The Fabulous Perseids Peak This Week

While the Geminids of December may be richer in meteors, the Perseids are a close second — and much more fun to watch on a warm August night. Credit: NASA
While December’s Geminids of December may be richer in meteors, the Perseids are a close second and more enjoyable to watch on a warm August night. The best time for viewing is Wednesday night from about 10 p.m. till the wee hours of Thursday morning, but the shower is already active. Credit: NASA

Are you ready for the year’s most relaxing meteor shower? Me too. The annual Perseid shower peaks Wednesday night – Thursday morning (August 12-13) when up to 50-100 meteors will flash by per hour. No telescope needed, not even a pair of binoculars. Meteor showers are for everyone no matter your skill level. The only requirements are a reclining lawn chair for comfort and staying up a little later than you’re used to.

Every 133 years, 109P/Swift-Tuttle, discovered in 1862, returns to the inner solar system to spread a rich assortment of comet dust and grit. These end up as our Perseid meteors. Credit: NASA
Every 133 years, 109P/Swift-Tuttle, discovered in 1862, returns to the inner solar system to spread a rich assortment of comet dust and grit. These end up as our Perseid meteors. Its last pass was in 1992, and it returns again in 2125. Debris released by the comet spreads around its orbit, which Earth crosses every August. Credit: NASA

Every year in mid-August, Earth’s orbit intersects that of Comet 109P/Swift-Tuttle. Dust and pebbles released by the comet during its heated approaches to the Sun slam the atmosphere at 130,000 miles an hour, fast enough to completely vaporize in a flash of light we call “shooting stars”. Ever wonder what a meteor streak really is? It looks like fire, right? What we’re actually seeing is a tube of glowing or ionized air.

Even sand-sized particles possess lots of energy if they’re moving fast enough. At 130,000 mph, Earth’s atmosphere feels like a concrete wall to that bit o’ grit. As it swiftly slows down, the grain transfers its energy of motion (kinetic energy) to air molecules, which get all excited and loose electrons. When they regain them and return to their quiet musings, the molecules and atoms emit light — a meteor! Incredible that this game of quantum billiards begins and ends in barely a second.

The Perseid meteor shower beats 'em all for fireballs. Credit: NASA
The Perseid meteor shower beats ’em all for fireballs with 568 captured by NASA’s network of all-sky cameras. The Geminids (GEM) come in second followed by the Orionids (ORI). Credit: NASA

Sometimes meteors, especially those from larger olive pit-sized comet fragments, penetrate more deeply into the atmosphere and last longer. They also create much brighter meteors called fireballs. Hands down, the Perseids are the richest fireball-producing shower of them all. While most of the flashes you’ll see will be faint and swift with a modest number of brighter meteors, chances are you’ll also see a fireball or two.

A brilliant fireball Perseid lights up the sky. Credit: NASA
A brilliant Perseid fireball lights up the sky. Credit: NASA

The Perseids get their name from the constellation Perseus, a roughly J-shaped outline of stars below the familiar W of Cassiopeia. If you spot a meteor and wonder whether it’s a Perseid or a sporadic or random, non-shower meteor, just trace it backwards in the sky. If it takes you down in the northeastern sky in the direction of the W into Perseus, it belongs to the shower.

All Perseids appear to radiate from that direction because that’s where Earth is headed at 18.5 miles a second. The radiant is really a perspective effect similar to parallel railroad tracks appearing to converge in the distance. Like the tracks, Perseids arrive at Earth parallel to one another.

The Perseids appear to radiate from spot below the W of Cassiopeia in the constellation Perseus, hence the shower’s name. This map shows the sky facing northeast around 12:30 a.m. local time August 13. Source: Stellarium
The Perseids appear to radiate from spot below the W of Cassiopeia in the constellation Perseus, hence the shower’s name. This map shows the sky facing northeast around 12:30 a.m. local time August 13. Source: Stellarium

OK, enough details. Let’s talk about how to view this thing. If you go out early, say around 10 o’clock Wednesday night, and face east, you’ll see maybe 20-30 meteors an hour from a outer suburban or dark sky site. You might also catch a rare earth-grazing Perseid. Because the radiant is still low in the northeast at that time, some of the meteors reaching us will scrape only the uppermost atmosphere and take forever — well, at least a few seconds — to burn out.

The later you stay up, the higher the radiant rises, and the more meteors you’ll see with the highest numbers expected around 3 a.m. Thursday, the time of predicted maximum. While that’s darn early, it’s not often that maximum occurs when the radiant is up high and perfectly placed over North America. Great opportunity. By the way, the shower’s already active, so if cloudy weather’s in Wednesday’s forecast, you’ll still see some Perseids every night all week long. Best of all, the moon is a thin morning crescent and won’t spoil the show.

A typical Perseid zips from the radiant headed east toward the Andromeda Galaxy (upper right) on August 12, 2013. Credit: Bob King
A typical Perseid zips from the radiant headed east toward the Andromeda Galaxy (upper right) on August 12, 2013. Credit: Bob King

Since Perseids appear all over the sky, you can set your chair up to face any direction, but my favorite is to put the radiant off to one side and face southeast or south. That way you catch the short-trailed meteors near the radiant and the longer ones further away. As always, the darker the sky, the more you’ll see. Most comet dust particles are sand grain sized or smaller, resulting in far more fainter flashes than bright ones. Avoid yard lights at all costs as they’ll ruin your dark adaption.  One last tip: bring a blanket and a hat to stay warm. Dewy nights can get chilly.

I hope you see LOTS of meteors, but don’t feel bad if light pollution reduces that to 15 an hour or – heaven forbid – the shower totally bombs out. No matter the number, you’re a participant in a grand, cosmic event.

2 Responses

  1. matthew

    Wow, what a great show it was. From my site in the country, I saw well over 300, including almost a dozen fireballs. A little nerve wracking though being in an abandoned apple orchard in the wilderness, with black bears insisting on feeding 50 ft from my setup. Chomp chomp chomp, fireball! Fun times 🙂

    1. astrobob

      Matthew,
      Wow – that’s a lot of Perseids. Thanks for sharing your observation. Those must be some fine apples!

Comments are closed.