Shooting Stars

It was a clear night the other evening and I was looking up at the stars that fill the sky, as I do, and with a strike of luck I saw the most amazing shooting star streak across the sky. It seemed closer than the ones I usually see it had a flash of light sparkle from the front and trailed off with a glowing luminous tail before disappearing from sight. I’m sure so many of you have seen a shooting star flash across the dark of night, but, it’s not a shooting star your seeing, is it? Given our perspective of the stars and the streaks of light we see, they appear as though they have the same origin, or that they are the same thing. However, these shooting “stars” are much, much closer to us than a distant star. So, close in fact, that this light is a result of a piece of space debris entering our atmosphere.

You have probably heard of meteoroids, meteorites, meteors, comets, and asteroids. The key difference between comets and the rest of these objects is that they are in a consistent predictable orbit around the sun—for example; Halley’s Comet is visible every 76 years. The last time Halley’s Comet visited was in 1986. A comet is an icy celestial body and when its orbit brings it in closer to the Sun, the Sun warms it and as the ice melts just ever so slightly it releases trapped gases that produces something like an atmosphere that we call a Coma. This visible atmosphere escapes behind the comet creating a tail and a beautiful sight to be seen by all.

An asteroid is large and we would certainly know if one was heading towards us, as the asteroid is  famed for killing off our dinosaur predecessors. These giant celestial rocks originate from the Asteroid Belt (positioned between Mars and Jupiter), and rogue asteroids that are knocked out of orbit by other asteroids are usually the theorized culprit behind some of the hard to explain characteristics of planets positions and orbits. It is even thought that an asteroid carrying the organic materials for life crashed into Earth in its early days, and evolution took over from there. Some of the moons of other planets for example Phobos and Deimos of Mars are thought to be trapped asteroids. Asteroids that were dragged into Mars’ orbit by its gravity. We can see trapped asteroids on several planets throughout our solar system.

Neither comets or asteroids are the common shooting “stars” that most of us are wishing upon almost every night. We should change the song to, “…when you wish upon a meteor.” Okay, so what is the difference between a meteor, meteorite, and meteoroid and why these three names to describe essentially the same thing. A meteoroid is a small chuck of rocky-space-debris  broken off from either a comet or an asteroid, or even a chunk of Mars–assuming an asteroid struck Mars sending pieces of it into space and eventually crash landing on Earth–and as it enters our atmosphere the friction from atmospheric drag causes it to burn up. This flash of light from it burning up is called a meteor. If the meteoroid can survive the meteor stage and make it to the ground as just a small brunt up piece of celestial rock it is considered a meteorite.

A meteor sighting would appear to be random, and these meteoroids that hit the atmosphere all of the time range in size from small dust specks to larger boulder sized rocks. If they seem random than why do we have meteor showers that we can predict? As we mentioned already meteoroids break off from comets, and comets are in predicable orbits around the Sun. When those icy comets warm up in its closest approach to the Sun, that is when pieces of ice and dust break off and we can experience many meteors at once which we call a meteor shower. Maybe this is not as exciting as seeing an actual shooting star, but a star crashing into Earth would be in fact very scary.