Neptune Trojan

Astronomers have discovered the first asteroid in the L-5 position in the orbit of Neptune. The L-5 refers to a point in space at which the gravitational influences of Neptune and the Sun balance, which means a body in that slot will tend to remain there indefinitely. It turns out there are five such points in a two-body gravitational arrangement.

Estimates are the asteroid discovered is about 60 miles across and may be one of 150 in the L-5 area. A similar swarm has already been discovered occupying Neptune's L-4 region. Jupiter and Saturn also have asteroids in the corresponding areas of their orbits. Astronomers call such asteroids "Trojans." Bodies at the L-5 and L-4 points have the same orbit as the planet-- Neptune, in this case-- but are 60 degrees ahead of the planet and 60 degrees behind it in the orbit.

The stability at all five of the points make them attractive places to park spacecraft and eventually establish bases. With so many asteroids, and thus so much raw material already there, when humans venture into the realm of the gas giants, major bases may well be established at these points, leading us ever deeper into space.