The Leonid meteor shower peaks today. Its parent comet taught us where meteor showers come from.
Every year, as Earth regularly orbits the Sun, meteor showers repeatedly recur.
August’s Perseids and December’s Geminids are annually spectacular, but November’s Leonids have more astronomical importance.
In contrast to their typically modest show, the Leonid display is spectacular every 33¼ years.
In 1833, the Leonids caused a meteor storm worldwide, producing 1,000+ meteors-per-hour.
For each of the next 32 years, they were quiet, but then exploded once again in 1866.
British Astronomer John Couch Adams, famous for almost (but not quite) discovering Neptune, had a three-part idea.
1.) What we observe as “shooting stars” or meteors are small, fast-moving dust grains burning up in our atmosphere.
2.) Meteor showers recur annually when Earth passes through each dusty debris stream.
3.) Every debris stream is spread-out, but has a point of maximum density, corresponding to meteor storms.
His idea was speculative, but provable, assuming he could find the parent body.
His experience calculating orbits while searching for Neptune proved indispensible, deriving a Uranus-crossing, 33¼ year orbit for the Leonids.
It matched the newly discovered Comet Tempel-Tuttle almost exactly, ushering in the meteor shower-comet connection.
The Leonids peak tonight, marking 153 years of humanity knowing the cause of these celestial fireworks.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.