Perseid shooting stars: a journey billions of miles and thousands of years in the making

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Picture it: A slash of vivid green light splits the starry sky. There for a moment and then gone, leaving nothing but a short-lived glowing trail and a moment of pure joy. You've finally caught it, your first Perseid shooting star of the season.

What you saw was the final moment of a story billions of miles and thousands of years in the making. A story that began with that same shooting star locked inside the icy body of the wandering comet 109P/Swift-Tuttle.

The 16-mile-wide (26 kilometer) giant of a comet spends its life journeying back and forth between the outer and inner solar system, where its frigid body is heated by the sun , triggering dramatic outbursts of activity. While in close proximity to our star, ice near to the surface of the comet is transformed into gas, skipping the water stage entirely as it escapes out into the vastness of interplanetary space.

Embedded within that ice was once a micrometeoroid no larger than a grain of sand, destined to become the Perseid shooting star you saw.

The violence of the newborn micrometeoroid's exile was followed by an epoch of utter silence, as its orbit was subtly influenced by the unseen forces of the solar system . It would be easy to think of this as a lonely existence, but we'd be wrong.

Our cosmic pebble was joined by millions of others, all shed in the wake of Swift-Tuttle. A great stream of primordial material that threads through the inner solar system, crossing the path of Earth before extending in a great swarm that messily traces the elliptical orbit of their comet progenitor, below the plane of the solar system. Beyond the orbit of Pluto .

Each follows its own unique path. Trajectories are shaped by the force of a micrometeoroid's expulsion from the comet's nucleus, along with the gentle push of radiation from the sun and the gravitational tug of the planets.

A perseid blazes earthward over Hubei province in China. (Image credit: Photo credit should read CFOTO/Future Publishing via Getty Images)) It's impossible to know how long our shooting star drifted through the cold expanse of interplanetary space. Was it hundreds or many thousands of years? How many times might it have journeyed around the sun before its fateful rendezvous with our Blue Marble?

We can never know. What we do know is how its journey ended.

Civilizations could have risen to their zenith and crumbled in the time our micrometeoroid spent traversing the unfeeling expanse of interplanetary space, but its demise lasted but a fraction of a second. It collided with our planet's gaseous shell at 132,000 miles per hour (212,433 kmph), cutting a brilliant green trail through the summer sky as atmospheric friction vaporized the cometary shard.

It's that fiery demise that you spotted tonight — an experience that will repeat hundreds of times each and every hour at the height of the Perseid meteor shower, as Earth passes through the densest part of the debris stream cast off by comet Swift-Tuttle .

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The Perseid meteor shower is active from now until Aug. 24, with the best viewing window occurring in the early hours of Aug. 13, as the shower's radiant rises to its highest point on the night of the shower's peak.

This year's peak will be particularly spectacular, unfolding as it does in the pristinely dark skies surrounding the Aug. 12 new moon , which will also cause a spectacular total solar eclipse to be visible across parts of Spain, Iceland and Greenland. If you find yourself in the path of totality and have luck on your side, then you might just spot a Perseid fireball brightening the false twilight that falls as the moon hides the face of the sun at the crescendo of the eclipse!

Want to capture a shooting star that will stay with you forever? Then be sure to read our guide to photographing fast-moving meteors , along with our roundups of the best cameras and lenses for astrophotography if you're looking to upgrade your gear.

Editor's Note: Did you catch a photo of a Perseid shooting star and want to share it with Space.com's readers? Then please go ahead and send your photos along with your comments, name and location to spacephotos@space.com.