(Painting of a Leonid shower in the year 1833. Copyright: E. Weiß (ca. 1888)
The Leonids are a meteor shower associated with the comet Tempel-Tuttle (which takes 33+ years to circle the sun), happen every year around the middle of November. The peak this year is tonight. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky.
Earth moves through the meteoroid stream of particles ejected by the comet as its frozen gasses evaporate under the heat of the Sun when it is close enough. The Leonids, in particular, are well known for having bright meteors or fireballs that may be 9 mm across, have 86 grams of mass, and punch into the atmosphere with the kinetic energy of a car hitting at 60 mph. An annual Leonid shower may deposit 12 or 13 tons of particles across the entire planet. (from www.cute-calendar.com)