In reference to Mr. Rice's photograph, I hate to be the bearer of bad news, but the "moving light" is not a comet. It's a ghost! If you blow the photograph up, you can see trails on each of the stars in the sky. This effect is called "Ghosting" and occurs when the photographer combines flash with a low shutter speed.

The flash freezes the subject (flag) and the camera records movement (hand movement) with the slow shutter.

The default setting of most cameras is that the flash fires first, and then the slow shutter comes after leaving a moving trail because of camera movement.If Mr. Rice had shot the picture using a tripod or faster shutter speed, the trails would not be there. --April Shepperd