One of my favourite memories I have is seeing the comet Hale-Bopp that spent over a year in the sky, peaking in the spring of 1997. It was the comet of the century. I remember going out to look at it whenever I could, with its distinct double tail, and who can forget all the craziness of the Heavenâs Gate cult and their creepy matching shoes. It was quite a time. We just recently had another comet pass by, Comet Lovejoy. It was much fainter than Hale-Bopp; I tried a few time to find it, but with the light of the city around me, I couldnât find it.  Or, NASA has sent a probe to a comet, check that amazing mission out here: http://rosetta.jpl.nasa.gov/
Not mine sadly. Comet HaleâBopp, shortly after passing perihelion in April 1997.E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria
More and more, you hear space folk talking about the threat to earth by asteroids. More effort is being put into identifying them and the potential danger they pose to us. A large enough asteroid colliding with earth could cause a major extinction event, like the one that is often credited as being the cause of the dinosaurâs extinction. An impact whoâs dust and debris would block out the sun for years and kill almost everything on the planet. Fun, eh? It seems now that the more we look, the more weâre finding asteroids that âbuzzâ earth, as in, come between us and the moonâŠ..*gulp*
Another thing you may have heard in the news lately, was the Lyrids Meteor Shower, where one can expect to see several meteors per hour streak across the night sky as the earth passes through a stream of meteoroids likely left behind by a comet.Â
The peak of the 1997 Leonid meteor shower as seen from ABOVE, in Earth orbit, by the MSX satellite. Image courtesy of Peter Jenniskens.
Comets, Asteroids, Meteoroids? Wondering what the difference is? All of them are bits of space rocks and debris orbiting the sun, perhaps left over from the formation of our solar system, maybe a chunk of a planet that failed to form or was destroyed.
Comets are lumps of rock and ice, formed far from the sun. As they orbit and approach the sun, the ice(again, ice isnât necessarily just water) in them melts and creates whatâs called a coma, like a small atmosphere, around its nucleus. This is what gets swept behind and trails the comet, getting lit up by the sun and giving the comet a visible tail.Â
An Asteroid is entirely rock or metal, it doesnât have any ice, so nothing melts off of it to create a coma and tail as it gets closer to the sun.
A meteoroid is a tiny piece of comet or asteroid, or a just something significantly smaller, simple as that. But its not all simple. Iâve used two terms above, meteor, and meteoroid. There are also meteorites. Try not to mix them up, thereâs a difference between all three!
A Meteoroid is the actual chunk of rock or ice drifting through outer space. Should that meteoroid hit the earth and burn up in its atmosphere it will likely create aâŠ
âŠMeteor; the streak of light you see flash across the sky, caused by the meteoroid burning up. But, if the meteoroid doesnât burn up completely and makes it to the ground and someone finds it, that lump of rock or metal is called aâŠ
âŠMeteorite! Something we can examine and study, that may give us clues that help us understand how our solar system came to be. Some of these meteorites have even been found to have come from an impact on Mars or the Moon flung all the way here for us to find. I have no idea how they know this, so I wonât get into that here.
There you have it, space rocks: know the difference!
