Expected to peak tonight—in the late hours of Tuesday, August 11 and early hours of Wednesday, August 12—is the annual Perseid meteor shower, one of the year’s most consistently reliable, and certainly the most popular.
For those of us in the northern hemisphere it’s a chance to see “shooting stars” in relatively warm conditions, unlike the “best” meteor shower of the year, chilly December’s Geminids.
The Perseids can see as many as 100 meteors each hour light-up a “dancing sky”, and though strong moonlight this year is expected to dampen that figure somewhat, it’s still likely to be a good show for patient shooting star-gazers (if skies are clear).
However, do you know what a “shooting star” is? What causes them? Or where to look in the night sky?
Here’s everything you ever wanted to know about meteor showers and “shooting stars.”
What are ‘shootings stars?’
Those streaks of light you see in the night sky can—and do—happen constantly. Sure, they increase hugely when a meteor shower is “peaking,” but tiny meteoroids, particles the size of a grain of sand, slam into Earth’s atmosphere. As they do so, they burn-up, gaining energy and then, as they release that energy as photons of light, they momentarily become visible to us.
So a “shooting star” or “falling star” is, obviously, nothing of the sort.
What are ‘earthgrazers?’
This year consider watching before midnight. Technically speaking, the number of “shooting stars” will be greatly reduced from 100, but the Moon will be down, so visibility enhanced. Before midnight is also the best time to see “earthgrazers,” according to the American Meteor Society.
“Earthgrazers” skim the upper regions of the atmosphere, last a few seconds, and their streaks are longer. They’re most likely to be seen low in the east or west, traveling north to south, and occasionally—and most spectacularly—straight up at the zenith, directly above you.
What are ‘fireballs?’
Since they’re moving past through space, and so is Earth, there’s a collision, which causes a bright trail that appears to zip across the night sky in a fraction of a second.
Once you’re past “earthgrazing hour,” expect to see swift “shooting stars” that travel at 37 miles per second/60km per second. However, the Perseids are known for their “fireballs,” larger explosions of light and color that can last for longer than an average meteor streak. Fireballs are the densest and largest material in the meteor stream slamming into Earth’s atmosphere.
Where to look to see Perseids
The “radiant point” for the Perseids is the constellation of Perseus, which is rising in the northeastern night sky come nightfall in mid-August. However, don’t make the mistake of staring at Perseus all night because, in practice, its “shooting stars” can appear at any time of night and in any part of the sky. It’s just that their trails can be traced back to around Perseus. Of course, they’re not actually “in” Perseus at all—just in that part of the night sky.
Here’s a great visual from Sky & Telescope magazine.
How to see the Perseids meteor shower
Stand somewhere away from light pollution; especially important is that there’s no artificial light in your line of vision. For example, it would be a mistake to stand anywhere near a streetlight! In the shadow of a building can work, although there’s no better way than to lay on the ground, preferably in a relatively rural location.
When to look to see Perseids
Although the “peak” night is August 11 through August 12, it’s set to be just as “good” on August 12 through August 13. Indeed, the Perseids have a fairly long peak, which means you’re fine to observe any night this week. The Perseids are actually active from July 17 though August 24.
Since the Moon is up and reasonably bright around midnight, expect to see a “shooting star” around every few minutes between about 11 p.m. and 4 a.m.. Don’t get greedy!
What is a meteor shower?
A meteor shower is when Earth’s normal annual orbital path around the Sun takes it through a stream of dust and cosmic debris—meteoroids—that have been left in the inner Solar System by a comet. Not all comets leave lots of material for Earth to bust into and, indeed, many comets pass through the inner Solar System without crossing Earth’s orbit al path around the Sun.
However, when a giant comet does cross our path, it often leaves its mark.
What causes ‘shooting stars?’
Though they’re caused by meteoroids in space, most meteor showers are caused by comets. In the case of tonight’s Perseids, the culprit is a giant comet called 109P/Swift-Tuttle, which was last in the Solar System in 1992 and will return again in 2126.
No, meteor showers are not dangerous!
Think tiny meteoroids, not huge flaming meteors. Ever since that asteroid the size of a house exploded 14 miles above Chelyabinsk, Russia in 2013, there’s been a nervousness about things falling from the sky. However, events like that have absolutely nothing to do with meteor showers. We’re not talking about big rocks, but dust! What you see as a Perseid “shooting star” is about the same size as a grain of sand.
When is the next meteor shower?
Once the Perseids are over the next meteor shower is the Orionids, which is the result of what Halley’s Comet left in the Solar System in 1986. They’re active from October 2 through November 7, peaking on October 20-21, 2020 while the Moon is just 23% illuminated. Expect about 20 “shooting stars” per hour for that one.
However, the next meteor shower you’re most likely to enjoy, perhaps while camping under dark skies, is indeed 2021’s return of the Perseid meteor shower.
By lucky chance that one peaks in the inky-black dark skies of August 12, 2021, just a few nights after a New Moon.
Wishing you clear skies and wide eyes.