Dr S A Mohan Krishna

Mysuru: December, January and February of any year shall be best remembered as the months meant for sky watching. Among all sky events, the best remembered is a ‘meteor’ or a ‘shooting star’.

A ‘shooting star’ or ‘meteor’ is caused by a tiny particle of dust entering 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. It is an exceptional celestial manifestation for sky observers that the extravagant yearly ‘Geminid’ showers will illuminate the night sky on December 13 and 14.

The Geminids are beautiful, prolific and reliable shower. On December 13 and 14, Indians are really fortunate to witness the dazzling Geminid meteor showers. Geminids 2020 was one of the best meteor showers which are still memorable.

Dry, clear air will help a lot with the lunar glare, but it will be difficult to achieve maximum rates of 60 to 120. During those hours, we may be able to put it behind and out of your field of view. Geminids are medium-speed meteors. The shower has a skew rate profile, with activity dropping speedily after maximum. At the same time, the proportion of bright meteors is higher during and after maximum than on pre-maximum nights. The Geminids are worth watching for one or two mornings before the peak; there will be slightly less moonlight interference, and some locations will get a short moonless period before morning twilight. 

The Geminids should produce a fine display of 1-2 meteor every minute for North American observers with dark skies, weather permitting. Brief bursts of activity could produce even higher rates. The nights and mornings surrounding the peak activity should prove rewarding, too. 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 still see a very good meteor display on the night of Dec. 13-14, with rates of about one meteor per minute likely. This time in India Geminids are clearly visible in the night sky during 10 pm to 6 am. 

The Geminid display is for those willing to brave the chill of a December night a fine winter shower, and usually the most satisfying of all the annual showers, even surpassing the more widely recognized Perseids of August. Studies illustrate that the Geminids are rich in slow, bright, graceful meteors and bright fireballs, as well as faint meteors, with relatively fewer objects of medium brightness. Geminid meteors are several times denser than the cometary dust flakes that supply most meteor showers, so they burn up less quickly. But for the visibility of Geminid Meteor Shower, there is absolutely no difficulty at all. The night sky is completely free from moon and eventually may be possible to witness these meteor streaks.  Peak activity is projected to fortuitously occur at or near 3 to 4 a.m. IST on Dec. 14. 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 the average.

During the early morning hours of December 14 the peak rate for the 2021 Geminid meteor shower is predicted to be as high as 80 to 130 meteors per hour. That works out to about one meteor every 30 seconds. If the predictions are right, it should be a great show. The best time to observe meteors is between midnight and dawn. The Geminid meteor shower is no exception, so the first step is to either stay up late or get up very early to observe the sky between midnight and dawn. There will be moonlight to interfere with observing meteors. The Geminid shower peaks on the early morning of December 14, so that is the best night to go out to observe them.

To see maximum number of meteors, go to a dark sky as far away from lights as reasonably possible. Allow time for your eyes to become dark adapted. Use a red flashlight for light to preserve your night vision. Red fingernail 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 other optical device is needed. In fact telescopes or binoculars will limit stargazers field of view making it nearly impossible to observe meteors.

The Geminids have a fairly broad maximum, so viewing should be productive throughout the entire night of December 13/14. The Geminids are accessible from the entire Northern Hemisphere and from many Southern Hemisphere locations as well. The radiant 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. The Geminids can produce observed rates of over 100/hour at maximum, and are reliable as well as spectacular.

A productive Geminid watch can actually begin as early as 8 p.m. local time, because the showers radiant is already fairly high in the eastern sky by then. The Geminids will be especially noticeable right after the Moonsets, as their radiant point will be passing very 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 less than half the width of the Moon. As such, this is a rather sharply defined radiant, as meteor showers go, suggesting 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 Earths 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.

( The writer is amateur astronomer and Convener, Mysore, Astronomical Society)

– Team  Mysoorunews                             

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