Asteroid and comet are celestial bodies that are formed around 4.5 billion years ago when the solar system was formed. Although both orbit the Sun, they are different from each other in terms of their shape, size, atmosphere and formation. Let us see how they differ from each other!
Asteroid:
Asteroids are small, rocky objects that are smaller than planets. They orbit or revolve around the sun and are made of metals and rocky material. They are left over from that time when the solar system was formed. They are formed much closer to the Sun and thus due to the high temperature of the Sun, ice or water is not found in asteroids. They are also called planetoids or minor planets as they are made of same material as planets.
An asteroid can be a big piece or a cluster of small pieces held together by the gravity of the whole asteroid. The size of an asteroid varies too much as it can be few meters to hundreds of kilometers wide.
There are plenty of asteroids in our solar system. Majority of them are found in the asteroid belt, a region between the orbits of Mars and Jupiter. However, some are found in the orbital path of planets and move along the planets around the Sun. Earth also have asteroids that move along the Earth around the Sun.
Comet:
A comet is relatively smaller in size than Asteroid. It is a celestial body mainly made of ice, gases and dust. At the center, it has an icy nucleus surrounded by an atmosphere of gas and dust. They are formed far away from the Sun so their ice didn’t melt. However, when a comet comes closer to the Sun, the ice melts and produces a gaseous tail which is called coma and can be seen from Earth and can be thousands of miles long.
Comets orbit in an eccentric, highly elliptical orbit and their orbital period can range from few years to a million years or more. They travel in a specific path due to the gravitational pull of planets and the Sun.
Based on the above information, some of the key differences between Asteroid and Comet are as follows:
| Asteroid | Comet |
| It is a celestial object which is a huge mass of rock that orbits the Sun. | It is a celestial object with an icy nucleus that orbits the Sun. |
| Asteroids are made of metals and rocky material. | Comets are made of ice, dust and gases. |
| They are formed close to the Sun so they didn’t have ice or water due to the heat of the Sun and thus their surface is solid and rocky. | They are formed far away from the Sun so their ice didn’t melt and they have an icy nucleus. |
| They do not form tails. | They form tails when their ice melts as they pass through the inner solar system. |
| They are found in the asteroid belt. | They orbit the sun in the Oort Cloud and the Kuiper Belt. |
| Asteroids have an elliptical orbit. | They have an eccentric or highly elliptical orbit. |
| Their orbital period ranges from 1 to 100 years. | Their orbital period ranges from a few years to million years or more. |
| They are warmer than comets as they are close to the Sun. | They are icy or cold as they are far away from the Sun. |
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