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(meteorobs) IMO-NEWS: "wild claims about the hail of mini-comets"




From: dfischer@astro.uni-bonndot de (Daniel Fischer)
To: imo-news@imodot net
Subject: The wild claims about the hail of mini-comets

I'm sure that most in the meteor community have by now heard about the
revival of the ideas about the hail of 10 m sized and highly unusual
comets that supposedly hit the Earth's atmosphere every few minutes. At

http://smallcomets.physics.uiowadot edu

discoverer L. Frank himself tells the story, while various stories e.g. at

http://www.sciencenow.org/html/970528b.htm ,
http://www.sciencenews.org/sn_arc97/5_31_97/fob1.htm  and
http://washingtonpost.com:80/wp-srv/WPlate/1997-06/01/117L-060197-idx.html

also give weight to the highly controversial nature of the claims. 


What puzzled me most was a picture released last week, e.g. at

http://smallcomets.physics.uiowadot edu/www/may28-2.html and
ftp://pao.gsfc.nasadot gov/pub/pao/releases/1997/97-61.jpg

that, according to the caption, "contains the trail of an object
over the Atlantic Ocean and Western Europe on Sept. 26,1996. The object
was in sunlight but the Earth below was in darkness, so a map of the
Earth has been superposed onto the image as a frame of reference.
According to Dr. Louis A. Frank of the University of Iowa, the instrumens
principal investigator, this time lapse image with a duration of 54
seconds shows a small comet the size of a two-bedroom house
that disrupted 5,000 to 15,000 miles above the Earth."

In his own description of the image Frank calls it a "spectacular
disruption (at right) of a small comet the size of a two-bedroom house
[that] took place 5,000 to 15,000 miles above the Atlantic Ocean at 2228 UT
on September 26, 1996. A view of Earth at the time of the event has been
superposed onto the far-ultraviolet image as a frame of reference. This
unusually bright and long-lived trail, which was captured by Earth Camera
aboard NASA's Polar spacecraft, ends over Germany."

Germany, at 22:28 UTC? That means it was already dark! Which leads to the
immediate question: Did anyone observe something unusual on that Sept. 26,
1996, evening over the British Isles or Central Europe - or did meteor
cameras record something unusual? From the otherwise undocumented image
itself it is impossible to judge the luminosity (let alone the visual
brightness) of the phenomenon, but its visual observation (or clear null
result) would be an important constraint for the physics involved.


Another interesting note for amateur observers: In his new "FAQ" list at

http://smallcomets.physics.uiowadot edu/www/faq.htmlx

Frank also addresses amateur astronomy and visual observers twice:

"Can the small comets be seen by the naked eye? 

Yes, but you will need lots of patience--and a little luck. Too see a small
comet you must stand out on a clear dark night until you see a short streak
that quickly snuffs out. It will be about the brightness of Venus for about
two seconds before it vanishes. But you will have to be out there for a
hundred hours or so to see one. A hundred hours of clear night viewing
does not happen often in the average lifetime. 

How can amateur astronomers spot the small comets? 

Amateur astronomers whose telescopes have mirrors or lenses
measuring12 inches or larger should be able to sight the small comets.
During the course of a day there are two times for observation, each about
one or two hours long. One ends about 45 minutes before sunrise; the other
begins about 45 minutes after sunset. The small comets will be seen at a
distance about 2,500 to 4,500 miles from the observer,so the telescope
should be pointed in such a way that it is looking for them at these
distances, just outside the Earth's shadow. Inside the shadow the objects are
not illuminated by the Sun and are invisible. Every two hours or so a small,
quite dim object will slowly move across your view, as long as your field of
view is about four times the size of the Moon. The object will move at a
distance equal to the Moon's diameter every five seconds or so. Several
amateur astronomers have reported seeing such objects." 


Comments on this remarkable issue - and Frank's wild claims in the last two
paragraphs in particular - would be highly welcome, especially since I am
right now writing a review article about it!


Daniel Fischer, dfischer@astro.uni-bonndot de

http://www.geocities.com/CapeCanaveral/5599/mirror.html