Re: Fireball or re-entry?

Jake Rees (jrburca@worldnet.att.net)
Thu, 18 Nov 1999 23:44:53 -0800

>Jake Rees wrote:
>>  Would not the fact that it was seen over a large
>> geographical area eliminate the possibility of it having been a re-entry
of
>> space junk?  Wouldn't a space junk re-entry be limited to a smaller
>> geographical area since they begin at 50-100 miles altitude?


>Jay Respler wrote:
>Don't see how that would affect the area of visibility. Meteors would
>burn up at the same altitudes.


Jay, I don't see it either now that you caused me to look closer.

I wrote that, because a low orbiting object near decay has a small circle of
visibility, as is easily seen with STS Plus, which I use.  I jumped to the
conclusion that this small circle was too small to take in the wide area
where the object was seen.  Small?  Wide?  All relative terms.  I found a
TLE which displayed a 76 nm altitude on STS Plus with the expected small
circle of visibility.  Well, it looks small compared to the circle of
visibility displays of more typical, higher satellites.  But, upon a closer
look, I see that the small circle is still large enough to cover several
midwestern and mid-southern U.S. states.

Still, as I think Bjoern was hinting, I believe meteors hit the atmosphere
much, much faster than space junk.  And therefore, it seems reasonable to
think that they would encounter enough friction to start burning at a higher
altitude where the air is thinner.  And so would be visible over a wider
area compared to a space junk re-entry.  But I have no data on it.

I think it is the west-to-east motion of the Earth in its revolving around
the Sun that would be the main factor in a west-to-east meteor hitting at a
shallow angle resulting in a slow moving meteor.  I had earlier written that
the Earth's rotation on its axis west-to-east was the factor.  Probably it
is a factor but not the major one.  I guess this is all basic stuff to the
more knowledgeable.  But, it's relatively new to me, i.e., how a meteor can
be slow moving lasting 10-30 sec.  I've never seen one like that, but
apparently they do rarely happen, from what I've gathered.

-- Jake Rees




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