Here Come the Geminids

Geminids - Asteroidal debris rains down on Earth during the Geminid meteor shower 2014.


Photographer Neil Zeller made this spectacular composite last year, northeast of Calgary, in Canada, capturing the Milky Way, several Geminids, and a beautiful green aurora on the horizon. All the meteors come from the same direction, because they’re part of the Gemini system. There could have been an occasional meteor not of this system and coming from a different direction, but not in this picture.

They come from the direction of the Gemini constellation (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 all come from the same spot ahead of you and streak past you on the sides.

The annual Geminid meteor shower lasts several days, but is only visible at night (barring something unusual and spectacular, of course.) Tonight, Sunday, December 13, and early tomorrow morning, the shower will be at its most intense.

A meteor shower happens when Earth moves through a trail of debris left behind by a comet, usually. The Geminids are the only known exception, being debris in the orbit of an asteroid. Asteroid 3200 Phaethon, to be specific.

In Phaethon’s long elliptical orbit around the sun (shown below), it almost falls into the sun from way out near Jupiter’s orbit. It scrapes past the sun far below the orbit of Mercury and gets so close to the sun that bits of it vaporize and blow pieces of rock off. Each little shard moves as fast as 40 kilometers/sec (or 86,000 mph). This is fast enough that, as a few of them scream through our atmosphere, they heat up instantly and glow. We see them as blazing streaks of light and call them “shooting stars.”

Orbit of the dead comet:asteroid 3200 Phaethon

This year will be exceptionally good, because the Moon will be new and won’t wash out the night sky. This will make fainter meteors easier to see.

Watching a meteor shower is pretty easy. Basically, all you have to do is go outside, look up, and be patient. Shooting stars are largely random, so you might not see any for a while. Then you’ll see several in a row. The important thing is to be patient. Any time after about 10 p.m. local time should be fine, but you’ll see the most after midnight. That’s when the Earth will be facing into the oncoming meteor stream.

Some general notes for viewing Geminids

  • It takes about 20 minutes for your eyes to get adapted to the dark; longer for an older person. So you may see few meteors right away. Or even none.
  • Make sure street lights are blocked and your house lights are off.
  • White light from a flashlight, street light, car, or window of a house will wipe out your night vision all over again for another 20 minutes. Be prepared with a flashlight with red cellophane covering the lens in case you need light. This will preserve your night vision. Or using a red flashlight app on your smartphone ought to work.
  • Avoid nearby buildings or trees that will block your view of the sky.
  • Make sure you’ll be warm and comfortable.
  • No telescope or binoculars needed. Just use your eyes.

About 1:00 a.m., Jupiter will rise in the east and provide an additional treat.

Slate’s “Bad Astronomer,” Phil Plait, says this:

Asteroids orbit the Sun for billions of years, and you’re seeing tiny parts of them—most no bigger than a grain of sand—as they slam into our atmosphere a hundred kilometers (60 miles) above you at speeds of up to 40 kilometers per second (86,000 mph). How cool is that?

He adds that the most important things to remember are your joy and wonder.

Joy and Wonder

These may be the best things to bring, and the easiest. Meteor showers are simply wonderful. It’s a cosmic show, and IT’S FREE, and it’s very, very cool.

I agree.


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