A Rain of (Teeny) Asteroids

Over the weekend, the Geminid meteor shower came to a peak. This annual event occurs when the Earth plows through debris left behind by the asteroid 3200 Phaethon as it orbits the Sun (it gets so close to the Sun that bits of the rock vaporize and blow off the asteroid). Each little bit of interplanetary detritus is moving at about 35 kilometers/sec (22 miles/sec), fast enough that as it rams through our air, it heats up enough to become incandescent, and we see a “shooting star.”

I was out Saturday night (Dec. 13), and over the course of two hours I saw so many I lost count; I’m pretty sure I spotted at least 80. I wasn’t able to get any Geminids on camera (grrrrr), but happily photographer Neil Zeller had far better results:

Spectacular! He drove up northeast of Calgary to get nice dark skies, and it was clearly worth the trip. The photo is actually a composite of several exposures; he was facing northwest and captured the Milky Way, several Geminids, and a lovely green aurora on the horizon (Zeller has an astonishing gallery of aurora photos on his website). On the far right you can just see an interesting pair of stars tightly spaced; that’s Mizar and Alcor, the stars in the bend in the Big Dipper’s handle.

As you can see, all the meteors seem to point in the same direction. That’s because they do! The meteors appear to come from a part of the sky near the head of Gemini (hence their name), and radiate away from that point in all directions. It’s a perspective effect, like driving through a tunnel and seeing the lights on the walls appear to come from the same spot ahead of you, and streak away to the sides.

As I stood under the chilly Colorado sky Saturday, this radiating effect was pretty strong; I saw meteors in any part of the sky I looked, and they always pointed back toward Gemini (except for one that was a random meteor unrelated to the shower; on any night you can usually see a few per hour). I saw every flavor of meteor, too: long streaks, short ones, faint ones, bright ones, and one that flared about as bright as Jupiter (magnitude -1 or 2 if you want details) that left a luminous vapor trail that lasted for just a second or two. That was amazing.

This was easily the best meteor shower I’ve ever watched myself. It’s usually too cold and cloudy this time of year to see it, but things worked out well; in fact, as I write this (the day after the shower) it’s snowing!

And I did get a lot of very pretty pictures from the night, including this one of Orion through the trees (and Sirius, the brightest star of the night sky, to the lower left). It was totally worth the cold fingers, toes, and nose.

Tip o' the lens cap to Daggerville on Twitter.