Question

What are comets? write their composition. why is halley's comet called a periodic comets?

Answer 1

comets are icy celestial bodies which revolve around the sun. they have a tail. they sometimes get engulfed by the sun

Halley's comet is called a periodic comet because it revolves after every 76 years

Answer 2

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No doubt asteroids are different from comets.

Comets usually have tails and are made up of ice and debris sublimating when the comet gets close to the sun. And we have study above that asteroids does not have tails even they come closer to the sun. Let us tell you that astronomers have spotted tails in some asteroids like asteroid P/2010 A2. This happens when asteroid hit with other asteroids and dust or gas is ejected from their surfaces which create an effect of a tail. Therefore, such types of asteroids are known as "active asteroids" and they are rarely found.