Comets

Comets are like dirty cosmic snowballs; they are made up of ice, frozen gases, rock and dust, and generally range from a few hundred metres in diameter to tens of kilometres wide.

They are most often found in the outer solar system, far away from the Sun, where they remain frozen and difficult to observe.

However, their elliptical orbits occasionally bring them close to the Sun, causing their ice and frozen gases to vaporize and form tails behind them. This effect makes comets much easier to spot from Earth.

Asteroids

A type of minor planet, contain a lot of the same elements as the solar system's rocky planets, including carbon and metals.

Their sizes can vary – many are less than 10 metres wide, but the largest asteroid ever detected, Vesta, is 530 kilometres wide.

Most are found in the asteroid belt between the orbits of Mars and Jupiter.

SOURCE: Canadian Space Agency