Asteroids, Comets and Meteoroids

Question 1 What are asteroids? Where are they located?

Question 2 What is a comet?

Question 3 When does a comet become visible to us?

Question 4 What happens to the tail of comet when it moves far away from the Sun?

Question 5 What is a meteor?

Question 6 What is the difference between a star and a shooting star?

Question 7 What are meteorites?

Asteroids

A large number of small objects made of rocks revolve around the Sun in the wide space between the orbits of the planets Mars and Jupiter in the Solar System. These are called asteroids.

Asteroids are small celestial objects which revolve around the Sun between the orbits of Mars and Jupiter.

The biggest asteroids are hundreds of kilometres in diameter whereas the smallest asteroids are only hundreds of metres in diameter. There are millions of asteroids which orbit around the Sun between the orbits of Mars and Jupiter. Each asteroid has its own orbit around the Sun. Asteroids can be seen only through large telescopes.

Comets

Comets are very small celestial objects made of gas and dust which revolve around the Sun in highly elliptical orbits and become visible only when they come close to the Sun.

As a comet approaches the Sun, it develops a long, glowing tail and becomes visible to us .

A comet becomes visible on coming close to the Sun because the Sun’s rays make its gas glow which then spreads to form a tail millions of kilometres long. The head of a comet is small and appears as a bright ball of light but its tail is very, very long.

A comet is a collection of gas and dust which appears as a bright ball of light in the sky with a long glowing tail when it comes close to the Sun. The tail of a comet always points away from the Sun . The tail of a comet grows longer as it comes nearer the Sun but it disappears when the comet moves far away from the Sun.

Comets are distinguished from asteroids by the presence of a long glowing tail. Asteroids do not have any glowing tail.

Comets revolve around the Sun just like planets. Each comet follows its own orbit around the Sun. The orbits of comets are very, very large and highly elliptical, due to which they remain very far off from the Sun most of the time and can be seen very rarely.

The period of revolution of a comet around the Sun is very, very large.

 

For example: Halley’s comet has a period of revolution of about 76 years. That is, Halley’s comet is seen after every 76 years. Halley’s comet was last seen in 1986. Each time a comet passes near the Sun, it loses some of its gas and ultimately only the dust particles are left in space. When these dust particles enter into the Earth’s atmosphere, they burn up due to heat produced by air resistance and produce meteors (or shooting stars)

Meteors and Meteorites

Meteoroids are celestial objects which range in size from tiny sand grains to big boulders of several hundred tonnes and revolve around the Sun in their orbits.

Meteoroids are much smaller than asteroids and comets.

Meteoroids are present throughout the Solar System. Meteoroids are members of the Solar System because they revolve around the Sun. When a meteoroid breaks away from its orbit around the Sun and falls towards the Earth, it becomes a meteor.

It is the visible path of a burning meteoroid that enters the Earth’s atmosphere which is called a meteor.

Meteors are the celestial bodies from the sky which we see as a bright streak of light that flashes for a moment across the sky. The meteors are commonly called shooting stars. When a meteor enters into the atmosphere of Earth with high speed, a lot of heat is produced due to the resistance of air. This heat burns the meteor and the burning meteor is seen in the form of a streak of light shooting down the sky, and it falls on the Earth in the form of dust.

A meteor (or shooting star) lasts for a very short time because the tiny rocky pieces (of which it is made), burn and vaporise completely in a few seconds due to the excessive heat produced by atmospheric friction.

A meteor is called a shooting star because, viewed from the Earth, it looks like a streak of starlight shooting across the night sky.

The main difference between a star and a shooting star is that a star has its own light but a shooting star has no light of its own. The light of a shooting star is produced when its particles burn on entering the Earth’s atmosphere.

A meteor which does not burn up completely on entering the Earth’s atmosphere and lands on Earth, is known as a meteorite. Meteorites are sort of stones falling from the sky

The meteorites falling on the Earth from the sky range in size from small pebbles to big blocks many tonnes in weight. More than 3000 meteorites, weighing around a kilogram or more, fall on the Earth each year in different parts of the world. Meteorites are believed to be the pieces of asteroids or comets which somehow strayed away from their orbit around the Sun and fell to Earth.

By studying the composition of meteorites, the scientists can get valuable information about the nature of the material of which the various planets (including the Earth) are made.