A view of a star in the sky with a mountain in the background

"Comets are often called "dirty snowballs" of Space, due to its icy and dusty composition. They are mainly composed of water, carbon dioxide, ammonia and other frozen volatile materials. The most striking feature of comets is their bright tail, that form as they approach the Sun. When a comet approaches the Sun, solar heat causes frozen materials to sublime, releasing dust and gases that form a tail that always points away from the Sun. This tail is what makes comets visible from Earth." (Realistic digital artwork) (extreme quality), (hdr+)