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Jump out of bed for the Geminids

Starwatch

Stargazing will be worth losing sleep over this week as you bundle up to enjoy the annual Geminid meteor shower, one of the best of the year.

It reaches its peak very late this coming Wednesday night into Thursday morning, Dec. 13 to 14.

Meteor showers occur when the Earth runs into a debris trail of dust and small pebbles as it orbits around the sun. Most debris trails are left behind by passing comets that wander into our part of the solar system.

The Geminids are unusual because the debris trail was left behind by a messy asteroid dubbed by astronomers as 3200 Phaethon. This asteroid was discovered in 1983 and may have a diameter of around 3½ miles. 3200 Phaethon is a real cosmic litterbug! That’s unusual for an asteroid. It has a highly elliptical orbit that swings it by our part of the solar system every year and a half. Each time it passes by, the debris trail is richly refreshed.

All meteor showers are best seen from midnight to morning twilight, especially about two to three hours before twilight. That’s because our part of the Earth has rotated into the direction of Earth’s orbit and the debris trail.

A good analogy is driving on a warm summer evening; many more bugs are meeting their demise on your front windshield than on your rear window. After midnight, we’re facing the “front windshield.” The Geminids will be especially good this year because the moon sets well before midnight, giving us darker skies.

On Thursday morning during the peak of the Geminids, try to get away from bright city lights into the darker countryside if you don’t already live there. You may see over 50 to 100 meteors in dark, rural areas an hour. Even if you’re stuck with more lit-up urban skies, you can see 20 to 30 “shooting stars” an hour if you’re a keen observer.

Some of these meteors are slamming into our atmosphere at over 40 miles a second. These bits of dust and pebbles get incinerated and vaporized anywhere from 40 to 60 miles above our heads.

There’s no way you could see the combustion of tiny debris that high up. The light you see results from tiny columns of air becoming temporarily destabilized and excited as the debris slams through. Electrons from the atoms get bounced away and then quickly return to their stable orbit.

These streaks can often stay visible for a second or two after the meteor passes while the column of air gets its act back together. Meteors can and do sport different colors depending on what kind of gases they run into, how large, and how fast they’re moving. In general, the reddish-tinged meteors tend to be slower, and quicker meteors are more bluish.

This shower is called the Geminid meteor shower because all the meteors appear to be coming from the general direction of the constellation Gemini the Twins, which is in the early morning Western sky.

However, you should not restrict your viewing to that part of the sky because the meteors will be all over the heavens, and I don’t want you to miss any.

The best thing to do is to layer up in clothes, coats and blankets and lie back on a fully reclining lawn chair, rolling your eyes all around and keeping count of how many meteors you see. Above all, be patient and vigilant. Meteor shower watching is especially fun with a group of people because the more sets of eyes you have scanning the sky, the more meteors you’ll see collectively.

While you’re lying out watching for meteors, think about this: 3200 Phaethon could be a potential killer asteroid and wipe out most life on Earth if it hit us at just the correct angle. It’s not expected to do that in the foreseeable future, but in 2093 it will miss the Earth by less than 2 million miles. Circle that on your calendar!

Happy Geminid watching!

Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of "Stars: a Month by Month Tour of the Constellations," published by Adventure Publications and available at bookstores and adventurepublications.net. Contact him at mikewlynch@comcast.net.

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