<p>It's not. The image doesn't show the main asteroid belt. It shows the Jovian Trojans (in green) , and the <a href="https://en.wikipedia.org/wiki/Hilda_asteroid" rel="noreferrer">Hilda Asteroids</a> (in red). </p>

<p>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. </p>

<p><a href="https://i.sstatic.net/6HOET.png" rel="noreferrer"><img src="https://i.sstatic.net/6HOET.png" alt="Animation showing Hildas with 3 indicated orbits, Petr Scheirich, 2005, 2018 "></a></p>

<p>"Animation showing Hildas with 3 indicated orbits" from "<a href="http://sajri.astronomy.cz/asteroidgroups/groups.htm" rel="noreferrer">Asteroid (and Comet) Groups</a>", Petr Scheirich, Retrieved 2020/02/14.</p>

<p>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.</p>

<p>A more complete view of all the Asteroids inside of Jupiter looks like <a href="https://en.wikipedia.org/wiki/Hilda_asteroid#/media/File:InnerSolarSystem-en.png" rel="noreferrer">this.</a></p>

CC BY-SA 4.0
2020-02-12T14:15:35.217Z
https://www.youtube.com/watch?v=yt1qPCiOq-8
uhoh
CC BY-SA 4.0
2020-02-13T07:10:24.653Z
Not really *coinciding* with the Lagrange points, but *approaching* them – not because they are Lagrange points, but because those are the phases where an orbit with that period, with periapsis under Jupiter, must have its apoapsis.
Anton Sherwood
CC BY-SA 4.0
2020-02-13T23:10:03.993Z
[This video](https://www.youtube.com/watch?v=BKKg4lZ_o-Y) is both enlightning in showing where asteroids are, and also very mesmerizing to watch (it shows atseroids both orbiting and being discovered through the years)
Emil Bode
CC BY-SA 4.0
2020-02-14T12:39:33.533Z
@Bilkokuya I've updated the answer with an image illustrating the elliptical orbits, and added some language about how they bunch up into the triangle.
notovny
CC BY-SA 4.0
2020-02-12T13:09:41.777Z
2020-02-14T12:48:02.357Z
2020-02-14T12:48:02.357Z
notovny
<p>So, in <a href="https://astronomy.stackexchange.com/questions/35022/why-isnt-the-asteroid-belt-affected-by-jupiters-gravitational-field">this question</a>, the user JollyJoker posted this image depicting the orbits of the asteroids in the asteroid field in the comments:</p>

<p>[<img src="https://i.gifer.com/4EfK.gif" alt="https://i.gifer.com/4EfK.gif"></p>

<p>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.</p>

<p>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?</p>

CC BY-SA 4.0
2020-02-12T14:26:26.193Z
Scheirich has more visualizations of the inner solar system [here](http://sajri.astronomy.cz/asteroidgroups/groups.htm#innout). The main belt is shown in three shades of red.
Mike G
CC BY-SA 4.0
2020-02-13T09:52:20.280Z
FYI that image host is considered "adult content" by some corporate blockers.
htmlcoderexe
CC BY-SA 4.0
2020-02-13T21:14:07.970Z
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: http://sajri.astronomy.cz/asteroidgroups/hildaorb.gif
Eric Lippert
<orbital-mechanics><asteroid-belt>
Why is the asteroid belt shaped like a triangle?
nick012000
# Why is the asteroid belt shaped like a triangle?

(Asked by: username_0 on 2020-02-12)

So, in [this question](https://astronomy.stackexchange.com/questions/35022/why-isnt-the-asteroid-belt-affected-by-jupiters-gravitational-field), the user JollyJoker posted this image depicting the orbits of the asteroids in the asteroid field in the comments:

[![https://i.gifer.com/4EfK.gif](https://i.gifer.com/4EfK.gif)

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?

**Tags:** orbital-mechanics, asteroid-belt

> **Comments:**
> **username_1**: Scheirich has more visualizations of the inner solar system [here](http://sajri.astronomy.cz/asteroidgroups/groups.htm#innout). The main belt is shown in three shades of red.  
> **username_2**: FYI that image host is considered "adult content" by some corporate blockers.  
> **username_3**: 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: http://sajri.astronomy.cz/asteroidgroups/hildaorb.gif  

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## 1 answers

### Answer by username_4 on 2020-02-12. Score: 75 | Accepted answer

It's not. The image doesn't show the main asteroid belt. It shows the Jovian Trojans (in green) , and the [Hilda Asteroids](https://en.wikipedia.org/wiki/Hilda_asteroid) (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, Petr Scheirich, 2005, 2018 ](https://i.sstatic.net/6HOET.png)](https://i.sstatic.net/6HOET.png)

"Animation showing Hildas with 3 indicated orbits" from "[Asteroid (and Comet) Groups](http://sajri.astronomy.cz/asteroidgroups/groups.htm)", 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.](https://en.wikipedia.org/wiki/Hilda_asteroid#/media/File:InnerSolarSystem-en.png)

> **Comments:**
> **username_5**: https://www.youtube.com/watch?v=yt1qPCiOq-8  
> **username_6**: Not really *coinciding* with the Lagrange points, but *approaching* them – not because they are Lagrange points, but because those are the phases where an orbit with that period, with periapsis under Jupiter, must have its apoapsis.  
> **username_7**: [This video](https://www.youtube.com/watch?v=BKKg4lZ_o-Y) is both enlightning in showing where asteroids are, and also very mesmerizing to watch (it shows atseroids both orbiting and being discovered through the years)  
> **username_4**: @Bilkokuya I've updated the answer with an image illustrating the elliptical orbits, and added some language about how they bunch up into the triangle.  

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