Two groups of asteroid s named for heroes of Greece and Troy in Homer's Iliad .
These objects revolve around the Sun at the Lagrangian points (see Joseph-Louis Lagrange ) in Jupiter's orbit. Achilles, the first, was discovered in 1906. About 650 are known, but their actual number is estimated in the thousands. The term Trojan also applies to objects occupying the corresponding Lagrangian points in the orbits of other planets. Two such asteroids were discovered in Mars's orbit in the 1990s.