Asteroids and comets that sometimes come close to Earth and make people nervous! Astronomers are always closely watching the movements of the two bodies to prevent them from colliding with the Earth. What is the difference between an asteroid and a comet?
● Asteroid
An asteroid is a celestial body orbiting the sun that is smaller than a planet. Asteroids were created when the solar system was forming 4.6 billion years ago. Due to their small size and lack of gravity, they do not coalesce into planets and mainly orbit between Mars and Jupiter. This is called the asteroid belt.
An asteroid that falls to Earth and is found on the surface is called a meteorite. Scientists use meteorites to determine the composition of asteroids. Asteroids are rocky masses of carbon, silicon, and metals. Unlike comets, they contain very little volatile matter and are therefore dense. They differ from comets in that they do not have a gaseous coma or tail.
An asteroid with a diameter of more than 140m and approaching within regarding 7.5 million km of the Earth is called a ‘potential threat asteroid’. If this asteroid collided with Earth, it might destroy an entire area. Because of this, scientists are devising strategies to prevent collisions, such as applying physical shocks to asteroids to change their orbits.
● Comet
A comet is a celestial body made of ice and dust. Like asteroids, they were formed when the solar system was forming. Comets are similar in size to asteroids, but they are less dense because the empty space between the ice is filled with gas. The comet’s nucleus is small, several kilometers long, and looks like a faint spot when it’s far from the sun, but it forms a long tail as it gets closer to the sun.
Why do comet tails appear? The nucleus of a comet is a solid mass containing volatile matter. When a comet approaches the sun, the surface of the nucleus evaporates, enveloping the nucleus in a giant gas called ‘coma’. Dust in the coma is then pushed back by the solar wind, which forms the comet’s tail.
The comet’s home is known as the ‘Oort Cloud’, which encircles the outermost part of the solar system. The Oort Cloud is made up of ice fragments and dust, and when it escapes the cloud under the influence of a celestial body passing next to the cloud, it becomes a comet as it approaches the sun.
