121 Hermione

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121 Hermione
Orbital characteristics 1 (ftp://ftp.lowell.edu/pub/elgb/astorb.html)
Orbit type Main belt (Cybele)
Semimajor axis 3.439 AU
Perihelion distance 2.941 AU
Aphelion distance 3.937 AU
Orbital period 6.38 years
Inclination 7.58°
Eccentricity 0.145
Physical characteristics 1 (ftp://ftp.lowell.edu/pub/elgb/astorb.html)
Diameter 209 km
Mass 9.3 × 1018 kg
Density 1.8 g/cm³
Rotation period 9.238 hours
Spectral class C
Abs. magnitude 7.31
Albedo 4 (http://dorothy.as.arizona.edu/DSN/IRAS/index_iras.html) 0.048
History 2 (http://cfa-www.harvard.edu/iau/lists/NumberedMPs.html)
Discoverer J. C. Watson, 1872
Satellites
Designation S/2002 (121) 1

121 Hermione is a very large and dark main belt asteroid. It is probably composed of carbonaceous materials.

It was discovered by J. C. Watson on May 12, 1872, 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 from the Keck II telescope. The satellite measures about 18 km in diameter and orbits at a distance of about 800 km. One revolution around the primary takes 1.63 days to complete. The satellite is currently 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.

In December 2003, the adaptive optics of the Keck telescope were able to resolve the shape of Hermione. The bi-lobated shape of Hermione is easily perceived from the images.

The satellite discovery made possible an accurate measurement of mass and density of the asteroid. Early results indicate a very porous body, but further studies have cast doubt on this.

Occultations by Hermione have been successfully observed three times so far, the last time in February, 2004.

External links


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The minor planets
Vulcanoids | Main belt | Groups and families | Near-Earth objects | Jupiter Trojans
Centaurs | Trans-Neptunians | Damocloids | Comets | Kuiper belt | Oort cloud
(For other objects and regions, see: Binary asteroids, Asteroid moons and the Solar system)
(For a complete listing, see: List of asteroids. For pronunciation, see: Pronunciation of asteroid names.)
de:Hermione (Asteroid)

es:(121) Hermiona

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