 Haley's Comet, Comet Halebop, and Comet Ison. What's the deal with all these comets and why all the excitement? Well, for starters, comets were formed in the very early solar system about four and a half billion years ago. They're just like time capsules that can tell us what the solar system was like when Earth was just a baby planet. Earth, right here, orbits the sun once every year. Comets, on the other hand, come from the very farthest parts of our solar system. Past the orbits of Jupiter, Saturn, Uranus, Neptune, from a place called the Kuiper Belt. Right here. Sometimes comets come from even farther out in our solar system from a place called the Oort Cloud. Our journey through the solar system takes us almost 800 million kilometers out to the Oort Cloud, which on this scale takes us two and a half kilometers down the road. Every once in a while, one of these comets goes astray and makes it into the inner solar system in a very elliptical orbit, just like this. We can create a fairly simple model of a comet using materials we find right here on Earth. Comets contain mostly ice, so I'll add some water. Minerals and dust containing some heavier metals are also found in comets, so I'll add some soil to represent those. Organic materials of carbon, hydrogen and oxygen are going to be represented by corn syrup. This window cleaner here contains ammonia, which comets have too. And finally, the carbon dioxide here in its solid form that we call dry ice. So this is what we get, a dirty snowball. This is called the nucleus of the comet. You can see it's uneven with pockets of gas inside covered in dirt. When this comet gets close to the sun, the heat and solar winds actually start to break the comet apart. The ice sublimates into gas as it heats up, and a tail forms behind the comet, always pointing away from the sun. A second tail is also formed from the dust particles being left behind as debris along the curved orbit of the comet. If a comet can withstand the gravitational force and the solar winds trying to pull it apart as it goes around the sun, it'll often return to us to put on a show in 200 years or less. For example, the well-known Haley's Comet last visited us in 1986 and returns every 76 years. Where will you be in 2061 when it returns?