Expert: Tom Whiting - 6/23/2009

Question
Dear Tom.  I was outside this morning between 4:50 and 5:10 am CDT in San Antonio, TX.  I was looking (naked eye) in the vicinity of Orphiucus and there was a very large flash (25x larger than nearest brightest star).  The flash was just "on then off", but it flowed; it was graceful.  I checked with the airport and there was no known aircraft, satellite, etc.
What could it be?  I have been humbled by the night sky for 45 years now, and I have never seen anything like it.  Thank you for your patience.

Gratitude, Alex

Answer
Hi Alex,
Are you aware of Iridium Flare Satellites?  There are over 90
of them and they get as bright as -9th magnitude when they flare
up (that's as bright as a quarter moon in a pinpoint of a flash).
Of course, it's just sunlight glinting off of the mirrors onboard
the satellite. (on average though, the get as bright as Venus
at -4th magnitude, unless you are right on centerline).

And your time sounds about right because almost all Earth-orbiting
satellites are seen 2 hours after sunset, and 2 hours before
sunrise (as you already know).
The only way to check it out is go where we get our predictions
for those Iridium Flare Satellites, and that's on
http://www.heavens-above.com

You have to sign up (it's free) then pick a specific location very
close to your location because Iridium satellites are + or - 20 miles
on either side of centerline.  You can even, on that website,
backtrack 48 hours to see which Iridium satellite it was that
you saw.  You can also get all satellites for your area down
to 4.5 magnitude, plus any ISS passes for the night too.

We watch for them all the time, in fact, we in Erie get a -8th
magnitude one tomorrow night at 10:45:42 pm EDT at azimuth 56 degrees
and 39 degrees high.  You can set your watch by them, and you
have to be looking at exactly that spot in the sky.  In fairly
dark skies, you usually pick up the 5th magnitude satellite about
20 seconds before and after, they flare up.
Hope this helps,
Clear skies,
Tom Whiting
Erie, PA

FOLLOW UP:
Oh, and BTW, "oh fee EWE cuss"  is spelled Ophiuchus...the snake
holder. There's no 'r' in it... don't feel bad; early in my
astronomy career I used to call it  orp FEE chus...and misspelled it too, with an 'r'.  (The genitive case is easier...oh fee EWE ki,
and generally we just shorten that to  oh FEE ki....with long e's
and long i.)  And by ewe I mean the long sounding 'U'.

And BTW, it's the 13th Zodiac constellation, as the sun, moon,
and planets all travel thru the snake holder, but we don't really
believe in that astrology stuff anyway....but it IS on the ecliptic
too, between Scorpius and Sagittarius.  I guess the old time astrologers just didn't want to have a snake holder as part of
their....false repertoire.
Clear skies,
Tom
FOLLOW UP:
Oh, and you're wasting the airport's time calling them...those guys up in the tower aren't up on all the Iridium flares or the Space Station (ISS) or any of that stuff in Earth orbit.
You have to dig this stuff out yourself on that website I gave you.
Tom
ADDITIONAL FOLLOW UP:
All those Iridium satellites are in polar orbit..N to S or S to N,
not equatorial (W to E) orbits. So the bright object you saw was
either traveling N to S or S to N, irrespective in what part of
the sky (compass direction) you saw it.
tom