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 enter 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.
Thus, such a small particle can be seen as a “shooting star” from more than 100 miles away. Obviously, however, it's really the light energy that it develops and not the particle itself that we see.
This year the best time to look for the Leonids will not be on the traditional nights of Nov. 17 or 18, but rather in the early morning hours of Tuesday, Nov. 20. Two reputable experts in the field of meteor science, Jeremie Vaubaillion of France and Mikhail Maslov of Russia, have independently calculated that the Earth is on target to pass directly through a small clump of dust that was shed by comet Tempel-Tuttle when it swept around the Sun back in the year 1400. That interaction is to occur between 12:30 a.m. and 4:00 a.m. EST.
But don’t expect a tremendous number of meteors. Maslov, in fact, doesn’t think there will be no more than 15 to 20 Leonids per hour as seen from a dark sky location; even less if you trying to watch from a brightly-lit city.
So why bother looking at all? In this case, it isn’t quantity, but quality.
When a comet releases particles into space most are indeed the size of dust and sand grains, but there are also some larger pieces too, ranging from pebble size to perhaps a child’s marble. Those kind of pieces can create outstandingly bright meteors—called “fireballs”—perhaps even meteors that explode in their flight across the sky—called “bolides.”
After a number of revolutions around the Sun, most of the dust-sized particles become dispersed so only the larger pieces remain. In the case of the clump of particles shed by Tempel-Tuttle in 1400, it has circled the Sun 18 times. So if there’s anything left out there in space, there should at least be some of those larger pebble-sized pieces.
If so, then during that 3- or 4-hour interval beginning soon after midnight on Tuesday morning, there’s a “chance” that we might be treated to a few of those types of meteors. The Leonids are well-known for leaving particularly long-enduring incandescent trains, sometimes lingering for many seconds or even minutes. With binoculars you can see these trains drifting against the backdrop of stars, indicative of swift winds in the very high atmosphere.
If you plan to watch, here are a couple of tips: Make sure to stay warm and get comfortable. Should you have a lawn chair that reclines, use it during your search for Leonid meteors since it will help keep your neck from getting stiff as well as make it easier to look at the night sky.
Just seeing one of those dazzlers will make your whole night. Hopefully, nature will be in a show-off mood in the predawn hours of Tuesday.
