, involved various instruments used during stellar occultations observed between 2018 and 2021: the robotic ATOM telescope of the High Energy Stereoscopic System (HESS) in Namibia, the 10.4-m Gran Telescopio Canarias (La Palma Island, Spain); the ESA CHEOPS space telescope, and several stations run by citizen astronomers in Australia where a report of a Neptune-like ring originated and a dense arc in Q1R was first observed.

[10][56][57] Taken together, these observations reveal the presence of a partly dense, mostly tenuous and uniquely distant ring around Quaoar, a discovery announced in February 2023.

[59] Interstellar Probe, a concept by Pontus Brandt and his colleagues at Johns Hopkins Applied Physics Laboratory would potentially fly by Quaoar in the 2030s before continuing to the interstellar medium, and the first of China National Space Administration's proposed Shensuo probe designed to explore the heliosphere has it considered as a potential flyby target.

[60][61][62] Quaoar has been chosen as a flyby target for missions like these particularly for its escaping methane atmosphere and possible cryovolcanism, as well as its close proximity to the heliospheric nose.