# Why is the asteroid belt shaped like a triangle?

So, in this question, the user JollyJoker posted this image depicting the orbits of the asteroids in the asteroid field in the comments:

[

In this image, you can see that while the individual asteroids follow elliptical orbits, the asteroid belt as a whole is a giant triangle with the Jovian Trojans at two corners, and a third corner directly opposite Jupiter, and the whole triangle orbits in sync with Jupiter.

Is this image accurate? Is the Asteroid Belt actually a giant triangle, rather than the loose circle it is often depicted as? If so, why is this the case?

• Scheirich has more visualizations of the inner solar system here. The main belt is shown in three shades of red. Feb 12, 2020 at 14:26
• FYI that image host is considered "adult content" by some corporate blockers. Feb 13, 2020 at 9:52
• You point out in the question that the individual red objects each have an elliptical orbit but the collection looks like a triangle that points away from Jupiter. A similar animation that shows more clearly that the individual objects have elliptical, not triangular orbits is here: sajri.astronomy.cz/asteroidgroups/hildaorb.gif Feb 13, 2020 at 21:14

It's not. The image doesn't show the main asteroid belt. It shows the Jovian Trojans (in green) , and the Hilda Asteroids (in red).

The Hildas are a dynamical group of a few thousand known asteroids in elliptical orbits that are locked in a 3:2 orbital resonance with Jupiter, and reach aphelion coinciding with the regions near Sun-Jupiter Lagrange points L4, L3, and L5 in succession.

"Animation showing Hildas with 3 indicated orbits" from "Asteroid (and Comet) Groups", Petr Scheirich, Retrieved 2020/02/14.

In accordance with Kepler's Second Law, objects in elliptical orbits move slower near aphelion than perihelion, and as a result, when you just look at the Hildas, they bunch up near the Lagrange points, and the pattern they appear to show at any one time resembles a triangle.

A more complete view of all the Asteroids inside of Jupiter looks like this.