Possible four-planet Kepler candidate system containing two planets that share an orbit, all planets being locked 8:6:4:3 orbital resonances. It was initially thought they were in a 6-4-4-3 resonance, with two planets sharing an orbit, presumably permanently 120 degrees apart. This had sparked comparisons with the theoretical Theia, which was thought to share Earth's orbit, then collided with it to form the moon.
KOI 730 System Web Pages
KOI 730 System In the News
Possible Orbit Sharing Planets Detected (Feb 2011)