The annual Leonid meteor shower will peak this week, in the early morning on Saturday, November 17, and again early morning on Tuesday the 20th. If you decide to stay up (or wake up) to watch it, you’ll be treated to a display of meteors that will be especially easy to see this year, thanks to the coincidence of the new moon and the Leonids.
The shower is so named because it emanates from the constellation Leo, specifically the sickle of Leo. This constellation starts low in the northeast sky around 11 p.m., but will be high in the south-southeast sky by sunrise. So when you go looking at the meteor shower, face towards Leo. (If you don't know what Leo looks like, check out the handy diagram from EarthSky below.) No special equipment is necessary to view the meteors — just dress warmly, lie on your back, and enjoy.
What you’re seeing when a bright streak blazes across the sky this Saturday is likely caused by just a tiny piece of debris, anywhere from the size of a grain of sand to the size of a pea. The meteors are bits and pieces falling off of the disintegrating Tempel-Tuttle comet along its orbital path. It circles the sun every 33 years, each time leaving its trail of debris in a slightly different place. This variation causes the peaks and lows in meteor frequency over the course of the meteor shower, as the Earth passes through different trails in the comet’s orbital plane.
NASA scientists are predicting around 20-30 meteors per hour over the Americas at the shower’s peak. If you find yourself in Asia, though, you’re in luck; scientists are predicting around 10 times more meteors gracing the night sky there. Given the new moon, this should be a pretty good year for the Leonids, but it will be nothing compared to spectacular reports from a few especially incredible years; in the American Southwest in 1966, observers reported 40 to 50 meteors per second for around 15 minutes — around 100 times the display we’re expected to see in the United States.
The Leonids are a special set of meteors because unlike most meteors that find themselves in the Earth’s path, they are moving in the opposite direction as the Earth. As a result, their relative speed is much faster, at around 160,000 mph – that’s 45 miles per second! This high speed means that we can see even very tiny meteoroids, around 0.6 millimeters across, shoot across the sky. It only takes a few milligrams of mass to create a shooting star that is bright as the brightest stars. No Leonid meteors are expected to hit the ground (and in doing so become ‘meteorites’), because they are so small that they completely vaporize from the heat generated from friction with the atmosphere.