The Geminid Meteor Shower

The Geminid meteor shower, commonly called the Geminids, is a yearly meteor shower seen from the Earth in December. It is named after the constellation Gemini where the radiant, the point from where the meteors seem to come from, is located. The Geminids are active every year from about December 6 to December 19 with the most active period at December 13 and 14.

The maximum rate, or the number of meteors that fall per hour when the shower is at its heaviest, has increased every year since the discovery of the Geminids in 1862. In 1877 the maximum rate was 15 meteors per hour, in the 1890s maximum rates reached 25 meteors per hour, and by the 1990s maximum rates were more than 80 meteors per hour.  Recent showers have seen 120-160 meteors per hour.

The meteors from the Geminids travel in relatively medium speed compared to other showers at about 35 kilometers per second making them fairly easy to spot. The meteors often appear yellowish in hue and disintegrate at heights above 38 kilometers.

This 2012, the maximum rate is predicted to be at around 120 per hour though on average it produces 50 or more meteors per hour. The new moon falls on December 13 ensuring dark nights for viewing the Geminids. The best place to view the Geminids is under a wide dark sky. It would be better if you let your eyes adapt to the darkness to better view the meteors. The Geminid radiant point lies close to the star Castor and would climb above the eastern horizon at about 7 pm. The greatest number of meteors fall at around 1 to 2 am when the radiant point is highest in the sky.

The Geminids were discovered by English and American observers in 1862. In 1947 Czechoslovakian astronomer Miroslav Plavec first determined the orbit of the stream of meteors that causes the shower He noted that the gravitational force of the planet Jupiter was causing the orbit to shift its position gradually. The earth first passed through the Geminid meteor stream in the 19th century, and the meteor stream will probably move out of the earth’s path after the 21st century.
The Geminid meteor shower is the only meteor showers to be linked to an asteroid. The parent object of the Geminid shower, 3200 Phaethon, was discovered and photographed in 1983 by the Infrared Astronomical Satellite and has the appearances of a small Earth-crossing asteroid. This object does not exhibit the usual features of a comet such as the nebulous head and long tail and so was place among the asteroids. Most researchers believe that Phaethon is the burned-out remnant of a once-active comet.

 
Prepared by Peter Singer Jr.

References:
"Geminids." Microsoft® Encarta® 2009 [DVD]. Redmond, WA: Microsoft Corporation, 2008.
"meteor and meteoroid." Encyclopædia Britannica. Encyclopædia Britannica Ultimate Reference Suite.  Chicago: Encyclopædia Britannica, 2011.
http://en.wikipedia.org/wiki/Geminids retrieved on 12/12/2012http://earthsky.org/astronomy-essentials/ten-tips-for-watching-the-geminid-meteor-shower retrieved on 12/12/2012