What are asteroids and planetoids?« Back to Questions List

An asteroid is a relatively small, inactive and rocky body orbiting the sun. Sometimes, asteroids are called minor planets.  Larger asteroids are called planetoids.  While watching from Earth we see the sky. But beyond the sky, there are stranger things that will amaze us by their unusual shapes, spectacular appearances and magnitude.  The sun, planets and their moons alone are not the members of  the solar system. Asteroids, planetoids, comets, meteors etc are  also present in solar system.

Asteroids and planetoids are rocky remnants from the early formation of the solar system. Hence, they are aged more than 4.6 billion years. The belt between Mars and Jupiter houses many asteroids. Between these two planets, there is a wide asteroid belt and many of the ancient space left overs can be seen there orbiting the sun. Asteroids and planetoids vary in size. They can be seen in other places too. Some are seen in the orbital paths of planets.  This indicates that asteroids and planets  follow the same path around the sun.

Vesta, with a diameter of 530 km is one of the largest asteroids.   At the same time, there are asteroids with just 1o metres in diameter too. Total mass of all asteroids is estimated to be less than that of the moon of Earth. It is identified that more than 150 asteroids have companion moons, some of them have two moons.  They were formed at different locations at different distances from the sun. There re no similar asteroids.  Planets are round in shape, but asteroids are irregular. Majority of them are formed from different kinds of rocks. But in some of them,  clay and metals like nickel and iron are seen.

Many fictions depict the end Earth from a collision between our planet and asteroids.  Scientists have not ruled out the possibility. However, asteroids are far away from Earth. Because of the distance factor, many asteroids are invisible to eyes.  But, there are visible ones too.  Vesta with a large reflective surface is normally visible to the naked eye. It can be seen very rarely in dark sky when it is favourably positioned.  Small asteroids, passing by Earth also become visible for naked eye for short time.

A world organisation called Minor Planet Centre (MPC) has identified nearly 7,45,000 objects in the inner and outer solar system. Of these,  MPC has gathered enough information about 5,04,000   objects. None of these asteroids are close to Earth. Even a collision by a small asteroid can destroy a big city. A middle sized one can wipe out the humanity itself.

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