Expert: Tom Whiting - 7/26/2009

Question
Mr. Whiting,

 My friend and I have been star-gazing for some time now. We usually see little shooting stars that are quite a distance away and only last for about 1 second or less. But tonight (7/24/09) around 10:30, we saw an amazing shooting star that lasted for about 2-3 seconds. It was very bright and we could actually see the tail sort of glittering and when it disappeared, it seemed to turn to glowing dust. Then about 5 minutes later we saw an even brighter shooting star and this one flickered like a flare or a firework and lasted about the same amount of time. My question is...were those just random shooting stars, or were they part of a known meteor shower? Also, I live in Wichita Falls, TX which is in the north-central part of the state. Is there anything scheduled that I could look for, perhaps something as brilliant as I saw tonight? Thanks so much for your time!

-Evan

Answer
Hi Evan,
Actually, what you and your friends saw was a "typical" random night out under the starry night sky during the summer months.  We seem to get more sporadic meteors during our summer and autumn months (5-7 per hour) as opposed to the time frame of Late December until late spring (1-2 per hour).  Why one side of our orbit is "dirtier" than the winter-spring side, is unknown.

The meteors you are reporting as either small diameter...(or more distant)...may be neither.
(In the late spring many of us are fooled by an intermittent 'fire-fly' high up...as a meteor.)
With a single light at night, the eye only sees brightness (or dimness)...not size or distance. There is no way to tell size and distance of a singular light without triangulating with multiple, widely separated, simultaneous observers, or with a very large telescope and other exotic equipment.  Our eye can only accurately report brightness, not size or distance.  There is no depth perception available with one singular event.
Some size of the particle can be inferred by length of time and brightness. The typical meteor is a grain of sand size or smaller. Brighter ones infer a pea size or even marble size object impacting the atmosphere, but that's as far as we can go.  Most meteors self-destruct from 100 to 60 miles high.  {The stars, planets, and any unidentified 'mysterious' lights are the same way.  We see brightness only; size or distance is not available to a single group of observers.}

There are no MAJOR meteor showers in late July, like the Perseids of August 11, the Leonids
of November 17, or the Geminids of December 13...however the Perseids have just begun at one
or two per hour...they will all come from the constellation Perseus, underneath Cassiopeia,
the Big "W" rising in the northeast. All these major showers run for several weeks using the standard bell-shaped Gaussian distribution curve, peaking on the night of maximum at a rate of 60-100 per hour on that night, or 1 - 2 meteors per minute.
There are a few minor showers (1-5 per hour) running in late July; the Piscis Austrinids, the
Delta Aquarids on July 28 (5-10 per hour) and the Alpha Capricornids on August 30. So combined,
one can expect an average of 10-20 meteors (counting 5-7 sporadics) per hour under dark, moonless, clear skies in late July and early August, with the Perseids slowly increasing their
numbers up to August 11.

Oh, a word on terminology here...astronomers don't like to use the words 'falling or shooting stars', as this impacting  "space junk" has nothing to do with stars. We prefer, and use, the term meteor. In fact, it's a meteor while giving off light and heat, a meteoroid before atmospheric impact, and meteorite if the object happens to strike the surface of the Earth.
Hope this helps,
Clear Skies,
Tom Whiting
Erie PA      

FOLLOW UP:
Oh, so yes, what you saw were just random, sporadic meteors entering the atmosphere. We can
never predict when that will happen. Even with the annual meteor showers, we have no idea
when a super-bright one will occur at any point on the Earth's surface. And even with the
Annual showers, we can only partially guarantee you a certain NUMBER of meteors on a given night, not their brightness. (Basically, you and your friends out observing just...got lucky...that particular night with 2 very bright ones that close together). They probably weren't even
related, because an an average impact speed of say, 20 miles per second, those two particles
would have been (5 minutes = 300 seconds) and 300 x 20 miles per second equals a separation
distance of 6000 miles. So yes, those were probably just random, sporadic meteors that you saw.
Clear Skies,
Tom   

ADD ON:
Oh, the glowing after-trail is a result of the marble-sized meteor ionizing the surrounding
rarified air at altitude.  This glow can persist for a matter of seconds, or even for several minutes, depending on the size and entry speed of the incoming meteoroid.
The flickering is caused either by high altitude intermittent thin haze layer, or the particle
itself may have a high rotational speed, and if it's peanut-shaped and tumbling end over end,
it will appear (like a tumbling or rotating artificial satellite) to change from bright to
dim and back to bright again very quickly, depending on how much surface area is exposed to the friction of the thin atmosphere up there at 80 miles high.
Clear skies,
Tom

ADD ON:
But sometimes we do get an early fireball from the Perseid shower, see
http://www.spaceweather.com/
Maybe this is the same one you saw, as picture is from Arkansas.
Tom