15 Eunomia
Eunomia (minor planet designation 15 Eunomia) is a very large asteroid in the middle asteroid belt. It is the largest of the stony (S-type) asteroids, with 3 Juno as a close second. It is quite a massive asteroid, in 6th to 8th place (to within measurement uncertainties). It is the largest Eunomian asteroid, and is estimated to contain 1% of the mass of the asteroid belt.
| Discovery | |
|---|---|
| Discovered by | Annibale de Gasparis |
| Discovery site | Naples Obs. |
| Discovery date | 29 July 1851 |
| Designations | |
MPC designation | (15) Eunomia |
| Pronunciation | /juːˈnoʊmiə/ |
Named after | Eunomia |
Minor planet category | |
| Adjectives | Eunomian /juːˈnoʊmiən/ |
| Symbol | (historical) |
| Orbital characteristics | |
| Epoch July 01, 2021 (JD 2459396.5, heliocentric) | |
| Aphelion | 3.14 AU (469 Gm) |
| Perihelion | 2.15 AU (321 Gm) |
Semi-major axis | 2.644 AU (395 Gm) |
| Eccentricity | 0.186 |
Orbital period (sidereal) | 4.30 yr (1571 d) |
Mean anomaly | 206° |
| Inclination | 11.75° |
Longitude of ascending node | 293° |
| 99° | |
| Physical characteristics | |
| Dimensions | c/a = 0.53±0.02 (357×255×212)±15 km |
Mean diameter | 270±3 km 268 km |
| Mass | (30.5±1.9)×1018 kg (31.8±0.3)×1018 kg [(15.97±0.15)×10−12 M☉] |
Mean density | 2.96±0.21 g/cm3 3.14±0.53 g/cm3 |
Synodic rotation period | 6.083 h (0.2535 d) |
| 0.187 0.25±4 geometric (0.84±0.02 BV, 0.45±0.02 UB) | |
| S-type asteroid | |
| 7.9 to 11.24 | |
| 5.41 | |
| 0.29″ to 0.085″ | |
Eunomia was discovered by Annibale de Gasparis on July 29, 1851, and named after Eunomia, one of the Horae (Hours), a personification of order and law in Greek mythology. Its historical symbol is a heart with a star on top; it is in the pipeline for Unicode 17.0 as U+1CEC8 ().
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