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.
Page created February 25, 2004 by Randy Russell.
Last modified February 26, 2004 by Randy Russell.
The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/
at the University Corporation for Atmospheric Research (UCAR).
©1995-1999, 2000 The Regents of the University of Michigan; ©2000-06
University Corporation for Atmospheric Research. All Rights Reserved. Site policies and disclaimer