- December 10, 2015 - Planétarium Rio Tinto Alcan : Astronomical News
Of all the annual meteor showers, the Geminids are among the most reliable and prolific. Each year at their peak, on December 14, they produce a maximum of 120 meteors per hour – even more than the famous August Perseids!
Some background facts
While most meteor showers are fuelled by comet dust, the Geminids are the only one whose source is an asteroid: 3200 Phaethon. Each year around mid-December, Earth grazes the orbit of Phaethon, which leaves billions of particles in its wake, giving rise to this renown meteor shower. The recent discovery that some asteroids are conglomerations of loosely packed rock, helps to explain how an asteroid could produce all the dust necessary for a meteor shower. Phaethon orbits the Sun once every 523 days, constantly replenishing the Geminid meteor stream, making it one of the most prolific showers of the year.
The Geminids in detail
When meteoroids enter the atmosphere, they create tubes of ionized air which leave glowing trails—shooting stars. The Geminids have an average velocity of 36 km/sec, about half that of the Perseids, which gives them a yellowish colour. The radiant, the part of the sky where the meteors appear to emanate, is located in the constellation of Gemini, near the bright stars Castor and Pollux. In fact, shooting stars can also be seen all over the sky, but if they are Geminids their trails will all point back toward the radiant.
This year, the Geminids reach their maximum around 1:00 P.M. (EST) on December 14, so one can expect a very nice show on the nights of the 13th to 14th and 14th to 15th. One might also consider observing the meteors on the preceding and following evenings, though they will be less abundant. This year astronomical conditions are excellent: the crescent moon will not hinder observations since it will set early in the evening.
How to observe the Geminids
As twilight ends, let your eyes wander across the sky. If you are in a group, position yourselves so everyone faces a different direction... and be prepared for a few surprizes! Under a dark country sky, one should expect to see between 60 and 80 meteors an hour.
So… the rest is up to you: Head out of the city, away from light pollution; bring a lawn chair, blankets and a thermos of hot chocolate; and above all—dress warmly! Then settle back, scan the sky with your eyes (binoculars won’t help) and begin counting meteors…