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Fire in the sky.

Few celestial events are as memorable as a brilliant meteor. Judging by the reports received at Sky & Telescope, the intense media coverage of Comet Shoemaker-Levy 9's impact with Jupiter in July 1994 appears to have sensitized the public to celestial visitors of all kinds. Some recent meteor-related events have been so striking, however, that they have captured national headlines in their own right.

TSUKUBA BOLIDE AWES JAPAN

The most spectacular daylight bolide in recent Japanese memory occurred on the afternoon of January 7th (7:21 Universal Time). Many thousands witnessed the reddish, -12-magnitude fireball as it streaked across the sky from Yokohama to Tokyo and exploded at a height of 8 kilometers. Seconds later student Ryutaro Araki stopped to retrieve a still-warm stone that had fallen in front of his car near Tsukuba, 38 kilometers northeast of Tokyo. Another chunk put a clean, round hole in the roof of a garage near the city.

Sky & Telescope contributing photographer Akira Fujii witnessed the aerial aftermath from Chiro Memorial Observatory in Koriyama, 90 km northwest of Tsukuba. Fujii photographed the smoke trail that hovered in an otherwise cloudless sky for more than an hour (see the photographs, opposite). The white trail was still visible as search teams organized by Chiro and the National Museum combed a wide swath of ground around Tsukuba. More than 40 meteorite fragments were eventually recovered, the largest weighing 170 grams.

Masako Shima (National Science Museum of Japan) examined the recovered meteorites and found them to be material from a stony chondrite, weighing an estimated 0.8 kilogram before its fiery plunge through the atmosphere. Her measurements of cosmic-ray-induced isotope changes reveal that the meteorite separated from its asteroid "mother" about 19 million years ago. The object was traveling approximately 16 km per second at a roughly 40 [degrees] angle to the ground when it exploded. Ongoing analysis of seismometer readings of the meteor's sonic boom are expected to refine the trajectory. Preliminary calculations by Suichi Nakano point to an orbit with an aphelion in the asteroid belt somewhat beyond the midpoint between the orbits of Mars and Jupiter.

Analysis shows the fragments to be a mix of iron-rich olivine and related minerals in a matrix called breccia. Although this is a common type of stony meteorite, such chondrites are rarely found, since they quickly weather to resemble terrestrial rocks. Thus, an observed fall is an excellent scientific opportunity.

Meteor collectors will take little joy in the fact that no material from the fall is currently available. According to meteorite dealers Ronald Farrell and Robert Haag, all the collected fragments are safely esconced in the National Museum, which has no plans of releasing them.

FIREBALLS GALORE

A bluish white bolide - brighter than magnitude -11 by many accounts crossed the northern tier of states from Pennsylvania to the Midwest last August 25th. First sightings reported to the media and the National Weather Service were from Philadephia and upstate New York. The brilliant meteor's glowing orange train terminated in a dazzling flash over Windsor, Ontario, around 12:40 a.m. local time. The meteor was so bright that it was seen through clouds at the Starfest convention near Mount Forest, Ontario, about 250 km away.

Frank Shepley of the Royal Astronomical Society of Canada's Windsor Centre reports that alarmed residents believed the bolide had impacted, destroying a trailer on the edge of town. North American news media echoed versions of the story, with major network reports adding that a "basketball-size object" had been recovered from the wreckage. However, geologist Peter Hudek (University of Windsor), who investigated the burned-out hulk, told Sky & Telescope that he had found no sign of an impact or meteoritic material, putting the fiery incident down to pure coincidence. Peter Brown of the International Meteor Organization (IMO) later reported that the endpoint for the fireball was south and perhaps east of Lake Erie, taking any possible recovered material out of Canadian territory.

An early morning apparition was reported from Louisiana to eastern Mississippi on January 13th. Bob Abraham of northwestern Louisiana's Shreveport Astronomical Society was fueling a Federal Express aircraft before dawn when "the whole place lit up like daylight." Fears of exploding fuel were allayed when he and the plane's crew looked up to see a fireball "bigger and brighter than the full Moon" north of Procyon. The meteor traveled eastward across the zenith for a few seconds, ending in a brilliant flash near the position of galaxies Messier 65 and 66 in Leo.

Louisiana electrical worker Joseph Cotten, his son, and a companion were duck hunting when the meteor passed overhead, leaving a smoke trail that persisted for several minutes across a third of the sky. Cotten likened the terminal flash to the arcing of a high-voltage electrical line. Reports from other hunters in the region stated that the bluish green meteor lit up the ground more brightly than their krypton-bulb flashlights. Around 5:45 a.m. CST John H. Oldshue of Columbus, Mississippi, saw the sky pale as the meteor disappeared below his western horizon. Further confirmation came from radio meteor observer Thomas Ashcraft in New Mexico, who recorded an event beginning shortly after 5:44 a.m. CST.

Charles Sawyer of Pembroke, Maine, saw a "once-in-a-lifetime" -10-magnitude bolide on September 3, 1995, that changed from brilliant blue-white to orange, ending with a snapping sound. Other fireball sightings include numerous displays connected with major showers. "The night sky never ceases to amaze" Maurice Bertrand of Travis Air Force Base in California. He witnessed a brilliant seconds-long Leonid on the morning of last November 18th that lit up the desert and left a smoky train glowing in the light of the crescent Moon.

The Fireball Data Center of the International Meteor Organization in Dusseldorf, Germany, receives many reports of fireballs exceeding magnitude -6, such as the blazing behemoth on the 6th of August over Tawa, New Zealand, that may have reached -14. A -12-magnitude object crossing over Washington State the same month emitted a simultaneous crashing sound heard by two observers. While this is tantalizing stuff for meteorite hunters, no recoveries of observed falls were made in North America last year. Those wishing to make official fireball reports have several options (see page 97). Sky & Telescope is also happy to receive reports of extremely bright meteors.

The next time you are at a star party and hear the familiar "Wow! Look at that one!" consider reporting the event. Your data could help determine the object's trajectory and orbit.

RELATED ARTICLE: How to Report a Fireball

Report fireball sightings in North America to Robert Hawkes of the Meteorites and Impacts Advisory Centre (MIAC), e-mail: rhawkes@ mta.ca, or by mail to Canadian Fireball Centre (MIAC), Dept. of Physics, Mount Allison University, Sackville, New Brunswick, E0A 3C0, Canada.

Andre Knoefel of the International Meteor Organization's Fireball Data Center (FIDAC) in Dusseldorf, Germany, takes international reports by e-mail at starex@tron.gun.de or by telephone (answering machine) at 49-211-450-719. As with any astronomical report, your information has more value when it is exact. For fireballs give the exact observing location, date and time, direction, speed, brightness, color, and any associated sounds, with your name and contact information. Full details on proper reporting may be found on FIDAC's World Wide Web site at http://www.tu.chemnitz.de/smo/imo/fireball/fireball.html.
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Title Annotation:Observer's Page; includes related article; brilliant meteors
Author:Pepin, M. Barlow
Publication:Sky & Telescope
Date:May 1, 1996
Words:1225
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