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Re: (meteorobs) A huge meteor dazzles the Yukon



Hi!!

The Lemke series of images is quite interesting.  Since the colors are due
to the color of the illuminating dawn light you can infer some
three-dimensional geometry from them, the redder parts of the dust cloud
being lower and the whiter parts being higher.  The central two images of
the set of four adjacent images show this very nicely, with color at the
lower right end of the cloud being blue-white, already in full illumination
by the Sun well above the apparent horizon and therefore illuminated by
essentially unreddened light, with a progression in color  all the way to
deep red at the upper left which is at considerably lower altitude and just
beginning to be illuminated by the deeply reddened light of the just rising
Sun as seen from that point in the dust cloud.  In the final image, cirrus
clouds are beginning to be illuminated by their local just rising Sun.
Comparing this last image with the others, the brightest red spot in the
cirrus clouds is roughly comparable to the red of the reddest part of the
dust cloud imaged in the second or third images of the overall sequence,
implying that the bottom end of the dust cloud experienced the same phase
of sunrise as the local cirrus clouds about 40 minutes earlier.   Given the
latitude of the observer and the declination of the Sun this reduces to a
nice little geometry problem to determine the height of the lower end-point
of the dust cloud.  One would also need the direction the camera was
pointed and some information on exposure and image scale in order to
iterate to a really good self-consistent solution.  A photometric analysis
of the colors of the cloud in a given image could take the assessment a
step farther and give reasonable estimates of heights above sea-level at
different points in the cloud.  This would be fun to play with for anyone,
such as myself, who was so inclined.  If anyone is doing this, please let
us all know what you find, and if not I'll run some numbers on it and let
you know what they say.

Clear Skies Everyone 

Jim Wray

-------------------




At 04:38 PM 1/25/00 +0000, you wrote:
>http://spacescience.com/headlines/y2000/ast25jan_1.htm                  
>     Space     Science News home           Yukon Meteor Blast
>
>      A thunderous meteor streaked over the Yukon last     week. Now a NASA
>airplane has flown through the debris cloud     in search of
>extraterrestrial particles.
>
>                     January 25, 2000 -- Last week,     one of the most
>dramatic meteors in 10 years streaked across     the skies of the Yukon
>Territory in Canada. Witnesses reported     two sonic booms, a foul odor,
>and sizzling sounds heard all the     way from Alaska through northwestern
>Canada. Based on readings     from defense satellites and seismic
>monitoring stations, scientists     estimate that the meteor detonated with
>the energy of two to     three kilotons of TNT. 
> 
>     Above: This sequence of pictures     was captured by Ewald Lemke
>(Atlin     Realty, Atlin, British Columbia). It shows the expanding    
>smoke train of the Yukon meteor over a 14 minute period. The     first
>frame shows a smoky red vapor trail just 1 minute and 30     seconds after
>the initial flash. 
> 
>                              
>         Sign up for         our EXPRESS SCIENCE NEWS delivery
"""" 
> 
>     There was no major meteor shower on January 18. The Yukon fireball    
>was probably what astronomers call a sporadic meteor.     The inner solar
>system is filled with tiny dust particles that     have bubbled off
>innumerable comets as they pass close to the     Sun. These particles,
>called meteoroids, hit the Earth from random     directions producing 2 or
>3 sporadic meteors per hour every night. 
> 
>     Scientists from NASA and the Department of Defense are interested    
>in the the Yukon event. Samples of dust or rock fragments from     the
>explosion could reveal the origin of the meteoroid. Defense     specialists
>would also like to know what the meteoroid was made     of to help
>calibrate the sensors they used to detect the fireball. 
> 
>      On Friday, January 21 -- just three days     after the explosion --
>an Airborne Sciences ER-2 aircraft from     NASA's Dryden Flight Research
>Center flew to the Yukon Territory     of northwestern Canada in an effort
>to collect atmospheric samples     of the meteor's lingering debris trail.
>The region, near the     town of Carcross, is mostly unpopulated. 
> 
>     Left: The Airborne Science ER-2     aircraft are platforms for a
>variety of high-altitude science     missions. They are used for earth
>science and atmospheric sensor     research and development, satellite
>calibration and data validation,     and now for catching meteoroids. 
> 
>     Scientists gathered samples of the debris cloud at an altitude     of
>65,000 feet with an instrument called the Aerosol Particulate     Sampler
>(APS). The APS is a system of two small five-inch by     four-inch paddles
>that deploy simultaneously from the ER-2's     left wingtip. The paddles
>are coated with a silicon oil that     collects particles from the high
>altitude air stream. After a     period of exposure, the paddles are
>withdrawn into hermetic enclosures     that prevent contamination during
>the aircraft's return to Dryden.     The paddles will be removed and sent
>to NASA's Johnson Space     Center in Houston, Texas for analysis. 
> 
>     The ER-2 also carried a camera capable of taking black and white    
>photos of eight-mile wide swaths of the region in an effort to     locate
>any impact craters and other scarring of the earth, such     as flattened
>areas of forest, that may have been caused by the     explosion and impact
>of meteorites that separated from the meteor. 
> 
>      On June 30, 1908,     a huge explosion occurred in the sky above the
>central Siberian     wilderness near the Tunguska River in Russia. The
>concussion     from the blast, estimated at 20 megatons of TNT, leveled
>trees     in an area nearly 40 miles in diameter. Oddly, the explosion    
>produced no crater or other evidence of impact. 
> 
>     Right: Trees were incinerated in     a 9-mile (14.4 km) radius from
>ground zero and were knocked over     in a 25 mile (40 km) radius following
>the Tunguska explosion     in 1908. If this had occurred over a heavily
>populated area,     the effect would have been catastrophic for the people
>living     there. Image Credit: Smithsonian Institution. 
> 
>     Scientists at NASA and the University of Wisconsin conducted     a
>computer simulation that strongly suggests that the Tunguska     culprit
>was an asteroid, the most common class of meteorite.     The simulation
>indicated that an asteroid about 100 feet in diameter     and moving at a
>speed of 10 miles per second would disintegrate     at a height of about
>five miles above the ground - approximately     the same altitude at which
>the Tunguska object is believed to     have exploded. Information gleaned
>from the January 18 meteorite     in Canada might enhance understanding of
>the Tunguska event.    
> 
>              Web Links                 NASA     DRYDEN PARTICIPATING IN
>METEOR EVENT DATA COLLECTION -Dryden Flight Research Center     Press
>Release      Huge Fireball Dazzles Midwest -Thousands of people across    
>the Eastern US saw a brilliant fireball streak across the night     sky
>just 24 hours before the 1999 Leonids. (November 17, 1999)      Frequently
>Asked Questions about Fireballs -from the American Meteor     Society      
>            
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>related         to breaking science news, please visit Thursday's        
>Classroom                   Editor: Dr.         Tony Phillips 
>         Author: Dr. Tony         Phillips                      

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