natural satellites of Saturn. The orbits these two moons follow around Saturn are much simpler than the one Cruithne follows, but operate along the same general principles. Mars has four known co-orbital asteroids (5261 Eureka, , , and , all at the Lagrangian points), and Jupiter has many (an estimated one million greater than 1 km in diameter, the Jovian trojans); there are also other small co-orbital moons in the Saturnian system: Telesto and Calypso with Tethys, and Helene and Polydeuces with Dione. However, none of these follow horseshoe orbits. In popular culture Cruithne plays a major role in Stephen Baxter's novel Manifold: Time, which was nominated for the Arthur C. Clarke Award for best science fiction in 2000. Cruithne is mentioned on the QI season 1 episode "Astronomy", in which it is described as a second moon of Earth. In a later episode, it was added that, if using the same definition, Earth has over 18,000 “mini-moons”. In Astonishing X-Men, Cruithne is the site of a secret lab assaulted by Abigail Brand and her S.W.O.R.D. team. It contains many Brood before Brand destroys it. In the Insignia trilogy, 3753 Cruithne has been moved into an orbit around Earth to serve as a training ground for the Intrasolar Forces. In the third novel, Catalyst, it is intentionally directed at Earth. While it is destroyed before impact, its fragments rain down on Earth's surface, killing nearly 800 million people across the world. In the science-fiction book series Aeon 14, Cruithne appears as an inhabited moonlet, home to 'privateers', smugglers, Terran Space Fleet (TSF) outposts and corporate headquarters. Notable inhabitants have included Ngoba Starl and Petral Dulan. Gallery See also temporary Earth satellite discovered in 2006 Co-orbital configuration Earth's second moon Natural satellite Quasi-satellite References Further reading External links Paul Wiegert's page about Cruithne, with movies Java-applet based animations showing Cruithne's orbit A simulation of Cruithne's orbit with animation (Gravity Simulator) Curious About Astronomy: Have astronomers discovered Earth's second moon? Interactive 3D gravity simulation of Cruithne's orbit 003753 Discoveries by Duncan Waldron Named minor planets Earth-crossing asteroids 003753 003753 19861010