(TU) Comets, Asteroids, and Meteors Lesson

Comets, Asteroids, and Meteors

There are other celestial bodies besides stars and planets in space. These other bodies are comets and asteroids.

What is a comet?

Comets are chunks of ice and dust, carbon and silicon whose orbits are usually very long, narrow ellipses. You could think of a comet like a dirty snowball. The exaggerated ellipse that a comet normally travels is good news for Earth. This elliptical orbit results in very few comets traveling near Earth and when they do they can only be viewed for a very short period of time. Comets do orbit closely past the sun. As a comet orbits around the Sun the energy from the Sun heats the icy comet up turning the ice into gas and releasing dust. The gas and dust form an outer layer around the comet called the coma.

See description of diagram Links to an external site.

Comets Have Three Parts

Nucleus - the solid core of the comet

Coma - the outer layer of dust and gas around the comet

Tail - as a comet orbits past the Sun the solar winds from the Sun push the gas (bluish color) and dust (white) from the comet away forming the comet's tail. A comet's tail is its most distinctive feature. As it approaches the Sun it develops an enormous tail of luminous material that extends for millions of kilometers away from the Sun. When far from the Sun, a comet's nucleus is very cold and its material is frozen.

Most comments are found in two regions of the Solar System: the Kuiper belt and the Oort Cloud.

Asteroids and Meteoroids

An asteroid is a small rocky body that orbits the sun. Asteroids are made up of carbon, rocks, and metals. Most asteroids in our solar system have orbits that lie between Mars and Jupiter. This region of the solar system is called the asteroid belt. Unlike comets, asteroids do not have a coma or a tail.

Meteoroids are small bodies that travel through space. Meteoroids are smaller than asteroids; most are smaller than the size of a pebble. Meteoroids have many sources. Most meteoroids come from asteroids that are broken apart by impacts with other asteroids. Other meteoroids come from the moon, from comets, and from the planet Mars. 

A meteor is a meteoroid that has entered the Earth's atmosphere, usually making a fiery trail as it falls. It is sometimes called a shooting star or falling star.

A meteorite is a meteor that has fallen to Earth. At least 100 meteorites hit the Earth every year. Meteorites have survived a fiery fall through the Earth's atmosphere and have lost a lot of mass in that process. Most meteorites burn up in the Earth's atmosphere; all that is left is a bit of dust. Every day, about 3000 tons of meteoroid dust falls to Earth.

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