Shooting Stars

The scientific name for a shooting star or falling star is a meteor. They start out as small rocks in space, anything from the size of a grain of sand to a boulder, which means that they’re invisible from the Earth. But they’re travelling very fast indeed – anything up to 71 kilometres a second (44 miles per second), and as soon as one enters the atmosphere, friction heats it up until it glows, and that’s a shooting star. Usually, they start to glow when they’re very roughly 100 km (60 miles) above the Earth, and disintegrate above 50 km (30 miles). A few of the bigger ones last long enough to hit the Earth. Once that’s happened, they’re called meteorites.

(Isaac Asimov wrote an article, “Why do the Gods Hate Kansas?” because Kansas has far more than its fair share of meteorites. Actually, Kansas gets hit by the same number of meteorites as everywhere else. It’s just that there are very few stones in Kansas, so the meteorites are easy to find.)

You might see a shooting star any night of the year, but you’re far more likely to be lucky some nights than others. This is because comets leave dust trails behind themselves. When the Earth hits a dusty part of its orbit, the meteors rain down in a meteor shower, sometimes more than one a minute.

Since the Earth takes exactly a year to go around its orbit (by definition), we reach the dusty patches on the same date each year. This produces a line-of-sight effect where the meteors appear to radiate out from one particular constellation in the sky, a different one for each annual meteor shower. So each shower is named after that constellation.
The best one is usually the Persaids, in August.

The best time to observe meteors is whenever there’s no moon. Most showers get better after midnight, so you’ll often need warm clothing. Chose a place with a clear view of the sky and (preferably) no street lights. (On La Palma, any of the astronomical viewpoints would be ideal.) If possible, lie back on a blanket or recliner. Give your eyes time to adjust (ideally, 15 minutes.) It’s best to look away from the radiant, so you can see where the meteor came from. If you want to make notes of how many you see, it’s easier to use a tape recorder than a pen and paper.