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Explore Asteroids, Comets and Meteors

Flying Space Rocks

Rock and ice are the main ingredients of asteroids, comets and meteors. These flying rocks orbit the sun and sometimes come close enough to Earth to see.

Asteroids

Asteroid Gaspra The Asteroid Gaspra.

Asteroids are made of rocky and/or iron-nickel material and most are found in an orbit between Mars and Jupiter. Most are pitted with impact craters and dust left from collisions with other objects in the solar system.

Asteroid Ida and Dactyl Some asteroids have other asteroids orbiting them as in the picture at right: the Asteroid Ida and its moon Dactyl.

A group of asteroids orbit the sun called Near-Earth Asteroids because they are somewhat close to the Earth and occasionally may cross Earth's orbit. Could any hit the Earth? Click here for more about
Near-Earth Objects.

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Astronomy Information for Elementary Students.

Comets

Comet Hale-Bopp The comet Hale-Bopp pictured at left is an example of the large tails comets can have.

Comets are believed to be in long eliptical orbits that take them from beyond the orbit of Uranus to around the sun. These objects are found in the Kuiper Belt between Uranus and Neptune and the Oort Cloud from way out beyond Pluto.

The name "comet" comes from the Greek meaning "long-haired" because of their tails. Chinese astronomers record several observations as well. Comets throughout history have been thought to bring bad luck but these are just natural phenomena of the solar system.

The nucleus of a comet is like a ball of rock and dirty snow. As these objects get close to the sun the frozen gases and dust begin to heat and cause a long tail of vaporized gases, dust and debris to flow behind them. As it melts, a cloud of gases and dust forms a coma. The head of the comet is the nucleus and coma together.

Because of their orbits we can see them come back from time to time. Halley's Comet appears about every 76 years, for example.

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Astronomy Information for Elementary Students.
Stardust mission and Captain Comet
Pluto/Kuiper Belt mission

Meteors

Meteors, known also as shooting stars, are usually sized from a grain of sand to about a softball. As the meteor enters the Earth's atmosphere it becomes very hot due to friction like when you rub your hands together for a few moments. They become bright and seem to streak across the sky.

When the Earth enters a meteoroid stream left by a comet, it produces a meteor shower. These showers can be predicted and come every year or so. They are named after the constellation that the meteors appear to be coming from. See the table below.

Common Meteor Showers
Name Date Seen
Lyrids April and June
Perseids August
Orionids October
Taurids November
Leonids November

These meteor showers can have over 100 meteors an hour and be quite spectacular. The best way to view these events are reclining or laying on the ground so you can see the whole sky without neck strain.

Meteors that survive the intense heat of friction with our atmosphere and hit the ground are called meteorites. Scientists have collected over 10,000 meteorites for study. These are made up of parts called Breccia, Carbonaceous Chondrites, Chondrites and Chondrules.

Terms

Here are some basic terms used for describing asteroids, comets and meteors. Find more astronomical terms in the Glossary.

Asteroid
Naturally formed solid bodies that orbit the sun, have no atmosphere and no signs of gas or dust coming from them. Most are found in orbit between the orbits of Mars and Jupiter.
Breccia
Rock made from pieces of rocks formed earlier.
Carbonaceous Chondrite
Stony meteorite containing chondrules and volatiles.
Chondrite
A stony meteorite containing chondrules.
Chondrule
Round, glassy part of meteorite made from silicates.
Coma
Roughly spherical area of vaporizing gases and dust around the nucleus of a comet.
Comet
Small bodies of rock, iron and frozen water and gases that orbit the sun in elliptical orbits. As they get close to the sun the gas vaporizes leaving a tail of dust and debris.
Comet Head
The nucleus and coma of a comet.
Dust Tail
Trail of gases, dust and debris left behind as a comet gets close to the sun.
Ejecta
Pulverized rock scattered by impacts on an object's surface.
Kuiper Belt
Small asteroids obiting the sun between the orbits of Uranus and Neptune thought to be the source of comets.
Light-year
The distance light travels in a year. About 1013 km or 6 trillion (thousand billion) miles.
Meteor
Rock, iron and/or icy body entering the Earth's atmosphere.
Meteorite
Any meteor striking the ground.
Meteoroid
A piece of comet debris. When the Earth enters a meteoroid stream left by a comet it produces a meteor shower.
Oort Cloud
A spherical region outside the orbit of Pluto thought to be the source for long-period comets with orbits of longer than 200 years.
Orbit
The path an object takes as it moves around another object.
Rotation
An object spinning about its center.
Volatiles
Carbon compounds, frozen gase and other materials that when heated vaporize.

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