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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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> Author: Dr. Tony Phillips
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