This is the time for the Leonids meteors, that middle-of-November, middle-of-the night celestial light show. These ultra-swift light streaks appear to emanate from out of the constellation of Leo (hence the name, “Leonid”), which begins to rise in the northeast around 11 p.m., then gradually ascends the sky, remaining in view for the balance of the night.
The meteors usually reach their peak each year on Nov. 17 or 18 as Earth travels through streams of dust left behind by the comet Tempel-Tuttle. Tempel-Tuttle orbits the Sun every 33-years, and during its closest approach the heat of the Sun causes some of the comet’s ice to bubble off, taking some dusty debris with it; stray bits of comet matter that go whipping through the solar system.
The average Leonid that is visible to the naked eye, is scarcely larger than a grain of sand. We know them best when they reach the Earth’s upper atmosphere and flare into streaks of light from friction with the rarefied air. They entire with an immense velocity—45 miles per second, or 162,000 miles per hour—and its kinetic energy is used up in such processes as the instantaneous production of light, heat and ionization.