A Moment of Science

Why Are Some Shooting Stars Fast And Others Are Slower?

Shooting stars can appear to be moving very fast or seem to linger in the sky. Why is there such a difference in speed?

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Photo: Eric Magunson (Flickr)

Did you find the shooting star? This photographer was lucky enough to catch a slower meteor in the sky.

You’re out on a clear, starry night with your best friend, looking for shooting stars. Look, there’s one! your friend shouts. But by the time you look, it’s gone. There’s another! she cries. Too late; you missed it. Then one comes along that seems to just amble across the sky, nice and slow.

Why is it that some shooting stars are so fast and others are much slower? Well, there are a few reasons.

What Is A Shooting Star?

Shooting stars are actually small meteors. Meteors are essentially icy rocks that come from space and burn up from the friction of entering our atmosphere.

A very small rock will burn up quickly and be gone almost before you can see it. A larger rock will take a while, and leave a long, bright streak in the sky.

Orbits Take Control

But there’s another reason. Remember that the earth doesn’t sit still in space: it’s orbiting the sun at 18.5 miles per second. Meteors that are coming towards us go faster across the sky because of earth’s forward velocity.

It’s like two cars passing in opposite directions.

Faster Meteors

In general, the fastest meteors to enter our atmosphere move at about 26 miles-per-second. Add earth’s forward velocity to that and it goes up to almost forty-five miles a second. Zoom!

These kinds burn up and are gone in less than one second.

Slower Meteors

Meteors that come from the other direction, however, are essentially chasing the earth through space. Their speed is decreased by the same amount as our forward velocity.

That’s like two cars passing while travelling in the same direction. The speeds cancel out and the passing car seems to be going much slower.

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  • scotcoleny

    So if this is true about shooting stars traveling in the same direction as the Earth, which makes perfectly good sense, then they should all be going in the same direction, right?
    Over the summer I’ve seen three slow shooting stars two going in the same direction and coincidentally the same direction as the Earths rotation. The third tonight was going from south to north moving at satellite speed and was bright then started to fade like going behind a cloud then just disappeared.
    Any answers?   

  • http://profile.yahoo.com/ZUHK7FOSKNSIQBNZQAAVDYSDKQ Anja

    I just got home and saw a meteorite going by really fast.  I thought it was a mistake because it was going so fast and also because it was going south to north.  I’m pretty sure it was a meteorite (although one cannot always be sure) because it disappeared right away.  The odd thing was also, it was crossing the path of airplanes they take just before landing at our local airport.  At first I did not even recognize it as a falling star but it must have been one.  What else could it be?  

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