It’s been a record-hot summer. Feel like a shower?
Every summer’s biggest, shiniest shower is the one that scatters down from the August night sky. It’s the Perseid meteor shower, and its cause is dazzlingly simple: Earth’s orbit crossing the littered orbit of a comet.
When that happens, random bits of dusty, rocky comet detritus speed into our atmosphere at thousands of miles per hour. Most are speck-sized and quickly burn up at altitudes between 30 and 80 miles high, leaving the bright signature streaks we call shooting stars. Scientists call them meteors.
You can just call them “Wow!”
The Perseids are the busiest, most reliable of all annual meteor showers. At their peak, you may be able to witness as many as 60 to 100 meteors per hour — if you’re watching from a dark place at the right time of night.
That time, unfortunately for most of us, is between midnight and sunrise, because that’s when our side of the Earth is turning away from the sun and toward the debris stream. But don’t let that stop you from looking up at whatever time after dark you can. Wednesday through Sunday, the Perseids should be strong and steady enough to be visible as soon as the sun goes down, according to Jim Todd, director of space science education at the Oregon Museum of Science and Industry in Portland.
The moon will be a skinny, shrinking sliver on those nights (before it completely disappears Aug. 16), so there should be minimal sky glare interfering.
Big, steady comet
There’s nothing unusual about Earth barreling through the messy paths of comets, which are balls of ice and rock that stay frozen when distant from the sun but start melting as they draw close, strewing gas, dust and rocky debris in their wake.
Summer’s space litterbug is comet Swift-Tuttle, considered a large and “periodic” comet, meaning that it’s been observed multiple, predictable times across history. Its first sighting was in A.D. 36.
Traveling at approximately 26 miles per second, Swift-Tuttle takes 133 Earth years to circle the sun. The last time it visited our neighborhood in person was 1992, when it reportedly could be seen only with binoculars.
If you’re lucky enough to be around in 2125, get ready for a real spectacle, as Swift-Tuttle is predicted to be bright enough to spot with the unaided eye. And whoever is watching the skies in the years 3044 and 4479, well, cross your fingers, because those are the years when scientists are ever so slightly worried about close comet-Earth encounters.
Swift-Tuttle is massive, according to NASA, and so is its debris field. The comet is 16 miles across, which is twice as big as the object suspected of striking the Earth 66 million years ago, triggering abrupt climate change and the mass extinction that wiped out the dinosaurs.
Put all that out of your mind for the next thousand years. Worry instead about clear skies over Clark County this month.
Across North America, the Perseid meteor shower is widely acknowledged as the one to watch. (Because of the Earth’s tilt, most of the Southern Hemisphere doesn’t experience the Perseids.) If you’ve been hankering for some cosmic special effects lately, your chances are best in the weeks to come, with maximum meteor activity expected to be the nights and early mornings of Friday through Sunday.
Skywatching outside of those dates may well pay off too, said Todd. We’ve been inside the comet’s debris field since mid-July and won’t be out until September.
“The peak is quite broad and so it is well worth observing on the nights before and after,” Todd said.
Look north
The Perseid meteor shower seems to issue from one spot in the sky, called the radiant. That’s between the constellations Perseus (where the shower gets its name) and Cassiopeia. Both constellations rise in the north-northeast just after sunset (around 8:30 p.m. these days).
Perseus, by the way, is “The Hero” and resembles a pointy-headed figure running west with its arms splayed; Cassiopeia, “The Queen,” is seated upon her throne and resembles a tilting W. That region of space is where the night’s shooting stars will originate.
To see them, find a viewing place that’s extra dark and not blocked toward the north. Avoid artificial light. Binoculars probably won’t help you catch shooting stars but may let you admire the trails that linger for a second or two.
“The radiant will be low in the northeast but don’t concentrate on one area,” Todd said. “Let your gaze wander over a large portion of the sky. Meteors that appear near the radiant will have short paths while those that begin farther out will have much longer ones.”
The radiant will reach its highest point — about 70 degrees above the northern horizon — after midnight. The best light show should be between midnight and dawn.
Star parties
Telescopes aren’t great at catching quick little objects like meteors as they flash across the sky. But telescopes will be out in droves at a skywatching party in the Columbia River Gorge that’s timed for the height of the Perseids.
The telescopes will be for gazing at other great stuff in the sky, Todd said. For the Perseids, OMSI and co-sponsors the Rose City Astronomers and Oregon State Parks will offer informal talks and meteor-watching guidance, along with star maps and suggestions about skywatching apps.
The event is set for 9 to 11 p.m. Saturday at Rooster Rock State Park. Bring lawn chairs, blankets, bug repellent. Visit omsi.edu/events/omsi-star-party for details (and to make sure the event hasn’t been canceled due to cloudy skies).
Closer to home, and not specifically meteor-focused, is another viewing party with the Rose City Astronomers and the WSU Extension Clark County Master Gardeners. This one is set for 7:30 to 9:30 p.m. Aug. 22 at the 78th Street Heritage Farm at Northeast 19th Court in Hazel Dell. It’s aimed at ages 7 and older and intended to remind everyone about the beauty of being outside after dark. Participants will move throughout the 78th Street Heritage Farm property, including a 15-minute walk up a hill, in a small group accompanied by a pair of guides. No strollers, walkers or wheelchairs.
Registration is required but space is limited. Register at www.eventbrite.com/e/starry-nightat-the-farm-tickets-658730710287. Contact erika.d.johnson@wsu.edu or 564-397-5738.
