Geminid showers all set to dazzle

Skywatch

It is that time of the year when the Geminid meteor showers will treat us with their glowing presence. Gear up, says S A Mohan Krishna.

In an exceptional celestial manifestation for sky observers, the Geminid showers will illuminate the night sky on December 13 and 14. These beautiful and prolific meteor showers are an yearly occurrence.

A ‘shooting star’ or ‘meteor’ is caused by a tiny particle of dust entering the Earth’s atmosphere. As it plunges downward, it experiences collision with air molecules, and the friction generated causes the particle to glow and eventually burn up completely. Most meteors burn up at altitudes of around 100 km.

Geminids are medium-speed meteors. This meteor shower in usually seen in the Gemini constellation depicting the two stars — Castor and Pollux. The Geminids should produce a fine display of 1-2 meteors every minute for North American observers with dark skies, weather permitting.

In other parts of the world, such as Europe, Asia and Australia, the Geminid peak will come during local daylight hours. Still, observers in these parts of the world should be able to see a very good meteor display on the night of December 13 and 14, with rates of about one meteor per minute.
This time, in India, Geminids will be clearly visible in the night sky from 2 am to 4 am. A bright waxing gibbous moon may interfere during peak night and it is always advisable to witness after moonset.

Peak activity

If predictions are right, it should be a great show. The best time to watch it is between midnight and dawn. Peak activity is projected to fortuitously occur at or near 4 am IST on December 14 and this is the best night to go out to observe them. Under normal conditions, on the night of maximum activity, with ideal dark-sky conditions, at least 60 to 120 Geminid meteors can be expected to burst across the sky every hour, on an average.

During the early morning hours of December 14, the peak rate for the 2013 Geminid meteor shower is predicted to be as high as 120 meteors per hour. That works out to about one meteor every 30 seconds.

The dazzling display is for those willing to brave the chill of a December night for a fine winter shower. It is usually more satisfying than all the annual showers, surpassing even the more widely recognised Perseids of August.

To see the maximum number of meteors, go to a dark sky as far away from lights as reasonably possible. Allow time for your eyes to adapt to the dark. Use a red flashlight for light, to preserve your night vision. Red nail polish works for making an astronomical flashlight.

Look up in the sky in the direction of the constellation Gemini. Stargazers who don’t know the constellation Gemini can look in the eastern half of the sky. No telescope or optical device is needed. In fact, telescopes or binoculars will limit the field of view of the stargazers, making it nearly impossible to observe meteors.

Productive watch

The Geminids have a fairly broad maximum, so viewing should be productive throughout both the nights. The Geminids are accessible from the entire Northern Hemisphere and from many Southern Hemisphere locations as well.

The radiance is highest in the sky at around 2 am, but, from mid-northern latitudes, it is at a decent elevation from around 10 pm, until the beginning of morning twilight.

A productive Geminid watch can actually begin as early as 10 pm local time because the showers’ radiance is already fairly high in the eastern sky by then. The Geminids will be especially noticeable right after the moon sets, as their radiant point will be passing nearly overhead. The higher a showers’ radiant, the more meteors it produces all over the sky.

The track of each one does not necessarily begin near Castor, nor even in the constellation Gemini, but it always turns out that the path of a Geminid, extended backward along the direction of flight, passes through a tiny region of sky about 0.2 in diameter. In apparent size, that is less than half the width of the Moon.

As such, this is a rather sharply defined radiant, as meteor showers go, suggesting that the stream of space debris, that fuels this shower, is relatively young, perhaps only several thousand years old.
Geminids stand apart from the other meteor showers in that they seem to have been spawned not by a comet, but by 3200 Phaeton, an asteroid that crosses the path of the Earth’s orbit.

Then again, the Geminids may be comet debris after all, for some astronomers consider Phaeton to really be the dead nucleus of a burned-out comet that somehow got trapped into an unusually tight orbit around the Sun.