Have you ever seen a “shooting star” streak across the sky in a fraction of a second, leaving a thin glowing trail behind it? Or perhaps a celestial object moving slowly through the heavens over days or even weeks, with a long luminous tail stretching behind it? Both of these natural phenomena occur on a cosmic scale, and they are closely connected. Comets are celestial bodies that typically range in size from a few hundred meters to around 20 kilometers in diameter, although some of the largest known comets may exceed 100 kilometers…