121 Hermione

Discovery

Hermione was discovered by J. C. Watson on 12 May 1872 from Ann Arbor, Michigan, in the United States, and named after Hermione, daughter of Menelaus and Helen in Greek mythology.

Physical properties

thumb|left|[[Lightcurve]]-based 3D-model of Hermione

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.

Observation of the satellite's orbit has made possible an accurate determination of Hermione's mass. 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. P. M. Tamblyn, C. Dumas, L. M. Close, C. R. Chapman, F. Menard, W. M. Owen, and D. C. Slater (with respect to Hermione pole)

Moon

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.

Notes

References

References

1. Noah Webster (1884) ''A Practical Dictionary of the English Language''
2. Jim Baer. (2008). "Recent Asteroid Mass Determinations". Personal Website.
3. F. Marchis. (2006). "Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey". Icarus.
4. F. Marchis. (2005). "Mass and density of Asteroid 121 Hermione from an analysis of its companion orbit". Icarus.
5. ''[http://cbat.eps.harvard.edu/iauc/08200/08264.html#Item1 IAUC 8264] {{Webarchive. link. (9 July 2008 '')
6. ''[http://www.psi.edu/pds/resource/imps.html Supplemental IRAS minor planet survey] {{webarchive. link. (2009-08-17 '')
7. ''[http://www.psi.edu/pds/resource/taxonomy.html PDS node taxonomy database] {{webarchive. link. (2009-08-05 '')
8. Linda T. Elkins-Tanton. (2010). "Asteroids, Meteorites, and Comets". Infobase Publishing.
9. [http://cbat.eps.harvard.edu/iauc/07900/07980.html#Item2 IAUC 7980] {{webarchive. link. (2006-05-01)
10. ''[http://astron.berkeley.edu/~fmarchis/Science/Asteroids/Hermione.html 121 Hermione and S/2002 (121) 1]'', orbit data website maintained by F. Marchis.