50000 Quaoar
Quaoar (minor-planet designation 50000 Quaoar) is a large, ringed trans-Neptunian object in the Kuiper belt, a region of icy planetesimals beyond Neptune. It has an elongated ellipsoid shape with an average diameter of 1,090 km (680 mi), about half the size of the dwarf planet Pluto. The object was discovered by American astronomers Chad Trujillo and Michael Brown at the Palomar Observatory on 4 June 2002. Quaoar's surface contains crystalline water ice and ammonia hydrate, which suggests that it might have experienced cryovolcanism. A small amount of methane is present on its surface, which can only be retained by the largest Kuiper belt objects.
Low-resolution Hubble Space Telescope image of Quaoar and its moon Weywot, February 2006 | |
| Discovery | |
|---|---|
| Discovered by |
|
| Discovery site | Palomar Observatory |
| Discovery date | 4 June 2002 |
| Designations | |
MPC designation | (50000) Quaoar |
| Pronunciation | /ˈkwɑːwɑːr/, /ˈkwɑːoʊ.ɑːr/ |
Named after | Qua-o-ar / Kwawar (deity of the Tongva people) |
Alternative designations | 2002 LM60 |
Minor planet category |
|
| Adjectives | Quaoarian |
| Symbol | (mostly astrological) |
| Orbital characteristics | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 3 | |
| Observation arc | 65.27 yr (23,839 d) |
| Earliest precovery date | 25 May 1954 |
| Aphelion | 45.488 AU (6.805 Tm) |
| Perihelion | 41.900 AU (6.268 Tm) |
Semi-major axis | 43.694 AU (6.537 Tm) |
| Eccentricity | 0.04106 |
Orbital period (sidereal) | 288.83 yr (105,495 d) |
Mean anomaly | 301.104° |
Mean motion | 0° 0m 12.285s / day |
| Inclination | 7.9895° |
Longitude of ascending node | 188.927° |
| ≈ 11 February 2075 ±17 days | |
| 147.480° | |
| Known satellites | 1 (Weywot) |
| Physical characteristics | |
| Dimensions | 1,286 × 1,080 × 932 km |
Mean diameter | 1,090±40 km (2024; volume equivalent) |
Mean radius | 545±20 km (2024; volume equivalent) |
Surface area | 3.78×106 km2 |
| Volume | 6.78×108 km3 |
| Mass | (1.20±0.05)×1021 kg: 3 |
Mean density | 1.66–1.77 g/cm3 |
Equatorial surface gravity | 0.37 m/s2 at poles to 0.19 m/s2 at longest axis |
Equatorial escape velocity | 0.59 m/s2 at poles to 0.5 m/s2 at longest axis |
Synodic rotation period | 17.6788±0.0004 h |
| 13.6° or 14.0° to ecliptic (if coplanar with rings) | |
North pole right ascension | 258.47°±0.87°: 3 or 259.82°±0.23°: 4 (outer ring) |
North pole declination | +54.14°±0.11°: 3 or +53.45°±0.30°: 4 (outer ring) |
| 0.124±0.006 | |
| Temperature | ≈ 44 K |
| IR (moderately red) B–V=0.94±0.01 V−R=0.64±0.01 V−I=1.28±0.02 | |
| 19.0 | |
| 2.737±0.008 2.4 (assumed) | |
| 40.4±1.8 milliarcseconds | |
Quaoar has one known moon, Weywot, which was discovered by Brown in February 2007. Both objects were named after mythological figures from the Native American Tongva people in Southern California. Quaoar is the Tongva creator deity and Weywot is his son. In 2023, astronomers announced the discovery of two thin rings orbiting Quaoar outside its Roche limit, which defies theoretical expectations that rings outside the Roche limit should not be stable.