Rock Comet Sprouts a Tail
Every year in mid-December the sky fills with flashes of light shooting out of the constellation Gemini. The Geminids are fast, bright, and reliable. They never fail to show up and many observers count them as the finest meteors of the year.
But where do they come from? That is the puzzle.
Meteor showers are supposed to come from comets, yet there is no comet that matches the orbit of the Geminid debris stream. Instead, the orbit of the Geminids is occupied by a thing called "3200 Phaethon." Discovered in 1983 by NASA's IRAS satellite, Phaethon looks remarkably like a rocky asteroid. It swoops by the sun every 1.4 years, much like a comet would, but it never sprouts a dusty tail to replenish the Geminids.
That is, until now.
More: http://science.nasa.gov/science-news/science-at-nasa/2013/27nov_rockcomet/