The Perseids are here! With no full moon to spoil the show, all you need is a clear sky, darkness, and some patience.
The annual meteor shower peaks on Saturday night and Sunday morning as the Earth passes through the dusty debris of comet Swift-Tuttle’s tail.
Unlike recent years, when the Perseids peaked on a weeknight and left us bleary-eyed at work and school, this astronomical event is happening on a weekend.
“It’s very nice of nature to cooperate like this,” said astronomer Andrew Fraknoi of the Fromm Institute at the University of San Francisco. “It’s a great courtesy on the part of the universe.”
And the moon — an 8%-illuminated crescent — won’t rise until around 3 a.m. on Sunday morning, brightening the eastern sky only as dawn gets underway.
Perseids’ “shooting stars” – fleeting streaks of light that spark a thrill — are bits of rock or dust particles heated to incandescence as they hurl through Earth’s atmosphere at unimaginable speed, said astronomy teacher Don Jolley of DarkSky West Marin, a volunteer-led effort to earn coveted DarkSky Community designation for towns from Woodacre and Stinson Beach to Marshall, preserving the nighttime environment from the harmful effects of light pollution.
“Most are smaller than a pea and disintegrate before they reach our planet’s surface, but larger ‘fireballs’ sometimes survive the fall to Earth,” he said.
Comet Swift-Tuttle was discovered by American astronomers Lewis Swift and Horace Tuttle in 1862. While the 16-mile wide comet could do some significant damage if it struck Earth, astronomers estimate that its orbit will stay stable for the next 2,000 years.
Since comets are leftovers from the early days of our solar system, each flash of light is the “last gasp” of a bit of cosmic material that formed some 5 billion years ago, according to Fraknoi.
Swift-Tuttle is orbiting around the sun, so we intersect its long trail at about the same date each year: August 12-13.
And the meteors may appear to come from the same point: the constellation Perseus, just below the eastern end of Cassiopeia’s “W.” That’s how the meteor shower got its name.
The stars of the celebrated Greek mythological hero live in remote distances and have nothing to do with the creation of the meteors. Rather, they shower the sky within our planet’s atmosphere.
“They can happen anywhere in the sky,” said Fraknoi. “There’s no particular place, or particular direction, that you want to look.”
Not to be upstaged, the Bay Area’s famed summer fog is expected all weekend in San Francisco and coastal areas. This marine layer of low cloud is closely hugging the California coast, creating “Fogust,” so the best viewing will be inland.
Begin your meteor vigil around 10 p.m. If you’re viewing in the early evening, don’t be surprised if you fail to see more than the usual handful of streaks across the sky. Meteors are more common in the wee hours after midnight. The show gets better, and higher in the sky, the later you are out.
That’s because Earth is flying through space as it spins, said Jolley.
“In the hours between sunset and midnight, our view into space shows where we’ve been – a lot like looking into a rear-view mirror as we drive down a highway,” he said.
“On the other hand, in the hours between midnight and sunrise,” he said, “a view into space shows where we’re headed – like peering through a windshield, into a rain of falling stars.”
Perseids arrive piecemeal, either singly or in brief bursts, at an average rate of nearly one a minute. They’re most visible at very dark sites, such as the Point Reyes Peninsula (if there is no fog) or the Sierra Nevada. An interactive light-pollution map — https://www.lightpollutionmap.info — can help you find the darkest skies near your home.
Closer to cities, the number of visible meteors drops. But some streaks will be bright enough to cut through the light pollution of the Bay Area. While they’re not predictable, expect to wait five to 10 minutes to see one.
While waiting, admire “The Summer Triangle.” Seen overhead, it is composed of three bright stars — Vega, Deneb and Altair — in three different constellations.
Passing through this triad of stars is the beloved Milky Way, a river of stars with gossamer beauty.
Busy on Saturday night? Due to the long time it takes Earth to cross the comet’s orbit, you may be able to see Perseids’s streaks for another few days.
And there’s consolation in knowing that our planet gets a near-constant rain of meteoric debris. Studies in Antarctica, where debris is preserved in layers of annual snowfall, estimate that a range of 5 to 40 tons of interstellar stuff falls on Earth every day, said Jolley.
Traces of cosmic dust and dirt can be seen all around us. Just look down.
“As much as 25% of the dust on the ground arrived from space,” said Jolley.
Astronomer Andrew Fraknoi’s tips for spotting the Perseids:
Get away from city lights and find a location that’s relatively dark.
Pick a spot that lets you view as wide as a view as possible.
If it’s significantly foggy or cloudy, you’re out of luck.
Allow at least 10 to 15 minutes for your eyes to get adapted to the dark. Don’t look at your phone.
Don’t use a telescope or binoculars – they restrict your view and you want to see the whole sky.
Dress warmly – it can get cool at night, even in August.
Be patient. It’s not fireworks! Keep looking up and around — admire the constellations — and you’ll see the faint flashes of light.