Since its launch in 1995, NASA's Solar and Heliospheric Observatory, or SOHO, orbiter has captured pictures of 2,000 comets as they've flown past the sun. Most of these comets are so-called sungrazers, relatively tiny comets whose orbits bring them so near the sun that they are often vaporized within hours of discovery.
The sun-watching telescope usually picks up one sungrazer every few days. But between December 13 and 22, SOHO saw more than two dozen sungrazers appear and disintegrate. Seeing "25 comets in just ten days, that's unprecedented," Karl Battams, of the United States Naval Research Laboratory in Washington, D.C., said in a statement. According to Battams and colleagues, the comet swarm could be forerunner fragments from a much larger parent comet that may be headed along a similar path.