Written by Emily Brodsky
The alarm went off at 3 AM. I lay on the cabin floor, my breath visible in the cold night air. The fire, which had been blazing at bedtime, by now had dampened to a few glowing embers. Imagining the dazzling show that awaited me outside, I resisted the temptation to return to my warm and peaceful slumber. Instead, I emerged from my puffy cocoon, and tiptoed about the cabin to rouse the adventurous souls who had committed to my pre-dawn wake-up call. Groggily, we donned our winter coats and hats, and dragged our sleeping bags into the chill of a mid-November night. We were on a mission to observe one of the universe’s great spectacles: the annual Leonids Meteor Shower.
After stumbling down a dark, wooded path, we planted ourselves in an open field and eagerly fixed our eyes on the sky. The stars were shrouded by stratus clouds. We waited.
After half an hour or so, the clouds parted and revealed one of the most awe-inspiring sights I’ve ever witnessed. For several hours, sparkling streams of light rushed over our heads in all directions. They varied in color from white to blue to yellow, and I don’t know if I imagined it, but I swore I could hear them zooming through the sky. The show went on until the meteors were outshined by the light of dawn. After the final stragglers passed overhead and the darkness began to lift, my friends and I clapped and cheered. We had witnessed not just a meteor shower, but the great meteor storm of 2001.
Thanksgiving-time brings well-stocked dinner tables, family and friends, and cozy, tryptophan-induced naps. A less-known fact is that it also brings meteors. Just before the holiday rolls around each year, one can stumble into the out-of-doors in the dead of night to watch these glittering speed demons as they race across the sky. How do the Leonids put on their marvelous show, and why does it happen with such consistency?
The orbit of the comet Tempel-Tuttle happens to intersect with Earth’s, and when the comet passes by every 33 years it leaves a dense trail of debris. As the Earth passes through the lingering dust cloud each November, thousands of particles crash into the atmosphere. These sand grain to pebble sized particles, called meteoroids, travel through space at speeds up to 162,000 miles per hour. Space is a vacuum, meaning matter is scarce; thus, nothing slows the meteoroids as they speed through the galaxy — that is, until they collide with the matter-laden atmosphere of Earth.
When meteoroids strike, they push up against the gaseous molecules of the atmosphere with incredible force. The astronomical equivalent of a 10-car pileup occurs, with molecules squishing together in front of each meteoroid, and the resulting pressure generates so much heat that the meteoroids reach boiling point. The meteoroids continue to move through the atmosphere, vaporizing layer by layer and releasing a tremendous amount of heat. As the heat releases, the meteoroids and surrounding molecules glow. From our vantage point 50-75 miles below, these hot, disintegrating particles appear as the streams of light we call meteors, or shooting stars.
The Tempel-Tuttle dust cloud is one of several that Earth passes through consistently. The predictable display produced by this annual event is called the Leonids because its radiant, or the point from which the meteors appear to radiate, is the constellation Leo. Other meteor showers include the Geminids in December, the Lyrids in April, and the Perseids in August — their radiants being Gemini, Lyra, and Perseus, respectively.
Although the Leonids have been known to cascade over the sky in numbers up to one-hundred-thousand or more per hour, typical displays are not so prolific. The last exceptional shows (known as meteor “storms”) were in 2001 and 2002, with meteors-per-hour estimates of up to 3,000. More commonly, the Leonids shower produces 10-15 meteors per hour. The numbers depend on a variety of factors, including solar wind and dust cloud density. Visibility depends on cloud cover and the moon phase. To see the Leonids in their full splendor, conditions must be just right.
Sadly, the last-quarter moon will be shining near Leo during this year’s November 17-18th peak, resulting in low visibility and a relatively weak show. Still, I plan to look. Since that wonderful night in 2001, I have lain in various fields and hiked up mountains to observe the Leonids. Every year, they seem to be blocked by clouds. I’ve never been disappointed, however, as the experience of watching celestial events like meteor showers goes beyond the objects themselves; it’s also about the adventure of being outside at an ungodly hour, enduring sleepiness and cold, and sharing an unusual moment with friends. I encourage you to go out in the wee hours of November 18th; whether you’ll see a shooting star, I cannot guarantee, but I can assure you that the excursion will make you feel alive.