The passing of July to August signals the arrival of one of the most prominent and reliable meteor showers, the Perseids. It has wowed observers for centuries and inspired many to capture their awe in writing, from the Chinese observer who in 36 AD made the first written record of this annual sky show, to the 1970s singer, Henry Deutschendorf, the son of a decorated Air Force pilot.
Like other meteor showers, the Perseids derive from a wide stream of predominantly sand-sized particles, remnants of a comet that liberates fractions of its surface every time it passes by the Sun and its warming rays. Every year Earth passes through the stream and many of the particles burn up in our planet’s atmosphere, creating the meteor shower.
In recent years, peak activity for the Perseids reached about 60 meteors per hour. This number may increase to upwards of 200 in 2016 thanks to the bully of our planetary family, Jupiter. This Jovian giant leverages its considerable gravitational influence to shove smaller neighboring bodies around. In 2016, Jupiter has pushed much of the Perseid debris stream closer to Earth’s orbit, meaning we should witness an increased burst of activity when Earth passes through the stream.
Perseid particles turn into illuminated meteors (also known as falling stars and shooting stars) when they tear into Earth’s atmosphere at a rate of about 37 miles per second (at this speed, you could travel from Flagstaff to Phoenix in about four seconds), compressing and heating the air in front of them as they reach temperatures of around 3,000 Fahrenheit. They are usually visible from Earth at about 60 miles from the ground.
Swift-Tuttle is the parent comet of the Perseids. Discovered independently in 1862 by two astronomers, Lewis Swift and Horace Tuttle, it orbits the Sun every 133 years. Like other comets with associated meteor showers, when Swift-Tuttle reaches perihelion—its closest point to the Sun—it brings a greater concentration of debris and thus a higher rate of meteor activity. During Swift-Tuttle’s last perihelion, in 1992, the Perseids peaked at 500 meteors per hour.
The Perseids occur each year from around July 17 to August 24, sharing the sky for part of that time with the Delta Aquarid Meteor Shower. In late July the Perseids were visible in only modest numbers, but they will slowly increase until peaking on the evening of August 11/morning of August 12. The waxing gibbous moon will interfere with viewing but the pre-dawn hours (when the peak of a meteor shower typically occurs) of the 12th will offer dark sky viewing.
While the Perseids were first recorded in 36 AD, their connection to Comet Swift-Tuttle wasn’t established until 1862, when Italian astronomer Giovanni Schiaparelli—the same astronomer who first wrote about the canali of Mars and inspired Percival Lowell to found his observatory—showed that their orbits matched.
While the magnificent display of the Perseids has inspired many people through the years, one of particular note is Deutschendorf, who was on camping trip in Colorado at the time. He recalled his experience years later in his autobiography:
We were right below the tree line, just about ten thousand feet, and we hadn’t seen too much (Perseid meteor) activity in the sky yet. There was a stand of trees over by the lake, and about a dozen aspens scattered around. Around midnight, I had to get up to pee and stepped out into this open spot. It was dark over by those trees, darker than in the clearing. I looked over there and could see the shadow from the starlight. There was so much light from the stars in the sky that there was a noticeable difference between the clearing and everywhere else. The shadow of the starlight blew me away… I went back and lay down… thinking about how in nature all things, large and small, were interwoven, when swoosh, a meteor went smoking by. And from all over the campground came the awed responses “Do you see that?” It got bigger and bigger until the tail stretched out all the way across the sky and burned itself out. Everybody was awake, and it was raining fire in the sky.
Deutschendorf’s stage name was John Denver, and this experience with the Perseids stirred him to write his now-classic song, Rocky Mountain High.