Artist's impression of the asteroid Hektor, the largest of the Trojan asteroids. Hektor is highly elongated, & when viewed from Earth its brightness varies by a factor of three. It is 298 km long, but no one knows what it looks like. One theory is that it was formed by a low-speed collision between two smaller asteroids, which then stuck together to form a peanut-shaped double asteroid. Or it may consist of two asteroids orbiting each other very closely. The Trojan asteroids are so called because they follow the orbit of Jupiter & are not in the Asteroid Belt between Mars & Jupiter. There are 2 groups of Trojans, one 60 degrees ahead of Jupiter & one 60 degress behind.