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(meteorobs) Fwd: Leonids Meteor Colors


Again Ilan is not a subscriber: Please CC 'ilan@trendline.co.il' if you reply!

Note this is somewhat interesting in light of Asaf's observations that night.
Anyone care to comment on Florian Zschage's proposal of a "reddened earth
grazer" effect as an explanation? Would fainter (smaller) meteoroids be more
subject to such an effect, as they are more likely to be slowed by a shallow
angle of entry into the upper atmosphere? Just a curious line of questioning!

Lew Gramer <owner-meteorobs@jovian.com>


------- Forwarded Message

Date: Thu, 25 Nov 1999 11:23:12 +0200
To: Meteor Observing Mailing List <meteorobs@jovian.com>,
        Dr Peter Brown <peter@danlon.physics.uwodot ca>
From: Ilan Manulis <ilan@trendline.co.il>
Subject: Leonids Meteor Colors

Dear meteorobs members,

The following is a copy of a message dispatched yesterday to the IMO-News
subscribers.

I would like to bring to your attention a certain observation I made
regarding the 1999 Leonids meteor shower, to which I would kindly ask your
comments.

I took successive pictures of the event as of 11:30UT on November 17 until
about 03:00UT on November 18, 17 altogether. Each picture was taken by
exposing the ASA 400 film for 8 to 12 minutes. The camera used had a 50-mm
f/1.8 lens on it. When the processed film returned from the photo shop it
turned out that the camera lens was not set to infinity, as a result of
which all pictures are out of focus.

I remember that a few years ago (three maybe) there was an article in Sky &
Telescope magazine (by David Malin of the Anglo-Australian if I am not
wrong) about using a special technique for deriving the true colors of
stars. His technique called upon de-focusing the telescope in stages and
recording the image of a star on color film, resulting in a fan shaped
image of the star that reveals its true color.

Keeping that in mind, and having all my pictures of the Leonids meteor
shower unfocused, I revisited the photos. And, although they are
aesthetically unpleasing, the pictures might yield an interesting
scientific fact.

As it turns out, all meteor trails up to a certain time have a distinct
deep red-purple color. From that time on, they all have green-blue color.
As I took the pictures in succession all through the night, this fact is
evident.

Ruling out atmospheric extinction as the reason for this color difference,
it is left to surmise that there was a distinct compositional difference
between the meteorid material that hit the earth first, later being
replaced by different type of material. This might correspond to
Asher-McNaught's prediction that at the nodal crossing at 01:54UT the Earth
will hit fresh, one revolution material, while the peak at 02:08UT will be
from three revolution (100 years old) material.

I don't have enough meteors on my film to make it a rule. Are there any
other photographers having the same effect on their film?

Although I have noted meteor color differentiation in pictures taken by
others (Juan Carlos Casado of Spain is just one), I have to be very
cautious, though, and provide ample reservations as to my observation,
since it is based on a very small sample and as such can be highly biased.

Best regards,

Ilan Manulis

Head of the Small Solar System Objects Section
The Israeli Astronomical Association

------- End of Forwarded Message


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