The Leonids have their name because if you trace all the meteor trails backward, they would meet within the boundaries of the constellation Leo the Lion
. Astronomers call that point the radiant. To find Leo in the sky, first locate the Big Dipper in the northeast. Poke a hole in the bottom of the Big Dipper’s bowl. As the water runs out, you may hear a mighty roar as the water falls on the back of Leo.
Particles in the Leonid shower are debris shed by the comet 55P/Tempel-Tuttle. In 1865, astronomer Ernst Tempel discovered the comet, and in 1866, another astronomer, Horace Tuttle, independently found it. The comet itself measures about 2.5 miles (4 kilometers) in diameter and orbits the Sun with a period of slightly more than 33 years.
As it makes its closest approach to the Sun, it also passes close to Earth’s orbit. This last happened February 28, 1998. Our 2012 encounter with the debris stream from Tempel-Tuttle will last several days, but the most intense part (when we’ll see the most meteors) typically lasts only two to three hours.
Leonid meteors are fast (they move at more than 40 miles [65km] per second), and some leave smoke trails that can last a number of seconds. Many Leonids are also bright. Usually, the meteors are white or bluish-white, but in recent years some observers reported yellow-pink and copper-colored ones.