Perseid meteor shower peaks with ideal viewing conditions this week

The Perseid meteor shower arrives this week with conditions so favorable that astronomers are already making their plans to drive into the darkness. The peak comes Wednesday night into Thursday morning, August 12 to 13, and the timing could hardly be better for anyone willing to step outside and look up.

Under ideal conditions—which means you're far from city lights, the sky is clear, and your eyes have adjusted to the dark—you could see anywhere from 50 to 100 meteors streaking across the sky every hour, according to NASA. The American Meteor Society offers a more conservative estimate of 30 to 50 per hour from rural areas, which is still a remarkable show. These aren't random cosmic events. Every year at this time, Earth passes through a trail of debris left behind by Comet 109P/Swift-Tuttle, a massive icy body that takes 133 years to complete its orbit around the sun. The comet won't return to our corner of space until 2125, but the dust and rock it shed centuries ago remains, and when those particles slam into Earth's atmosphere at tremendous speeds, they burn up in brilliant flashes. Humans have been watching this particular shower for more than two thousand years.

What makes the Perseids special, beyond their sheer frequency, is the quality of the display. The meteors tend to produce vivid fireballs rather than faint streaks, and they arrive during summer, when the nights are warm enough that you don't need to bundle up to stay outside for hours. "We don't have to suffer through a cold winter night to get a good view of meteors," said Zach Vanderbosch, an astronomer at McDonald Observatory in Texas. The other piece of luck is the moon. During the Perseids' peak, the moon will be in its new phase, meaning it won't be visible in the sky at all. Moonlight is a powerful source of light pollution, washing out fainter meteors and dimming the overall display. Without it, the sky darkens dramatically. "The moon is beautiful, but it's such a diva," observed Aparna Venkatesan, an astronomer at the University of San Francisco. "New moon means we don't have moonlight flooding the sky, and you tend to see way more meteors as a result." Venkatesan is planning to drive to the Sierra Nevada to watch.

The mechanics of a meteor shower are straightforward but worth understanding. Comets are ancient, frozen bodies that orbit the sun on paths that sometimes cross Earth's trajectory. As a comet approaches the sun, the heat evaporates the ice, releasing the rock and dust trapped within it. That debris continues circling the sun in the comet's wake. When Earth's orbit intersects with this debris field, the particles collide with our atmosphere at extremely high speeds, creating the luminous trails we call shooting stars. "Comets typically have orbits that cross the orbit of the Earth," explained astrophysicist Neil deGrasse Tyson. "So as they get near the sun and the sun evaporates the ice, a lot of the dirt and crap that's frozen into the comet gets released, and continues in orbit around the sun."

If you want to see the show, the practical advice is simple but requires some effort. Leave the city. Find a dark location away from artificial light. Wait until after midnight, when the constellation Perseus—the point from which the meteors appear to radiate—is highest in the northern sky. Give your eyes at least thirty minutes to adjust to the darkness; your night vision improves dramatically once you stop looking at your phone or any other light source. Pick a patch of sky and watch it patiently. The meteors move quickly, and you might catch them in your peripheral vision. "There's just something magical about it," Vanderbosch said, and that magic is available to anyone willing to step outside and wait.