[meteorite-list] "Comet shower"

[Larry Lebofsky]

Hi Darren:

This one I think I can answer and not get into trouble with anyone in the 
astronomy field.

Meteor shower:

Usually related to a comet (or sometimes asteroid; extinct comet??) or 
sometimes not (comet long gone). Comets have tails. This material is small 
(look at Stardust) and spreads out along the orbit of the comet. Since this is 
long (all the way around the orbit) and fairly broad, we pass through it each 
year (sometimes we go through thicker regions and get meteor storms). This is 
a meteor shower and these are named after the region of the sky where we see 
the majority "come form." There is no documented fall from a meteor shower 
(stuff too small, so fragile?).

Comet shower:

Humans probably have never witnessed one. This is one of the theories for mass 
extinctions on Earth. A "thing" (passing star or planet X) plows through (or 
comes close) to the Oort cloud. Lots of objects are perturbed out of their 
orbits and some now have new orbits that bring them in close to the Sun (and 
the Earth). Since there are lots of them and have different orbits, they come 
through the inner Solar System over long periods of time. If the thing that 
does the perturbing is also in orbit around the Sun, the perturbing can happen 
periodically (periodicity of extinctions). 

While we see showers regularly and can associate them with certain comets and 
at soom level predict when there will be more or less (a little better than 
reading tea leaves), this is a real thing. Not so for comet showers. No 
evidence for "Planet X," far different than the on-going discussion. No 
evidence for extinctions being periodic or over a period of time (many people 
still claim there is a periodicity, but them more people will disclaim it). 
Still not solid proof and no bit object ever seen (though who know for sure).

I hope this answers your question, Darren. The only controversy is whether or 
not comet showers have ever happened and if so, what caused them. So far there 
is little evidence for there ever having been one (after the Late Heavy 
Bombardment 4 billion years ago).

LArry 

Quoting Darren Garrison <cynapse at charter.net>:

> Okay, this explanation of "meteor shower" vs. "comet shower" surpasses the
> new
> definition of planet to win Weird Science Defintion of the Week.
> 
> Is it just me, or would a better answer have been to explain how meteor
> showers
> ARE produced by the debris of comets (which is where the question seemed to
> be
> leading) and not to interpret the question as being "do lots of comets hit
> the
> Earth at once"?
> 
> http://www.earthsky.org/shows/listenerquestions.php?date=20040417
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