The annual Geminid meteor shower occurs when debris from the asteroid 3200 Phaethon intercepts the Earth. This is an unusual type of shower in having an asteroidal, rather than cometary parent (although there is evidence that Phaethon may actually be the rocky core of an evaporated comet).
This is a composite image of 111 meteors collected between sunset on December 12 and sunrise on December 15 (three nights). Since the images were collected over many hours, the radiant of the shower is not in a fixed location. Conditions were very poor, with extremely low temperatures (-20°C, -5°F) causing icing on the dome over the camera. Consequently, many dimmer meteors were not recorded, and some of those that were caught are distorted.
Long string-like images are stars or planets captured as they traveled across the sky over many hours. The two most prominent are Mars high in the sky, and Sirius lower down.
There are currently several active showers, so not all the meteors visible in the composite are Geminids. The 111 meteors in the image consist of 65 Geminids, 14 Monocerotids, 7 Sigam Hydrids, 2 Puppid-Velids, 19 sporadics, and 4 unknown. Sporadics are meteors which don't appear to belong to any shower, and unknown meteors have paths too short to conclusively trace back to any specific radiant.