121 Hermione
.png)
A three-dimensional model of 121 Hermione based on its light curve.
|
|||||||||||||
| Discovery | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Discovered by | James Craig Watson | ||||||||||||
| Discovery date | 1872-05-12 | ||||||||||||
| Designations | |||||||||||||
| Pronunciation | /hərˈmaɪ.əniː/ hər-MY-ə-nee | ||||||||||||
|
Named after
|
Hermione | ||||||||||||
| 1970 VE | |||||||||||||
Main belt  (Cybele) |
|||||||||||||
| Orbital characteristics | |||||||||||||
| Epoch December 31, 2006 (JD 2454100.5) | |||||||||||||
| Aphelion | 588.328 Gm (3.933 AU) | ||||||||||||
| Perihelion | 446.029 Gm (2.982 AU) | ||||||||||||
| 517.179 Gm (3.457 AU) | |||||||||||||
| Eccentricity | 0.138 | ||||||||||||
| 2347.854 d (6.43 a) | |||||||||||||
|
Average orbital speed
|
15.94 km/s | ||||||||||||
| 248.068° | |||||||||||||
| Inclination | 7.604° | ||||||||||||
| 73.209° | |||||||||||||
| 296.215° | |||||||||||||
| Known satellites | S/2002 (121) 1 | ||||||||||||
| Physical characteristics | |||||||||||||
| Dimensions | 268×186×183 km 254±4 × 125±9 km |
||||||||||||
|
Mean radius
|
95 km | ||||||||||||
| Mass | 5.38 ± 0.3 ×1018 kg 5.4 ± 0.3×1018 kg |
||||||||||||
|
Mean density
|
1.13 ± 0.3 g/cm³ 1.8 ± 0.2 g/cm³ |
||||||||||||
|
Equatorial surface gravity
|
0.022 m/s² | ||||||||||||
|
Equatorial escape velocity
|
0.075 km/s | ||||||||||||
|
Sidereal rotation period
|
0.2313 d (5.551 h) | ||||||||||||
| 73° | |||||||||||||
|
Pole ecliptic latitude
|
+10 ± 2° | ||||||||||||
|
Pole ecliptic longitude
|
1.5 ± 2° | ||||||||||||
| 0.0482 ± 0.002 | |||||||||||||
|
|||||||||||||
| C | |||||||||||||
| 7.31 | |||||||||||||
| Discovery | |
|---|---|
| Discovered by |
W. J. Merline, P. M. Tamblyn, C. Dumas, L. M. Close, C. R. Chapman, F. Menard, W. M. Owen, and D. C. Slater |
| Discovery date | 2002-09-28 |
| Designations | |
| LaFayette | |
|
Main belt (Cybele) |
|
| Orbital characteristics | |
| 768 ± 11 km | |
| Eccentricity | 0.001 ± 0.001 |
| 2.582 ± 0.002 d | |
|
Average orbital speed
|
22 m/s |
| Inclination | 3 ± 2° with respect to Hermione pole |
| Satellite of | 121 Hermione |
| Physical characteristics | |
| Dimensions | 12 ± 4 km |
| Mass | ~1.6×1015 kg |
|
Equatorial escape velocity
|
~ 6 m/s |
| 13.0 | |
121 Hermione is a very large asteroid discovered in 1872. It orbits in the Cybele group in the far outer asteroid belt. As an asteroid of the dark C spectral type, it is probably composed of carbonaceous materials. In 2002, a small moon was found to be orbiting Hermione.
Hermione was discovered by J. C. Watson on May 12, 1872, from Ann Arbor, and named after Hermione, daughter of Menelaus and Helen in Greek mythology.
Hermione is a Cybele asteroid and orbits beyond most of the main-belt asteroids.
A satellite of Hermione was discovered in 2002 with the Keck II telescope. It is about 8 miles (13 km) in diameter. The satellite is provisionally designated S/2002 (121) 1. It has not yet been officially named, but "LaFayette" has been proposed by a group of astronomers in reference to the frigate used in secret by the Marquis de Lafayette to reach America to help the insurgents.
The asteroid has a bi-lobed shape, as evidenced by adaptive optics images, the first of which were taken in December 2003 with the Keck telescope. Of several proposed shape models that agreed with the images, a "snowman"-like shape was found to best fit the observed precession rate of Hermione's satellite. In this "snowman" model, the asteroid's shape can be approximated by two partially overlapping spheres of radii 80 and 60 km, whose centers are separated by a distance of 115 km. A simple ellipsoid shape was ruled out.
...
Wikipedia