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(meteorobs) Re: NWM green fireball notes
I am taking the liberty of reposting a general note I sent to Joy alone, as
it contains no private comments and would be informative to other beginning
folks.
For nearly stationary fireballs, the best I have done was during the 1969
Geminids, a strongly purple -6m Geminid that moved only one degree in two
seconds, very near the radiant. A very short path was done by a -8m
fireball on the evening of 1973 Aug 18/19 ; I saw it go only 5 degrees in 6
seconds low in my SE. A Florida group got a lot of reports on it, and the
impact point was found to be around 50 miles away from me toward the SE
(much further than I was expecting when I saw it.). The observers that saw
it overhead got -12m out of it.
Norman
>Joy,
>
>There's enough information now that I can be satisfied that you saw a meteor.
>
>>be coming directly toward me, then it appeared to reverse without stopping or
>>changing speeds and it then went into an arc rising, peaking, and falling,
>>going from right to left. It was the brightest when it was nearest to me, just
>
>First, think of what it's like seeing a train in motion. Only if you are
standing on the tracks right in front of it would it be coming directly
toward you. Then it doesn't appear to be moving at all ; you can watch it
without moving your eyes to follow it. From the side you have to move your
eyes to follow it , either left-to-right or the opposite.
>
>A meteor coming directly at you would appear "stationary" by the same
principle, and it would not have enough time to show any motion. You would
think a headlight in the sky turned on, staying on for 1 or more seconds,
then turning off.
>
>It sounds like the meteor you saw came in at a fairly shallow angle,
allowing it to last longer and travel further in the atmosphere. And you
had a broadside view of it and not overhead, since it appeared to rise at
first, then peak, then drop down again. Somewhere in the middle of the path
it would be truely the nearest to you. At the beginning it is further away
hence would appear to be moving slower. Relative to the horizon this is
indeed an arc. But since the path is projected against the inside surface
of a sphere (think of a planetarium dome) , the arc is an illusion. The
path is actually straight as an arrow.
>
>
>>Thank you for your reply. It was the incredibly bright green light that
>>awakened me. I never heard a sound.
>
>Must have been as bright as a quarter moon, possibly even brighter. That
will cast strong shadows.
>
>>although I have seen an occassional "shooting star" in my life
>>they were very rapid and white and nothing like this.
>
>Most meteors are indeed fast and visible only as streaks. A handful are
slow or very slow, and these are the most fun to watch, like one shot out of
a Roman candle. You can follow the body easily for several seconds, and
with a broadside view you see it cover the maximum length path in the sky.
>
>> I had heard of the
>>August meteor showers but it is too bright in Washington, D.C.
>
>The Perseid shower (max on the night of Aug 11/12) has swift meteors.
Their paths are long in the early evening but at their shortest before dawn.
>
>>recall what possibilities went through my head except for the possibility of a
>>plane crashing.
>
>Jet fuel ought to burn orange rather than green. Hydrocarbons mostly
behave similarly ; even a Saturn 5 launch starts off with highly refined
kerosene, bright orange. Think of how leisurely a plane crosses the sky,
unless it is very near you. Even slow meteors appear to go faster than
planes if the meteor isn't coming in your general direction..
>
>>If fireballs do not arc, could this have been
>>something else?
>
>Are there any Air Force or other military bases out the direction of your
window? There are some rocket launches of various types, but these should
be orange or red-orange. I have never heard of a green launch.
>
> Is this size or intense light and color normal?
>
>Yes.
>
>>Are these part
>>of a shower? Are they more likely at any particular time of year or night?
>
>The very brightest ones tend to be bits of asteroid, very solid stuff made
of iron, nickel, or other metals, and/or stone; and with a fair possibility
of producing meteorites. The showers originate from comets shedding dust
particles which are clearly much smaller. The brightest shower meteors may
be clumps of dust particles; almost no chance of any of this material
reaching the ground..
>
>>What are the odds that I will see another if I don't stay awake looking for
>>them?
>
>Early evenings are surprisingly productive for fireballs, and most of the
casual ones are reported then because the majority of people are awake then.
With asteroids and their fragments going the same direction as earth around
the sun, the faster fragments can catch up with us from behind in the
evening. In the morning hours we are on the advancing side of earth so we
run into a lot more meteors then, but most asteroid matter is moving away
from us. We can still run into a slower piece for a rear-end collision.
>
>Evenings in February to April seem to have a higher number of fireballs ;
there may be some coming from a common source during that time. Otherwise
they are pretty much random.
>
> I hope you will forgive such elementary questions on a site with so
>>many obvious experts.
>
>Lots of beginners as well ! The experienced people should always be glad
to help.
>
>> I have bought a book by H.A.Rey and hope to learn much
>>more about the the heavens. Thank you again for your patience and answers.
>
>The best way to learn, for certain. The book came out shortly before I got
interested in astronomy, and I'm glad my mother got it for me at age 9 in
1955. I showed my wife the contrast between the dismal Sky & Telescope
charts and Rey's charts. You learn so much more, and so much faster, with
Rey. Seeing the pictures in the sky is still beautiful to me after this
many years. I always liked anything that glows in the dark : stars,
fireworks, meteors, fireflies, chemical luminescence and phosphorescence,
etc. So that's the common thread for my interests.
>
>Good luck in learning the sky yourself, and watch for upcoming shower
announcements.
>
>Norman
>.
>
Norman W. McLeod III
Asst Visual Program Coordinator
American Meteor Society
Fort Myers, Florida
nmcleod@peganet.com