## Shop Windows to the Universe

Become a nitrogen atom in the nitrogen cycle in our Traveling Nitrogen Classroom Activity Kit/Game. See all our games, activity kits and classroom activities.

# Interactive Comet Animation

The interactive animation (below) shows some things about how comets work. Click the "play forward" button to make the comet move around in its orbit. You can make your own "custom comet" by adjusting the orbit size and the eccentricity (how "oval-shaped" the orbit is) of the comet's orbit. Click the "Closeup" tab to get a zoomed-in view of the comet. Click the "Pick Comet" tab if you want to look at some actual comets.

Can you make a comet with a really long tail? How long do comets take to orbit the Sun? If you want to find out more about comets, there is more information further down on this page.

You will need to have the latest version of the Flash player to see this animation.

Things you may have noticed:

• A comet's tail gets longer when it is close to the Sun. Heat from the Sun melts (actually sublimates) the ices that a comet is mostly made of. The comet's tail is made of material from the comet; gas from the ices and dust that is mixed in with the ice.
• A comet has two tails. The white one is made of dust. The blue one is ionized gas. Both point roughly away from the Sun. The solar wind and radiation pressure of light from the Sun "blow" them outward.
• There are two major factors that describe a comet's orbit: the size of the orbit (technically, its "semi-major axis") and the eccentricity. The size is like the radius of a circle. The eccentricity is tells how "oval-shaped" the orbit is. A small eccentricty means the orbit is roundish; a circle has an eccentricity of zero. A large eccentricity (close to one, such as 0.8 or 0.9) means the orbit is a very long oval. Halley's Comet has a high eccenticity.
• If a comet has an orbit with a high eccenticity, it moves much faster when it is near the Sun than when it is far from the Sun.
• If a comet has a large orbit, it takes a long time to go around the Sun. Some comets are "short-period" comets that take five or ten years to complete an orbit. Some comets are "long-period" comets that take decades, centuries, or millenia to orbit the Sun. Long-period comets originally came from the Kuiper Belt or the Oort Cloud.

#### Shop Windows to the Universe Science Store!

Our online store includes books on science education, ranging from evolution, classroom research, and the need for science and math literacy!

## Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

## Kepler's 2nd Law: The Speeds of Planets

Kepler realized that the line connecting the planet and the Sun sweeps out equal area in equal time. Look at the diagram to the left. What Kepler found is that it takes the same amount of time for the...more

## Orionid Meteor Shower

Meteor showers are times when you can see a lot of meteors in one night. There are several different meteor showers. Each meteor shower happens at the same time every year. There is a meteor shower in...more

## Leonid Meteor Shower

The Leonid meteor shower is one of several major meteor showers that occur on roughly the same date each year. The Leonids typically "peak" (are at their greatest level of activity) in mid to late November....more

## Meteor Showers

A meteor shower is an astronomical event during which many meteors can be seen in a short period of time. Most meteor showers have a peak activity period that lasts between several hours and a couple of...more

## Meteors

Meteors are streaks of light, usually lasting just a few seconds, which people occasionally see in the night sky. They are sometimes called "shooting stars" or "falling stars", though they are not stars...more

## Geminid Meteor Shower

Meteor showers are times when you can see a lot of meteors in one night. There are several different meteor showers. Each meteor shower happens at the same time every year. There is a meteor shower in...more