The two stable1 Lagrangian points in a two body system (L4 and L5) are known as Trojan points.

Trojan points are named after the Trojan asteroids, a group of asteroids named, in turn, after Trojan heroes from the Greek/Trojan War. The Trojan asteroids reside at the Jupiter-Sol L4 point, proceeding Jupiter in its orbit; there is also a group of asteroids at the corresponding L5 point, trailing Jupiter, called the Greek asteroids. Of Sol's planets, Jupiter, Neptune, Mars and Earth2 have been found to have asteroids orbiting around/in thier Trojan points, although some moons have small Trojan point companions (these are planet-moon Lagrangian points, not Sol-moon).

To put it simply3, Trojan points are 'empty' points of space that have their own 'gravity' due to the gravitational forces of two larger celestial bodies. An object in any of the other three Lagrangian points will stay put as long as no other force (besides the gravity of the two bodies) act on them, but will drift away at the slightest nudge. Objects in the Trojan points will drift back to the point if pushed away.

Occasionally Greek Points (L5 points) are differentiated from Trojan points (L4 points), but usually they are both known as Trojan points.


1. These points are only stable when the ratio of Mass1/Mass2 is greater than 24.96. This is the case for all Sun-Planet systems in our solar system, and is also true for the Earth–Moon system. However, the influences of the sun's gravity interferes with the Earth-Moon system, making our L4 and L5 less stable than they would otherwise be.

2. Our Trojan asteroid is 2010 TK7, at Sun–Earth L4, located 60 degrees ahead of Earth in its orbit.

3. The mathematics explaining what exactly is going on are so complex that I can't understand them; if you think that you might be able to, you might want to check out this site.

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