10 Hygiea
Hygiea's southern hemisphere imaged by the Very Large Telescope in July 2017 | |||||||||
| Discovery | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Discovered by | Annibale de Gasparis | ||||||||
| Discovery site | Astronomical Observatory of Capodimonte | ||||||||
| Discovery date | 12 April 1849 | ||||||||
| Designations | |||||||||
| (10) Hygiea | |||||||||
| Pronunciation | /haɪˈdʒiːə/ | ||||||||
Named after | Hygieia | ||||||||
| A849 GA · A900 GA | |||||||||
| Main belt (middle) · Hygiea family | |||||||||
| Adjectives | Hygiean /haɪˈdʒiːən/ | ||||||||
| Symbol | (historical astronomical), (modern astrological) | ||||||||
| Orbital characteristics | |||||||||
| Epoch 5 May 2025 (JD 2460800.5) | |||||||||
| Uncertainty parameter 0 | |||||||||
| Aphelion | 3.488 AU (522 million km) | ||||||||
| Perihelion | 2.799 AU (419 million km) | ||||||||
| 3.144 AU (470 million km) | |||||||||
| Eccentricity | 0.1096 | ||||||||
| 5.57 yr (2,036 days) | |||||||||
| 181.38° | |||||||||
| 0° 10m 36.588s / day | |||||||||
| Inclination | 3.832° to ecliptic | ||||||||
| 283.13° | |||||||||
| 9 February 2028 | |||||||||
| 312.71° | |||||||||
| Proper orbital elements | |||||||||
Proper semi-major axis | 3.1418 AU | ||||||||
Proper eccentricity | 0.1356 | ||||||||
Proper inclination | 5.1039° | ||||||||
Proper mean motion | 64.6218 deg / yr | ||||||||
Proper orbital period | 5.57088 yr (2034.762 d) | ||||||||
Precession of perihelion | 128.544 arcsec / yr | ||||||||
Precession of the ascending node | −96.9024 arcsec / yr | ||||||||
| Physical characteristics | |||||||||
| Dimensions | 450 km × 430 km × 424 km (± 10 km × 10 km × 20 km): 18 | ||||||||
| 433±8 km (2021): 6 434±14 km (2020): 136 | |||||||||
| Flattening | 0.06±0.05 | ||||||||
| Mass | (8.74±0.69)×1019 kg (2021): 6 (8.32±0.80)×1019 kg (2020): 137 | ||||||||
Mean density | 2.06±0.20 g/cm3 (2021): 6 1.944±0.250 g/cm3 (2020): 137 | ||||||||
Equatorial surface gravity | 0.12 m/s2 (average) | ||||||||
Equatorial escape velocity | 0.229 m/s (average) | ||||||||
| 13.82559±0.00005 h: 136 : 18 | |||||||||
| 120° to ecliptic: 18 | |||||||||
North pole right ascension | 319°±3°: 136 | ||||||||
North pole declination | −46°±3°: 136 | ||||||||
Pole ecliptic latitude | −29°±3°: 18 | ||||||||
Pole ecliptic longitude | 306°±3°: 18 | ||||||||
| 0.063 (2021): 6 0.072 (2020): 139 | |||||||||
| |||||||||
| C | |||||||||
| 9.0 to 12.0 | |||||||||
| 5.65 | |||||||||
| 0.321″ to 0.133″ | |||||||||
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10 Hygiea is a large asteroid located in the outer main asteroid belt between the orbits of Mars and Jupiter. It was the tenth known asteroid, discovered on 12 April 1849 by Italian astronomer Annibale de Gasparis at the Astronomical Observatory of Capodimonte in Naples, Italy. It was named after Hygieia, the Greek goddess of health. It is the fourth-largest main-belt asteroid by both volume and mass, with a mean diameter of 433 km (269 mi) and a mass constituting 3% of the main asteroid belt's total mass.
Hygiea has a nearly spherical shape, with two known craters about 100 and 180 km (62 and 112 mi) in diameter. Because of its shape and large size, some researchers consider Hygiea a possible dwarf planet. Hygiea has a dark, carbonaceous surface consisting of hydrated and ammoniated silicate minerals, with carbonates and water ice. Hygiea's subsurface likely contains a large fraction of water ice. These characteristics make Hygiea very similar to the main-belt dwarf planet Ceres, which suggests the two objects have similar origins and evolutionary histories.: 2
Hygiea is the parent body of the Hygiea family, an asteroid family comprising over 7,000 known asteroids that share similar orbital and compositional characteristics with Hygiea. The Hygiea family is believed to have formed by a giant impact on Hygiea about 2 to 3 billion years ago. This impact is thought to have shattered Hygiea, which led to its reaccumulation as a nearly spherical body.