Friday, December 4, 2009

Geminid Meteor Shower December 13-14

Posted by Kirk Mona
The Geminid Meteor Shower will be visible this month in the Twin Cities (the rest of the world as well.) The general "peak" of activity is considered to be on December 13, 11:10 pm central standard time. The good news is that the peak is early so you don't have to be up in the wee hours. The radiant of the shower in the constellation Gemini will be about 50° up in the sky at 11:00 which isn't too shabby so we should see some good action. The closer to the zenith (90° or straight up) the more meteors we see. The "peak" or time of greatest intensity of the shower is actually fairly wide so viewing should be good all night. There is some reason to hope that the Geminids may peak out at up to 120 to 150 meteors per hour this year! Keep in mind though that it will be hard to actually see this many unless you can get ery far awya from city lights. The Moon will be a complete non-factor. Not only will it be only a slim crescent at the time it will also be well below the horizon. The meteors all seem to radiate from the direction of Gemini but they can be heading in any direction from there do you don't need to stare in any particular direction.

The Geminids are a fascinating meteor shower as they are relatively new. They have been increasing over the decades from when they were first discovered. The shower has only been known for the last 150 years. I know I always think of meteor showers as stretching back to antiquity so this is fascinating. Most meteor showers are caused by active periodic comets that circle the sun and leave behind dust trails. The planet intersects these dust lanes and we see "shooting stars" as the particles burn up in our atmosphere. Aside from being new, another reason the Gemenids are interesting is that they are not caused by a comet but rather a strange asteroid called 3200 Phaethon. The source of the Gemenids was a mystery until Phaethon was discovered in 1983. Phaethon has an orbit that takes to from near Mars to extremely close to the Sun. It comes as close to the sun as half the distance from the Sun to Mercury. Phaethon's orbit is slowly changing which is why the shower is becoming more intense. After some time around 2100 the orbit will have changed enough that this meteor shower will have disappeared.

People have asked me where the best place is to view meteor showers in the Twin Cities metro area. That's a tough question. It all depends on how many you want to see. I've seen plenty of meteors from my light polluted St. Paul back yard. Shield your eyes from any stray light such as street lamps and turn the lights off in your house. Most of all, let your eyes adjust to the dark. Fifteen to thirty minutes of letting your eyes adjust to the dark will let you see many many more meteors.

Suppose you want to drive a little though to get a good view? Since my last posting about the Leonid meteor shower earlier this year, I've since discovered a wonderful resource for finding the darkest sky near your location. Check out this wonderful interactive map.

If you look at the map and center in on the Twin Cities of Minneapolis and St. Paul, you can see light pollution is pretty bad anywhere near the metro. What direction to travel depends a little on where in the metro you live. Heading out to an area in the yellow zone on the map will at least give you somewhat darker skies. You need a minimum of a two hour drive to get to a truly dark site and likely it will take even longer. Think boundary waters for true darkness! At any rate, you can most likely easily see a few good "shooting stars." from your own back yard.

The Geminids are beautiful but come at a cold time of the year. Dress warm and post a message in the comments if you see anything good!

~Kirk

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