Celestial Fireworks

        Many of the times, when you are looking at the star-studded night sky, suddenly you see a beautiful light streak across it. In common terms, this event is termed as a 'shooting star'. Astronomers call it a meteor. There are certain nights of the year when such meteors are seen in large numbers, these events are known as a 'meteor shower'.

        Every year, after the celebration of Diwali (a festival of light, celebrated across India) with lights and fireworks, you may get a chance to see such a celestial fireworks in the sky on certain nights. One of these is the night of December 13-14. This is the night when Geminid is active. Meteor showers can be observed with unaided eyes, without any need of a telescope. To have more fun observing, let us understand a little bit about the meteor showers.

        What we call a shooting star is actually dust particle in space. When a dust particle from space enters the earth's atmosphere, it gets ignited due to the friction with the air and you see a streak of light as if the star is suddenly falling. This is a meteor.

Where do these dust particles come from in space?

        These dust particles are mostly the particles left behind from comets. There may also be fragments of asteroids. The size of these remains of comets and asteroids can range from a few micrometers to a few meters.

        Comets usually come from the outer region of our solar system, from the space beyond Neptune. As the heat from the sun is not so intense over long distances, comets are frozen bodies. As a comet moves closer to the Sun it in its orbit around it, it starts vaporizing due to solar wind and heat. The ionized gas molecules and dust particle thus separated from the comet are thrown in the opposite direction to the Sun. These are what make the tails of a comet. As the comet travels further, the separated remnants are left behind it in its orbit.

How do these remnants enter the Earth?

    The Earth while revolving around the Sun sometimes passes through this space debris left by the comet. Some of these particles enter the Earth's atmosphere, get burnt due to friction with the atmosphere, and you see meteors. If you observe clear skies from a dark place with negligible light pollution, at any time of the night you have fair chances to witness such sudden meteors.

Why do meteors appear more frequently on certain nights?

        Some comets, as well as asteroids, have a higher density of the debris left behind. If the Earth travels through this band of the debris, a large number of these dust particles enter the atmosphere and more meteors are seen that night. This is what we call a meteor shower.

          If you observe carefully on the meteor shower nights, you will find most of these meteors appear to come from a certain point in the sky. This virtual point is called the radiant. The meteor shower is named after the constellation in which this radiant appears to be. For example, Geminid meteor shower that occurs in the month of December is named ‘Geminid’ because its radiant lies in the constellation Gemini.

 The following table summarizes some of the famous meteor showers.

Meteor Shower	Period	Active on	Hourly rate	Parent Body
Quadrantid	January 01 - 05	January 03	120	Asteroid 2003 EH1
Lyrid	April 25 - 28	April 22	15	Comet Thatcher
Eta Aquarid	April 19 - May 28	May 06	60	Halley's Comet
Arietid	May 22 - July 02	June 07	54	Machholtz Comet
Delta Aquarid	July 12 - August 19	July 28	20	Machholtz Comet
Perseid	July 17 - August 24	August 12	90	Comet Swift - Tuttle
Orionid	October 02 - November 17	October 21	20	Halley's Comet
Leonid	November 06 – 30	December 17	15	Comet Tempel - Tuttle
Geminid	December 07 - 17	December 14	120	Asteroid 3200 Phaethon
Ursid	December 17 - 26	December 22	10	Comet Tuttle

        

           Witnessing a shower of meteors is another level of joy in itself. The natural fireworks in the sky often light up the eyes, but there are times when one is putting a lot of efforts and still get to see a very few or almost no meteors. One of the most eye-catching and promising meteor showers is the Geminid meteor shower. More than a hundred meteors can be seen overnight from a dark place. Observers living in a light polluted city may have to go around 25-30 km away, outside the city. If the sky is clear, amateur observers can enjoy the bright meteors from Geminid, even from their backyard.

✍ Sonal Thorve