Sky-watchers are getting set for a celestial lion to roar, as the annual Leonid meteor shower kicks into high gear later this week.
Viewing conditions should be near ideal during the shower’s peak, late on November 17 and into the predawn hours of November 18. The moon will be in its new phase that night, which means its darkened face won’t add any glare that can otherwise drown out fainter meteors. Observers under clear, dark skies away from city lights should expect to see anywhere from 10 to 25 meteors an hour during the peak.
Like other annual meteor showers, the Leonids happen when Earth plows through a trail of debris left in the wake of a comet orbiting the sun, in this case, comet Tempel-Tuttle. This icy visitor from the outer solar system was discovered in 1865 and last seen by Earth-bound observers in 1998.
When a comet gets close to the sun, melting ice releases pieces of dust, most no larger than grains of sand, that get deposited in clumps along the comet’s orbital path. Earth slams into the debris stream around the same time every year, causing some of the comet pieces to burn up in our atmosphere and create brilliant meteors. (Find out about a Japanese company aiming to create artificial meteor showers.)
The Leonids are known to be quite temperamental, producing occasional outbursts of intense activity. On rare occasions—every 33 years or so—the annual shower flares up into a bona fide meteor storm, with rates as high as a few hundred shooting stars an hour.
During the last big storm in 2002, more than 3,000 meteors fell in an hour. But the root of the Leonids’ mythical status among the annual showers was the 1833 storm, when counts on one night went as high as 72,000 shooting stars an hour.
While forecasting meteor shower intensity is still in its infancy, these past outbursts roughly coincide with Earth passing through particularly dense clouds of debris, thought to have been left behind when comet Temple-Tuttle made its closest approaches to the sun.
Current calculations indicate that the comet will return to our near neighborhood in 2031 and 2064. But while we may not be hitting the next really dense cloud of material until 2099, astronomers believe we may get an occasional weak outburst in some years as our planet runs through uncharted particle trails.
So, although experts don't expect the celestial lion to roar quite so loudly this year, it is still worth braving the November nights to see how the Leonids perform. The Leonids are also known for occasionally producing brilliant fireballs when the debris stream contains larger objects—more like pebbles or even boulders—so sky-watchers should be on the lookout.
Where to See the Leonids
The Leonids are so named because they seem to radiate from the constellation Leo, the lion, which rises above the northeast horizon in late evenings this time of year. Shooting stars will appear to race across much of the night sky, but if you look carefully, you can trace each one's path back to the constellation.
Observers in the Northern Hemisphere will have the best seats to see the entire the shower, but sky-watchers in the Southern Hemisphere should be able to catch many of the shooting stars, too.
When to See the Leonids
The absolute best views will be during predawn hours for all locations late on the night of November 17 and into the following morning, when the Leo constellation will appear to rise to its highest point in the sky.
The shower’s peak really kicks in between 2 and 4 a.m. local time, when skies will be their absolute darkest.
Leonids are often bright meteors, with a high percentage sporting long-lasting trails. The very brightest ones can even leave behind eye-catching but short-lived smoke trails. (Watch a surprise fireball light up this year’s harvest moon festival.)
How to See the Leonids
Meteor showers are best enjoyed using just your naked eyes—no need for binoculars or telescopes. Since the meteors can appear to zip across large tracts of the overhead sky, it's best to lie down on a reclining lawn chair back-to-back with an observing buddy so that you can cover the entire sky as a team.
Viewers in the colder parts of the Northern Hemisphere can still enjoy the celestial fireworks—just bundle up well with blankets, and don't forget the hot chocolate.
Here’s to clear skies and making many wishes!
Andrew Fazekas, the Night Sky Guy, is the author of Star Trek: The Official Guide to Our Universe and host of NG Live! Mankind to Mars presentations. Follow him on Twitter, Facebook, and his website. Tune in to Nat Geo on Facebook on November 15 at 2 p.m. ET to see Andrew speak live about how to watch the 2017 Leonids.