Perseids Meteor Shower Peaks Mid-August, But Full Moon May Dim the Show

Every summer, the Earth passes through a river of cosmic dust, and for a few weeks in July and August, the sky fills with light. This year, the Perseids meteor shower—widely regarded as the finest of the annual celestial events—began its appearance on July 14 and will continue through the end of August. But timing, as it often does, has played a trick on stargazers.

The shower is expected to reach its peak during the predawn hours of August 11 through 13, when observers in ideal conditions might see anywhere from 60 to 100 meteors streaking across the sky each hour. That would ordinarily make for an unforgettable night. The problem is that this year's peak coincides almost exactly with the full moon, which will flood the sky with its own light and wash out many of the fainter meteors that would otherwise be visible.

The Perseids are born from the orbit of comet Swift-Tuttle, a celestial wanderer that last passed near Earth in 1992 and won't return for another 133 years. As it travels around the sun, the comet leaves behind a trail of dust and debris—fragments mostly no larger than a fifth of an inch. Every July and August, Earth's orbit carries our planet directly through this cloud of material. When these tiny pieces strike the upper atmosphere at roughly 60 kilometers per second, friction with the air heats them to incandescence. They burn up about 80 kilometers above the ground, creating the luminous streaks we call shooting stars.

Robert Massey, deputy executive director at the Royal Astronomical Society, explained the physics simply: fragments of space debris slam into the atmosphere at tremendous speed, are destroyed almost instantly by the heat of air resistance, and cause the surrounding air to glow briefly. The Perseid stream is denser than most regions of interplanetary space, which is why observers see far more meteors during this shower than they would on an ordinary night—dozens per hour instead of just a handful.

For those determined to watch despite the lunar interference, Massey offered a strategy. Rather than staying up through the predawn hours when the moon will be brightest, viewers should position themselves outside on the evening of August 11 and watch from dusk until late night. During these hours, they might catch "Earth grazers"—meteors that skim the upper atmosphere at shallow angles and can be particularly striking. But Massey was candid about expectations: the full moon will make this year's display pale in comparison to the spectacular 2021 shower, and he suggested that casual observers probably shouldn't go out of their way to watch.

EarthSky.org offered similar advice, recommending that interested viewers try to catch the shower earlier in August, before the moon reaches its full brightness and begins to dominate the night sky. For dedicated astronomers with patience and dark skies, the Perseids will still offer moments of beauty. For everyone else, the moon has simply won this round.