Hilda asteroid

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°.

[5] The surface colors of Hildas often correspond to the low-albedo D-type and P-type; however, a small portion are C-type.

[3] The "asteroidal stream" within the sides of the triangle is about 1 AU wide, and in the apices this value is 20–40% greater.

Figure 1 shows the positions of the Hildas (black) against a background of all known asteroids (gray) up to Jupiter's orbit at January 1, 2005.

On average, the velocity of perihelion motion is greater when the orbital eccentricity is lesser, while the nodes move more slowly.

In addition to the fact that the Hildas triangle revolves in sync with Jupiter, the density of asteroids in the stream exhibits quasi-periodical waves.

At the apexes of the triangle corresponding to the points L4 and L5 of Jupiter's orbit, the Hildas approach the Trojans.

This is illustrated by the adjacent figure that shows the Hildas (black) and the Trojans (gray) along the ecliptic plane.

When moving along each side of the triangle, the Hildas travel more slowly than the Trojans, but encounter a denser neighborhood of outer-asteroid-belt asteroids.

The observed peculiarities in the Hildas' motion are based on data for a few hundred objects known to date and generate still more questions.

[citation needed] The Hildas traverse regions of the Solar system from approximately 2 AU up to Jupiter's orbit.