- Grades: 1–2, 3–5
During late March and early April, 1997, Comet Hale-Bopp made its brightest appearance in the skies over North America. You'll have to wait 3,000 years to see it again!
How does a comet get a name like Hale-Bopp, where do comets come from, and what is a comet anyway? Here's the who, what, where, and how that you need to know.
How can you find out more?
Contact your local amateur astronomy club, college astronomy department, or planetarium to learn more about comets. Also, check out these Web sites:
Information on Comet Hale-Bopp for the Non-Astronomer
This site, sponsored by the Jet Propulsion Lab at NASA, delivers what its name promises. Visit this site and you'll come away with a good background on not just Comet Hale-Bopp, but comets in general.
Sky and Telescope's Comet Page
Sky and Telescope Magazine maintains this site which includes reprints of Comet Hale-Bopp articles and other general comet information. All of the information is clearly written for the everyday sky observer and is very well organized.
aphelion: The point in an orbit furthest from the Sun.
astronomical unit (A.U.): The average distance between the Sun and the Earth, often used when describing distances within the solar system. 1 A.U. = 150 million kilometers, or 93 million miles.
coma: The bright "head" of the comet, made up of dust and gas from the icy nucleus of the comet.
fluorescence: The light a gas gives off due to stimulation by light from another source. In comets, the molecules in the coma and gas tail give off light in response to sunlight.
long-period comet: A comet that originates from the outer part of the solar system, such as Comet Hale-Bopp, and follows an orbit around the Sun that takes many thousands of miles to complete.
nucleus: The solid, dusty iceball that is the core of the comet. The ice includes not just water ice but also frozen carbon dioxide ("dry ice").
orbit: The path that an object, such as a planet or a comet, follows around another object, like the Sun, due to their mutual gravitational pull.
perihelion: The point in an orbit closest to the Sun.
periodic or short-period comet: A comet captured into an orbit that stays within the orbit of the planet Pluto, such as Halley's Comet. The orbit may take a few years or a few hundred years to complete one cycle.
radiation pressure: The "push" that light gives off when it falls on something. Light coming from the Sun can push small dust particles away from the Sun.
solar wind: Ions of gas which stream rapidly away from the Sun. The solar wind follows the magnetic field of the Sun out through the solar system in a slightly spiral path.
sublimation: When ice turns directly into gas, without becoming a liquid.
tail: The portion of the comet which is blown away from the coma. There may be two tails, one made up of dust and the other of ionized gas.
(C)Paolo Candy. Viterbo, Italy, March 13, 1997, 3:40 UT
In this image, the ion and dust tails have been tinted different colors so that they are easier to see. The ion tail is blue and the dust tail is pink. To create this image, the telescope followed the path of the comet's nucleus during the 27 minutes of exposure time.