Quaoar
Quaoar is a dwarf-planet candidate in the Kuiper belt, roughly half the size of Pluto. In 2023 astronomers discovered it has a ring — surprisingly far outside the distance where rings were thought able to survive. It has one small moon, Weywot. No spacecraft has visited; everything we know comes from telescopes and stellar occultations.
Key facts
Science
Physical
- Mass
- 1.20 × 10²¹ kg · 0.0163 Moon masses
- Radius
- 555 km · 9% of Earth's radius
- Density
- 1,676 kg/m³ · 1.7× water
- Surface gravity
- 0.26 m/s² · 3% of Earth's
- Escape velocity
- 537 m/s · 5% of Earth's
Orbital
- Distance from the Sun
- 42.6 AU
- Semi-major axis
- 43.2 AU
- Eccentricity
- 0.03508
- Inclination
- 15.59 °
- Orbital period
- 283.60 years
- Perihelion
- 41.7 AU
- Aphelion
- 44.7 AU
- Mean orbital velocity
- 4.53 km/s
Rotation
- Rotation period
- 17.68 hours
Composition
- Bulk composition
- Near-infrared spectroscopy shows crystalline water ice with traces of methane and other ices on a reddish surface; the crystalline (rather than amorphous) ice hints at past internal warming. The bulk rock/ice interior is unconstrained — no spacecraft has visited.
- Surface imagery
- No real surface imagery exists — this object has never been visited; color is approximate, inferred from spectroscopy.
Radiation & temperature
- Insolation
- 0.000537 S⊕ · 1/1,863 of the sunlight Earth receives
- Geometric albedo
- 0.12
- Equilibrium temperature
- 41 K (-232 °C)
Discovery & history
- Discovered
- June 4, 2002
- By
- Chad Trujillo and Mike Brown
- Method
- Photographic plates
- Name
- Quaoar, the creation force of the Tongva people native to the Los Angeles basin; its moon Weywot is named for Quaoar's son.
Quaoar was discovered on 4 June 2002 by Chad Trujillo and Mike Brown at Palomar Observatory (provisional designation 2002 LM60). About half the size of Pluto, it was among the largest Kuiper-belt finds of its era and helped make the case that the outer Solar System holds many Pluto-like worlds. Its surface shows crystalline water ice and traces of methane, hinting at past internal warming. A moon, Weywot, was found in 2007, and in 2023 astronomers discovered a ring around Quaoar orbiting far beyond the distance where rings were thought able to survive — a puzzle still being studied. It is named for the creation force of the Tongva people of southern California.
Images
Images from open archives · credit shown per image