Question

How long did it take comets to form?

Answer 1

Hint : Comets are cosmic snowballs of frozen gases, rock and mud that orbit the Sun. When frozen, they're the dimensions of a little town. When a comet's orbit brings it on the brink of the Sun, it heats up and spews dust and gases into an enormous glowing head larger than most planets.

Complete Step By Step Answer:
Comets are believed to possess two sources. Long-period comets (those which take quite 200 years to finish an orbit around the Sun) originate from the Oort Cloud. Short-period comets (those which take but 200 years to finish an orbit around the Sun) originate from the Kuiper Belt.
Astronomers believe comets materialized quite 4.5 billion years ago from the dust and gas of the pro planetary disk, a donut-shaped cloud of debris surrounding our newborn star. On the fringes of the disk, far away from the sun’s heat, fine grains of dust coated with frozen gases and water ice began clumping together.
Over time, clumps of dust assembled into ice-rich rocks, which later evolved into the mile-sized bodies that we observe today traveling among and much beyond the planets. Watch the video to ascertain an artist’s interpretation of the birth of a comet.

Note :
The biggest difference between asteroids and comets is their composition, as in, what they're made from. Asteroids are made from metals and rocky material, while comets are made from ice, dust and rocky material. Asteroids formed much closer to the Sun, where it had been too warm for ices to stay solid.