( ) is a very large asteroid
of the dark C spectral type
, orbiting in the Cybele group
in the far outer main belt
. As a C-type, it is probably composed of carbonaceous
materials. It was discovered in 1872, and it also has small asteroid moon discovered in 2002.
Hermione was discovered by J. C. Watson
on May 12, 1872 from Ann Arbor
, and named after Hermione
, daughter of Menelaus
in Greek mythology
. Hermione is a Cybele asteroid
beyond most of the main-belt asteroids.
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 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 of the order of 20%, and... Read More