The Geminid meteor shower is now active and will reach maximum activity on Saturday evening/Sunday morning December 13/14. Activity is currently low with less than 5 meteors per hour appearing from this source. Rates are usually twice this number but the nearly full moon obscures all but the brightest meteors. Activity will increase each night until maximum activity is reached on the 13/14. After maximum, rates will fall swiftly and Geminid meteors will soon disappear.
On the night of December 13/14, Geminid meteors will appear as soon as becomes dark. Activity will be low but the meteors you see will be long and long-lasting. They will shoot from the northeastern horizon in all directions. Most of them will hug the north or southeastern horizon. Occasionally you will see one shooting straight up and these will be a real treat.
As the night progresses the Geminid meteors will become shorter and will move in all directions, including downward toward the eastern horizon. Activity will also increase as the Geminid radiant (the area of the sky Geminid meteors appear to shoot from) climbs higher into the eastern sky. Near 10pm local standard time (LST), the Geminid radiant will lie approximately half-way up in the eastern sky. At this time viewers from the city can expect to see 10-20 Geminids per hour. If you live in the suburbs then hourly rates should be 20-30 Geminids per hour. If you live in rural areas then hourly rates should be 30-40 Geminids per hour. The reason for this difference is that most of the Geminid meteors are faint. Faint meteors, just like faint stars, are obscured by city lights. The darker your environment, the more meteors you will see.
Geminid activity will continue to increase until around midnight, when the half-illuminated moon rises in the east. Rates near 60 Geminid meteors should be seen between midnight and 2am from rural locations. After that, the Geminid radiant begins to set in the western sky and the moon gains altitude in the east. Geminid rates will then begin to fall due to the increased intensity of the moonlight and the declining horizon distance. Geminid meteors, like all shower meteors, will appear in “clumps”. One may see nothing for 5 minutes and then see 5 meteors within the next minute. This is why it is important that observers watch for as long as possible. If you watch for a short time you may be watching during a slump in activity and will be disappointed.
Not all meteors seen this time of year are Geminids. There are other minor showers active which are both faster and slower than the Geminids. There are also random meteors not associated with any known shower. Roughly 80% of the meteors should be Geminids on December 13/14. This percentage will be less on nights away from maximum. Geminid meteors are of medium speed and their average duration is on the order of a half-second. Brighter Geminids will last longer and Geminid fireballs can last several seconds and exhibit brilliant colors such as orange and green.
I would advise potential viewers not the wait until December 13/14, just in case this night is cloudy. The night of December 11/12 is good and the 12/13th is almost as good as the night of maximum activity. Rates will fall by at least 50% each night after maximum.
Viewers all over the world can see this display of meteors. The only continent where the display is invisible is Antarctica. From there the radiant never rises above the horizon plus daylight lasts 24 hours this time of year. Viewers in the northern hemisphere have a distinct advantage as the nights are longer plus the Geminid radiant rises higher into the sky. Observers in Australia, southern Africa, and South America can best see Geminid activity near 0200 LST or 0300 local daylight saving time, when the radiant lies highest in their northern sky.
I will be happy to answer any questions you have concerning the Geminids. Before you ask please note that these meteors can be seen from anywhere north of Antarctica and that the best time to watch is between 10pm and 2am local standard time, no matter your location.
American Meteor Society