comet Ison

This time-lapse image shows comet Ison approaching and leaving during its slingshot around the sun (represented by the white circle) -- on Nov. 28, 2013. You can see the curve of the comet's orbit path.


What happens when the sun eats a comet? It gets terrible solar gas.

No one can blame us for thinking the question sounds like a joke. After all, the sun doesn't actually "eat" a comet, but it can pretty much consume it and, on occasion, "burp" it out. And as you'll see, our punch line is more serious than you'd think.

When you see a picture of a comet in the sky, you're generally seeing a glowing ball followed by an ethereal-looking trail of gas. The center of the comet (or the nucleus) is made up of rock, gravel and ice. And that nucleus can be less substantial than you'd think, if you're judging it based on the comet's gigantic coma (the glowing ball that surrounds the nucleus and consists of gas). For instance, when the comet Ison passed by the sun in 2013, its nucleus was only about 1.2 miles (2 kilometers) across [source: Plait]. Even with the relatively small nucleus (compared, say, to Hale-Bopp's 1997's appearance, with its roughly 20-mile, or 32-kilometer, nucleus), Ison still had a whopping 80,000-mile (120,000-kilometer) coma. And that's not even taking into account its 5 million-mile (8 million-kilometer) tail [source: Plait].

Just like planets, comets orbit the sun. And some of those comets come super close to it: They're called "sungrazers" because their path allows them to get all up in the sun's business. Since the sun is a star and not a rocky planet like Earth, it doesn't have a hard core for the comet to hit, as it's only composed of gas. What does that mean when a comet gets too near it?

There are a few possibilities. One is that the comet makes the flyby successfully; its nucleus withstands the heat and it survives the trip. (Keep in mind it disintegrates eventually on its orbit anyway, as the sun evaporates the ice of its nucleus.) Another possibility is that the comet approaches the sun but disintegrates before it can hit it. Lastly, it may emerge on the other side (and perhaps put on a fantastic light show as it does).

Let's get a little closer to the heat, and see what happens when a comet gets caught in the sun's web.