What is a Meteor Shower?

If you have never seen a meteor or, as some people call them, a "shooting star" or a "falling star," then I recommend going outside during late July or the first half of August, grab a reclining lawn chair, lay back, and look straight up. It is best if you do this close to midnight or later and, if there is very little light pollution and no moon in the sky, you are likely to see a meteor within a matter of minutes.

A meteor will appear as a fast-moving streak of light that will only last about a second or two. It may seem unexciting, but that meteor is traveling thousands of miles per hour and, in most cases, is smaller than a pea!

So, how does a pea-sized (or smaller) object from outer space manage to put on such a show? The truth is you are not seeing the actual particle from space, but the reaction of the gases in our atmosphere as they react to friction caused by this rapidly moving object as it falls through the sky above you. Most meteors completely burn up in the atmosphere at altitudes of between 60 and 80 miles.

The particles causing the appearance of a meteor are an interesting class of astronomical objects. The name given to them actually changes depending on where they are. While moving through space, the particles are referred to as meteoroids. When they enter Earth's atmosphere they are referred to as meteors. If they happen to be large enough to hit the surface of Earth they are referred to as meteorites.

Although there are meteoroids that are orbiting the sun alone, there are other meteoroids that are traveling in a cloud of meteoroids. This later group is moving within the orbit of a comet or an extinct comet. Astronomers discovered back in the 19th century that comets shed particles every time they passed close to the sun. There are some comets whose orbits are located very close to the orbit of Earth and, at certain times each year, Earth passes through a cloud of particles, which results in a meteor shower.

Meteor showers are given names that are derived from the constellations they appear to radiant from. One of the most famous meteor showers is the Perseid shower of August. Peaking on the night of August 12/13, the Perseids usually produce rates of between 40 to 60 per hour for most observers. Observers with better eyes and ideal observing conditions (i.e., no light pollution and very clear skies) have reported seeing between 80 and 100 per hour. Other strong meteor showers that are visible every year are the Quadrantids, Eta Aquarids, Orionids, and Geminids.

Meteors can be observed during any time of the night; however, more meteors will be visible after midnight than before midnight. The reason for this is simple and has to do with the rotation of Earth. Following sunset, you are basically on the trailing edge of our planet as we move around the sun. Any meteors that you see have had to catch up to Earth, but many meteors move slower than our planet and will not catch up at all. After midnight, Earth's rotation has now placed you on the leading edge of our planet as we move around the sun. We are now sweeping up slow particles, while the faster particles are entering our atmosphere at much higher speeds than before midnight. Higher speeds means the meteors will also be brighter. So, in general, we tend to see more meteors and brighter meteors during the pre-dawn hours.