By Anna Edmonds
July and August are good times to look for shooting stars. If you’re patient and watch carefully, you probably can see one any clear night. They are ideal for naked-eye observing. And July’s better than January when you don’t have to wear winter clothes waiting outside for one to appear.
Astronomers usually call shooting stars “meteors.” They are grains of dust burning from the friction with our air. Most of them start about 60 miles above us, and they burn up in a wink. Sometimes they’re “fireballs” brighter than the planet Venus. If they explode, they’re called “bolides.” The few that are so big that there’s still something left to reach the ground are “meteorites.”
Meteors and meteorites are bits of debris that the Earth bumps into. The debris could be from the Moon, or from Mars, or maybe it’s left over from when the Solar System was being formed. That makes it old—about 4.5 billion years. Much of it seems to be what blew off the tails of comets when they whizzed around the Sun. The Earth gets a lot of such stuff—over 100 tons rains down every day. By studying meteorites from outer space astronomers are learning about the inner spaces of Earth. They suggest that we got some of our water originally from comets. And men from Mars?
Summer is the time of two big meteor showers, the Delta Aquarids around July 29 and the Perseids around August 12. Aquarids can average about 20 meteors an hour; the Perseids are usually more numerous—80 or so an hour. You have a better chance of seeing them after midnight than before. It’s like walking with the rain or into it: The earth gets more in its face when it’s facing into the shower.
Some people keep a record of the meteors they see. They list the day and the hour, the brightness, the name of the shower, how clear the sky is, and comments on unusual features. If there’s a chance that it has become a meteorite, they try to give directions to where it might have landed so it can be found.
Look up on a clear night this summer. You might see an ancient Martian wink at you.