IMCCE Meteor Showers - Definition

Presentation

Meteor

A meteor is an atmospheric luminous phenomenon. It can then be the rainbow, a luminescent cloud, or a "shooting star".

Meteoroid

A meteoroid is a small body of the solar system (basically a rock), considerably smaller than an asteroid, and considerably bigger than a molecule or an atom (typically from a few microns to a few meters in size). When a meteoroid enters the atmosphere of the Earth, it collides with the molecules of the air at an altitude of roughly 100 km from the ground. Meteoroid are reaching the atmosphere at a fantastic velocity: 11 to 71 km/s, that is 2 to 10 times as fast as the shuttle at its reentry (or 40 to 240 times as fast as a bullet). Because of that, each collision is energetic enough to remove a piece of the meteoroid, which disintegrates this way. A plasma (electrons and ions) is created, and a fraction of the energy is converted into light. This is how "shooting stars" (meteors) are created. Most of the time, the meteoroid disintegrates completely before it reaches 50km of altitude.

Meteorite

A meteorite is a meteoroid big and/or slow enough to survive the entry in the atmosphere. It falls on the ground and can be found by anybody. If the meteorite is large and fast enough at the time it reaches the ground, it creates a crater.

Why is the expression "meteor stream" a non-sense?

To make it simple, one can say that the meteoroid is a piece of rock or metal in space, the meteorite the same piece found on Earth (after having lost aa huge fraction of its mass). Now the meteor only a luminous phenomenon. As a consequence, one can talk about a "meteoroid stream" (in space) or a "meteor shower" (=lots of luminous phenomenon in the Earth atmosphere), but the expressions "meteor stream" and "meteoroid shower" do NOT make sense. Now if you ever used the expression "meteor stream", do not worry too much: even professionals (including myself) have once made the mistake... However, now you know ;-)

Accoustic waves are also created but to be detected the meteoroid has to be large enough to penetrate in the lower parts of the atmosphere (French pages here).

Observation

Observing the meteors is among the easiest astronomical observations that can be done, if you only want to enjoy the show. Indeed, naked eyes are enough. No need for a giant telescope to witness a meteor shower. Care must be taken to do a valuable scientific observation though.

IMCCE is developping a program of observations, triggered by the impressive Leonid meteor storms (1998-2002) and followed up by the installation of the Lille Observatory Radio Meteor Station (LORMS)

You will find on the IMO web site all you need to know about the observation of meteors.

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Welcome

Introduction

Observation

CABERNET

Ephemeris

News

Bibliography

Acknowledgments

Credits

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