Asteroid, Meteoroid â€“ What Is It?

Subodh Varma
15 February 2013, 03:37 PM IST

On the very night – 15 February 2013 - that an asteroid is slated to make the closest pass to Earth ever observed, a meteor shower over the Urals in Russia hit the headlines in the day. And this led to confusion – what is the difference between an asteroid and a meteoroid, or for that matter, between meteor and meteorite? And don't forget the comet – how is it different from an asteroid? Some people even said that the asteroid had exploded!

Here's the lowdown on all these terms:

Asteroid: A relatively small, inactive, rocky body orbiting the Sun. The asteroid flying by Earth tonight between 6pm and 9 pm GMT is 150 feet long and is just a huge rock with probably a lot of metals in it. There is a whole Asteroid Belt out there circling the Sun, between the orbits of Mars and Jupiter. Besides, there are Near Earth Objects (NEOs) that are closer to Earth asteroids.

Meteoroid: Very small chunks of rock debris orbiting around the Sun are called meteoroids.

Meteor: When these meteoroids get trapped by Earth's gravity and enter the atmosphere, the friction burns them up. These incandescent falling pieces of rock can be seen from Earth – they are the "shooting stars".

Meteorite: Usually, the meteors will burn up totally. But sometimes small bits survive and hit the Earth's surface. These survivors are called meteorites.

In other words, even an asteroid will become a meteor and perhaps a meteorite if it enters the Earth's atmosphere and burns up.

So what are comets? They are made of rocks and ice and have very elliptical (elongated) orbits around the Sun. As they come near the Sun, they get heated up and the evaporating ice causes a long 'tail' to be seen blazing through the night sky. Debris coming out of the comet's passage may cause meteor showers, but not necessarily.

Now sit back and enjoy DA 14, the asteroid that will pass by Earth at about 1 am tonight. In case you can't see it, try the live streaming video available from NASA.