Meteors, Meteoroids, and Meteorites

Meteors are often called falling stars or shooting stars. But they are not stars at all. They are simply little bits of matter plunging into the Earth's atmosphere and burning up in a fiery display.

There are a lot of small chunks of rock floating through space. These are called meteoroids. If one of these meteoroids comes close enough to the earth, it will be captured by gravity and plunge through the atmosphere.

As it falls toward earth it moves so fast that the friction of the earth's atmosphere causes it to burn up, or vaporize. This creates the bright streak of light in the sky that we call a meteor.

That bit of material may be no bigger than a single pea and is likely much smaller. It just gets so hot it even heats the air and makes it glow too.

Meteors usually completely burn up in the air, usually at an altitude of 60 miles or so. But some are large enough to survive and strike the ground. This surviving chunk of rock is called a meteorite.

Billions of meteoroids hit the Earth's atmosphere every day, but only a tiny fraction of those are large enough to be seen, much less to actually land on the surface before completely burning up

There are three basic types of meteorites -- stony, iron, and stony-iron meteorites. Most meteorites are of the stony type. Stony meteorites are composed of low-density materials similar to Earth's surface rocks.

Irons are most commonly found because they more obviously differ from Earthly rocks. Irons are very dense, and magnetic, and appear to have been somewhat melted by their fiery fall. Irons are composed of 90% iron and 9% nickel.

Stony-iron meteorites represent a blend between the stony and iron types

At certain times during the year, the number of meteors observed increases greatly, in some cases, exceeding 60 meteors per hour. These are called meteor showers. The material that produces them appears to be debris left by comets as they pass through the solar system. The comets themselves may or may not still exist, but the material they leave behind still does, and it follows the path of the comet's orbit. Each year as the Earth crosses that comet's path, it collides with the cometary debris, and we see the meteor shower.

The best time to observe a meteor shower is usually after midnight, perhaps two or three o'clock in the morning.

Observing meteors is best done with the naked eye. A telescope or binoculars is useless because they can only point to a small portion of the sky and no one can predict exactly when or where the next meteor will appear. It is best to lie close to flat on your back (say, on a blanket, a lounge chair, or the hood of your car) and generally gaze at a wide area of the sky to spot the meteors.

Showers are generally named for the constellation which contains their radiant, the point in the sky where from where the meteors appear to be originating. Most meteors actually appear some distance away from the radiant, but if you extend their bright paths back, they will all cross at the radiant.

The Geminid shower is generally the most reliable shower, while the Quadrantids are usually fairly sparse. The Perseid shower is the most popular, as it occurs during warmer weather in the Northern Hemisphere. Even though the Leonids are normally not very spectacular, about every 33 years the Leonids are a meteor storm, when for a limited time the rate may exceed 2,000 meteors per minute.

Major Meteor Showers

Date

Name

Rate

Radiant

Associated Comet

Jan 4

Quadrantids

40/hr

Bootes

None

May 4

Eta Aquarids

20/hr

Aquarius

Halley

Jul 28

Delta Aquarids

20/hr

Aquarius

None

Aug 12

Perseids

50/hr

Perseus

Swift-Tuttle 1862 III

Oct 21

Orionids

25/hr

Orion/Gemini

Halley

Nov 16

Leonids

15/hr

Leo

Temple 1866 I

Dec 13

Geminids

50/hr

Gemini

Phaethon