For an hour or so each evening for the past week, just before I go to bed, I have been reading a book titled The Backyard Astronomer’s Guide, by Terence Dickinson and Alan Dyer.
It is considered one of the best reference books there is on the subject of amateur astronomy. I have not been attempting to read the book cover to cover, but rather I have been reading chapters and sections here and there about the things I am most interested. One being meteors and meteorites.
My interest in meteors and meteorites started many years ago when I was about 10 years old. I found a rock out in the middle of a farm field. It was smooth and flat and rounded at the edges on the top and bottom and sort of bubbly in between. It did not resemble any other rock I had ever seen. I was convinced I had found a meteorite. I hauled that rock a good 10 miles home. Later that week I went to the library and tried to look it up under meteorites. Nothing. But I knew what I had found so I kept it for years in my bedroom, until a junior high school teacher informed me it was some sort of limestone glacial rock that had probably been deposited during the ice-age. I still have that rock somewhere.
The word meteor comes from the Greek word meteoron, which translated means phenomenon in the sky. It is used to describe the streak of light produced as matter falls into the Earth’s atmosphere creating a temporary incandescence resulting from atmospheric friction. A meteoroid is matter revolving around the sun or any object in interplanetary space that is too small to be called an asteroid or a comet. A meteorite is, in effect, a meteoroid that has managed to reach the surface of the Earth without being completely vaporized.
The majority of meteorites are believed to be fragments of asteroids. Meteorites are classified into three broad groupings: stony, stony iron, and iron.
The most common meteorites are chondrites, which are stony meteorites. Radiometric dating would seem to indicate that chondrites are somewhere in the neighbourhood of 4.55 billion years old, which is the approximate age of the solar system. Other meteorite types which have been geologically processed are achondrites, irons and pallasites.
It is thought most meteors are formed by the decay of a comet nucleus and consequently follow the path of the original orbit of the comet. When the Earth’s orbit intersects a meteor “stream” a meteor shower is said to result. A meteor shower typically lasts for several days. A particularly intense one is called a meteor storm. Even as a kid growing up on the prairies, I always did like watching a good storm.
This is the sort of information one can gather from reading a book like The Backyard Astronomer’s Guide. It is also the kind of information that starts to swirl through your mind when you are looking up at the nighttime sky on a hot August night during something like the Perseids meteor showers.
Sometimes at night, when I am walking from the vehicle to my front door and I happen to stop and look up at the moon and all the stars in the sky, I hope that maybe, just maybe, this will be the night I am lucky enough to catch a glimpse of one of those short-lived, random, momentary streaks of light that every so often arches their way across the night sky.
On other occasions, especially on a warm summer’s evening when I know beforehand there will be a waning moon to cast very little light and the sky will be clear of clouds, well, that’s when I load up my iPod with Van Morrison tunes, put a six-pack of ice-cold Cokes in the little glass bottles into a cooler and head out into the back yard. That’s when I just like to sit back in one of my wooden Adirondack chairs to wait things out – knowing that if I sit there long enough, I will inevitably get to see any number of those wondrous streaks of light go shooting across the night sky.