[Az-Geocaching] PAGING DR. SCOTTI.......

[Jim Scotti]

Hi Trisha,
     Was it moving relatively fast or relatively slowly?  If it lasted a few 
seconds, it was probably a meteor and was likely 50 to 100 kilometers above 
the ground while you watched it enter.  The brightness and glare tend to make 
such objects look much larger and much closer than they really are.  How 
bright was it - say compared to the full moon or Venus?  It's great when you 
see color in meteors.  If it was really bright, it might have resulted in a 
meteorite landing on the ground, but most likely, it burned up high above the 
ground.  If the object moved fairly slowly across the sky, then it is likely 
a re-entering satellite which might take a minute to slowly travel the entire 
width of the sky as it descends and burns up.  You can usually see satellites 
break up into lots of pieces as they slowly go across the sky - very much 
like the Columbia did as it broke up.  A meteor is moving much faster and 
doesn't last nearly as long, so it's relatively easy to tell them apart.
     I've had the pleasure of seeing several really bright fireballs in the 
sky and it's always really fun to watch them and think of what is causing 
them.  Most meteors you see in the sky are just little dust particles are 
maybe small pebble sized things.  The brightest things most people see in 
their lifetimes might be small boulders, maybe basketball sized or at most 
Volkswagen sized.  If you're really lucky, you might see a house sized object 
enter and if you are really _unlucky_, you might be under a skyscraper or 
football field sized object that explodes straight over your head (luckily, 
those don't happen too often!) like the Tunguska fireball over Siberia in 
1908.
     We're coming up on the best meteor season starting at about the begining 
of July and lasting through mid August, so get your lawn chairs out and turn 
the lights out and enjoy!

Jim.

On Thu, 16 Jun 2005, Trisha Brasher wrote:

>  (Sorry folks for the off-topic post, but hey, I gotta ask the
>  expert....)
>
>  Hey Jim,
>
>  We just saw something in the sky drop towards the ground, low. We
>  were facing (driving) north of Prescott Valley, approx 2058hrs, and
>  this green-light object looked BIG. It could have been a
>  meteorite...hopefully not a man-made object dropping out of the
>  sky.....if it was in northern AZ, it was big 'nuff. We have quite a
>  bit of visibility that direction, so if it was farther away, it was
>  HUGE.
>
>  Anything we need to know???
>
>  Trisha ~ Lightning
>

Jim Scotti
Lunar & Planetary Laboratory
University of Arizona
Tucson, AZ 85721 USA                 http://www.lpl.arizona.edu/~jscotti/