The second Centaur discovered, and the first recognized as one. Orbits between Saturn and Uranus, just barely crossing each of these planets orbits, and was found when at aphelion (1977) and the furthest detected object at the time. When it approached perihelion (reached in 1996), cometary activity was detected, which did not include water because water does not sublimate at its distances One of the only ones known to have cometary activity and classified as an asteroid an a comet. Has a larger nucleus than any comet. Evidence that its coma comes from a few localized jet-forming areas on its surface, rather than its surface as a whole. Thought to be a newcomer to its orbit since it still has cometary activity and is in a relatively unstable location. It is a potential dwarf planet with a radius of 233 km, and the second largest centaur, possibly the largest.