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November 17, 1999: Tuesday night, on an Illinois highway
east of Chicago, traffic slowed to a crawl as motorists peered
at an extraordinary fireball blazing overhead. "It was of the most beautiful meteors I have ever seen," said Jamie Dresser, who was driving home from work just after 6 pm CST. "It was so bright that it lit up the sky for quite a distance. There was a blue corona ... and it was actually trailing fire for quite a distance. I sincerely look forward to driving home the next few nights!" Above: The above 533 KB QuickTime simulation illustrates the relationship during the Leonids meteor shower between the earth, comet Tempel-Tuttle's dust field, and the constellation of Leo. The size of the earth and sun have been exaggerated for clarity. When the earth passes through Tempel-Tuttle's dust field every November 17-18, the dust particles stream into our atmosphere and burn up as meteors. The red arrow during the simulation indicates that a ground-based observer would perceive the meteors as coming from a point (called the "radiant") within Leo, hence the name Leonids. [click for animation]
Tuesday night's fireball was so bright that it was first noticed by many observers while they were inside brightly lit buildings. "I was sitting in a Wendy's facing outside and saw the bright orange light in the sky," recounts Wendi S. Abbott of Cincinnati, OH. "I have no idea how long it lasted, but I had time to jump up, race over to the window and ask the family sitting there if they were seeing what I was seeing. The father said it was just a reflection in the window, but quickly changed his mind. It finally broke apart in about 3 or 4 pieces before it died out. What an incredible sight! If this is any indication of what's to come, this will definitely be a 'once in a lifetime [experience]'."
The trajectory of the fireball was similar in appearance to an aircraft, flying low and level across the horizon from west to east. Many observers reported seeing the meteor fragment into many iridescent pieces that traveled in a line like a string of Christmas lights. Below: This 400 KB QuickTime simulation illustrates the orbits of comet Tempel-Tuttle, Earth, and Jupiter from 1997-1999. The motion of the comet and planets are correct but their sizes have been exaggerated for clarity. Comet Tempel-Tuttle orbits the sun every 33 years and most recently passed near Earth in spring 1998. Like all comets, Temple-Tuttle is composed of ice and dust. As the sun slowly melts the ice, the comet's dust breaks off and spreads along the orbital path. Earth passes through Tempel-Tuttle's orbital dust field every November 17-18, causing the Leonids meteor shower. [click for animation]  Could
this be a taste of things to come in the next 24 hours? Possibly.
The Leonid meteor shower is expected to peak this Thursday morning
when the Earth slices through the debris stream of comet Tempel-Tuttle
around 0200 UT on November 18. Last year a shower of Leonid fireballs
(meteors brighter than magnitude -3) dazzled observers in Europe
and the Americas. In 1999 many experts anticipate an even better
show. No matter where you live, the best time to watch will be
between midnight and dawn on Thursday. On Wednesday evening,
November 17, before the constellation Leo rises, star gazers
could be treated to more Earth grazers as Leonid meteoroids arc
over the horizon. With the Leonids just around the corner, it may seem surprising that Tuesday's fireball was probably not a Leonid. Leonid meteors emanate from a point in the sky within the constellation Leo, which rises above the eastern horizon around midnight. At the time of the fireball sighting Leo was about 35 degrees below the northern horizon, which means that Leonid Earth-skimmers appearing over the horizon would travel roughly north to south. Most observers reported that the November 16 fireball moved west to east. While it is possible that this meteoroid was a part of the debris stream of comet Tempel-Tuttle (the parent of the Leonids), it is far more likely to be an unrelated, sporadic meteor or perhaps a piece of "space junk" decaying from low-Earth orbit.  Right: Not every meteor in November
is a Leonid. This video clip, recorded by Dr. Tony Phillips at
5 a.m. PST on November 16, 1999 shows two meteors slicing through
the constellation Orion. The brighter, fast moving meteor that
flashes downward by Orion's shoulder is a Leonid. Tracing the
meteor's path backward leads to the constellation Leo (off the
screen). A second, slower-moving meteor emanating from Orion's
sword is a Taurid, a minor shower that is active at the same
time as the Leonids. This meteor comes from the direction of
the constellation Taurus.Whatever this fireball was, observers around the world have been seeing genuine Leonids for over 24 hours. The Leonids Environment Operations Center at the NASA/Marshall Space Flight Center is managing data from a global network of observers coordinated by the US Air Force and the University of Western Ontario. Since early Tuesday morning trained spotters have filed reports of 8 to 86 meteors per hour (ZHR). In most years, 86 meteors per hour would be considered a substantial shower, but this could be the year for a full-fledged Leonids storm. Only time will tell if predictions of more than 1000 meteors per hour will come true. One thing is sure, the place to be before dawn on Thursday morning, November 18, is outdoors and looking up! For more information about how to view the Leonids and submitting data to NASA, click here. |
| Web Links |
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Leonids Live! -site of the live webcast of the 1999 Leonids North American Meteor Network - home page Related Stories: Perseids
Live! Balloon Flight Planned
-- Aug 6, 1999. A NASA weather balloon will ascend to the stratosphere
for a live webcast of the 1999 Perseids. |
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