Comets Have Two Tails.

Comets have two tails.

There are two types of comet tails: dust and gas ion.

A dust tail contains small, solid particles that are about the same size found in cigarette smoke. This tail forms because sunlight pushes on these small particles, gently shoving them away from the comet’s nucleus. Because the pressure from sunlight is relatively weak, the dust particles end up forming a diffuse, curved tail.

A gas ion tail forms when ultraviolet sunlight rips one or more electrons from gas atoms in the coma, making them into ions (a process called ionization). The solar wind then carries these ions straight outward away from the Sun. The resulting tail is straighter and narrower. Both types of tails may extend millions of kilometers into space. As a comet heads away from the Sun, its tail dissipates, its coma disappears, and the matter contained in its nucleus freezes into a rock-like material.

Comets don’t like the sun.

Comets lose a lot of mass when they go by the Sun. A lot: some shed hundreds of tons of material per second. That’s actually a small fraction of the mass of a comet, but given time, and lots of solar passes, it adds up. Every comet we see is slowly dissolving in space. Eventually even the mighty Comet Halley will be gone, broken down into a swarm of rocks, gravel, and dust once its gas is gone.