121 Hermione
121 Hermione is a very large binary asteroid discovered in 1872. It orbits in the Cybele group in the far outer asteroid belt.[11] 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.[11]
Discovery
Hermione was discovered by J. C. Watson on 12 May 1872 from Ann Arbor, Michigan, in the United States,[11] and named after Hermione, daughter of Menelaus and Helen in Greek mythology.[3]
Physical properties
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/da/121Hermione_%28Lightcurve_Inversion%29.png/220px-121Hermione_%28Lightcurve_Inversion%29.png)
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.[6] 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.[7] 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.
Observation of the satellite's orbit has made possible an accurate determination of Hermione's mass.[7] For the best-fit "snowman" model, the density is found to be 1.8 ± 0.2 g/cm3, giving a porosity on the order of 20%, and possibly indicating that the main components are fractured solid bodies, rather than the asteroid being a rubble pile.
Occultations by Hermione have been successfully observed three times so far, the last time in February 2004.
Discovery[12] | |
---|---|
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[13] | |
768 ± 11 km | |
Eccentricity | 0.001 ± 0.001 |
2.582 ± 0.002 d | |
Inclination | 3 ± 2° (with respect to Hermione pole) |
Satellite of | 121 Hermione |
Physical characteristics | |
Dimensions | 12 ± 4 km[6] |
Mass | ~1.6×1015 kg[c] |
Absolute magnitude (H) | 13.0[6] |
Moon
A satellite of Hermione was discovered in 2002 with the Keck II telescope.[11] It is about 8 miles (13 km) in diameter.[11] 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.[14][6]
Notes
References
- ^ "121 Hermione". Minor Planet Center. Retrieved 14 September 2018.
- ^ Noah Webster (1884) A Practical Dictionary of the English Language
- ^ a b Schmadel, Lutz D. (2007). "(121) Hermione". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 26. doi:10.1007/978-3-540-29925-7_122. ISBN 978-3-540-00238-3.
- ^ "JPL Small-Body Database Browser: 121 Hermione" (2018-05-25 last obs.). Jet Propulsion Laboratory. Retrieved 14 September 2018.
- ^ Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. Archived from the original on 2 July 2013. Retrieved 7 December 2008.
- ^ a b c d e f F. Marchis; et al. (2006). "Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey". Icarus. 185 (1): 39–63. Bibcode:2006Icar..185...39M. doi:10.1016/j.icarus.2006.06.001. PMC 2600456. PMID 19081813.
- ^ a b c d e f F. Marchis; et al. (2005). "Mass and density of Asteroid 121 Hermione from an analysis of its companion orbit". Icarus. 178 (2): 450–464. Bibcode:2005Icar..178..450M. doi:10.1016/j.icarus.2005.05.003.
- ^ IAUC 8264 Archived 9 July 2008 at the Wayback Machine
- ^ a b Supplemental IRAS minor planet survey Archived 2009-08-17 at the Wayback Machine
- ^ PDS node taxonomy database Archived 2009-08-05 at the Wayback Machine
- ^ a b c d e Linda T. Elkins-Tanton (2010). Asteroids, Meteorites, and Comets. Infobase Publishing. p. 96. ISBN 978-1-4381-3186-3.
- ^ IAUC 7980 Archived 2006-05-01 at the Wayback Machine
- ^ 121 Hermione and S/2002 (121) 1, orbit data website maintained by F. Marchis.
- ^ Johnston, Wm. Robert (21 September 2014). "(121) Hermione and S/2002 (121) 1 ("LaFayette")". Asteroids with Satellites Database. Johnston's Archive. Retrieved 7 November 2021.
External links
- 121 Hermione and S/2002 (121) 1, orbit data website maintained by F. Marchis. Includes adaptive optics images, orbit diagrams, and shape models.
- (121) Hermione, datasheet, johnstonsarchive.net
- Asteroids with Satellites, Robert Johnston, johnstonsarchive.net
- Tally of Asteroids Harboring Moons Grows Beyond 30 (Space.com, 3 October 2002)
- 121 Hermione at AstDyS-2, Asteroids—Dynamic Site
- Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
- 121 Hermione at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters
- v
- t
- e
- 120 Lachesis
- 121 Hermione
- 122 Gerda