What do UX Tauri, RW Aurigae, AS 205, Z CMajoris, and FU Orionis have in common? They're young stellar systems with disks where planets could form. It appears those disks were disturbed by stellar flybys or other close encounters in the recent past. Astronomers want to know: did those events disrupt planet formation in the disks? What do they do? Does this happen in other systems? And, did our own solar system experience a strange encounter in its youth?
