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Hilda asteroid
Group of asteroids in orbital resonance with Jupiter / From Wikipedia, the free encyclopedia
The Hilda asteroids (adj. Hildian) are a dynamical group of more than 5,000 asteroids located beyond the asteroid belt but within Jupiter's orbit, in a 3:2 orbital resonance with Jupiter.[1][2] The namesake is the asteroid 153 Hilda.
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Jupiter trojans Orbits of planets Sun |
Hilda group Asteroid belt Near-Earth objects (selection) |
Hildas move in their elliptical orbits in such a fashion that they arrive closest to Jupiter's orbit (i.e. at their aphelion) just when either one of Jupiter's L5, L4 or L3 Lagrange points arrives there.[3] On their next orbit their aphelion will synchronize with the next Lagrange point in the L5–L4–L3 sequence. Since L5, L4 and L3 are 120° apart, by the time a Hilda completes an orbit, Jupiter will have completed 360° − 120° or two-thirds of its own orbit. A Hilda's orbit has a semi-major axis between 3.7 and 4.2 AU (the average over a long time span is 3.97), an eccentricity less than 0.3, and an inclination less than 20°.[4] Two collisional families exist within the Hilda group: the Hilda family and the Schubart family. The namesake for the latter family is 1911 Schubart.[5]
The surface colors of Hildas often correspond to the low-albedo D-type and P-type; however, a small portion are C-type. D-type and P-type asteroids have surface colors, and thus also surface mineralogies, similar to those of cometary nuclei. This implies that they share a common origin.[4][6]