Leonid meteor storms
Every 33 years a small comet appears in the innermost parts of our solar system. This comet moves in an orbit around the sun that brings the comet occasionally near the orbit of the earth. During the passage through the inner parts of our solar system, the comet is heated by the sun. A comet consists mainly of frozen water, gases and dust. As the water and gasses evaporates, dust particles are released and move in almost the same orbit as the comet around the sun. Over time, the dust spread along the entire path of the comet. As a result, each year when the Earth is near the comet's orbit the dust particles (also called meteoroíds) in that orbit collides with the earth's atmosphere. As seen from earth they are visible as shooting stars (or better: meteors). The meteors from the comet 55P/Tempel-Tuttle are visible from November 5 to 25. The earth passes through the densest parts of this meteorshower around 17 or 18 November.


Figure 1: Orbit of comet 55P/Tempel-Tuttle in our solar system.


Figure 2: the radiant of the Leonids lies in the constellation of Leo (Lion)

Because the dust particles plunge parallel into the earth's atmosphere, you'll have the impression that the meteors are coming from one point in the sky. It is a perspective effect comparable with train rails. It seems like the train rails converge on the horizon. This point in the sky is called the radiant. Meteors from the comet 55P/Tempel-Tuttle have their radiant in the constellation of Lion, whose Latin name is Leo. So the meteors belonging to comet 55P/Tempel-Tuttle are therefore called Leonids.
If the comet is far away the numbers of Leonids remains to be low, one can count up to 15 per hour. However, if the comet comes closer to the sun the density of the dust trails increases and also a new dust trail is formed due by the heating of the comet's surface. Usually a number of years before and after the perihelion of the comet (perihelion is the time when the comet is closest to the sun) larger quantities of meteors can be seen. The numbers of meteors then rise from 30 into thousands an hour! In the latter case one speaks of a meteor storm. This is the ultimate phenomenon for meteor observers to witness. Below some examples of dust trails in the wake of comets. Another fine example of a young dust trail see http://www.astrosurf.com/obsdauban/images/cometes_img/10P/mosa025.jpg


Figure 3: Image of the comet 1P/Halley taken by the Giotto spaceship (ESA).
Clearly visible are the fontains of dust. Here we look at the birth of the Orionid meteor stream. Image credits: ESA.


Figure 4: Image taken with the IRAS satellite. Here we look at a dust trail of Comet Gunn.
Comet Gunn is visisble as a big doth in the left uppercorner of this image. Photo credits: IRAS/ESA


Figure 5: another example of two dust trails: below a dust trail of Comet Tempel 2 (the comet stands 3 degrees outside the image) and above a dust trail of Comet Encke (the comet stands 6 degrees outside this image). If the earth moves through such a dust trail, a meteor storm will occur. Image credits: IRAS/ESA

Historical Leonid meteor storms


Figure 6: Alexander von Humboldt and Aimé Bonpland observing the Leonid meteor storm of 1899 in Venezuela. Note that at that time the people had no idea of the phenomenon that the meteors seems te come from a point at the sky, the radiant. Picture credits: unknown.


Figure 7: famous wood-cut made by John Couch Adams (?) of the Leonids of 12/13 november 1799 as seen from Cape Florida.


Figure 8: in 1799 the earth encountered dust trails of 1600, 1400-1567, 1135-1333, 604-1102 from the comet 55P/Tempel-Tuttle (Meteors Showers and Their parent Comets, Jenniskens P., 2006). The old dust trails contains larger particles causing more brighter meteors. This was particularly favorable in 1799 because there was a full moon in the sky (in the constellation Aries). Picture credits: Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE).


Figure 9: engraving of the Leonids 1833 from Bible Readings for the Home Circle, made in 1888, courtesy of sdapillars.org..


Figure 10: from Erik Arnesen, Oslo: A Critical Look at our Godless Society.
Clearly to see on this picture is that the people are afraid of what they see. They thought that the end of time was near. Picture credits: unknown.


Figure 11: Leonid meteor storm over Niagara Falls, 1833. Picture credits: unknown.


Figure 12: Another fine drawing of the Leonid meteor storm of 1833 above the Niagara falls. Picture Credits: unknown.


Figure 13: Leonid meteor storm on November 12/13, 1833 over North America. The strange trails remainded the author of the persistent trains he observed at Delingha Radio Observatory during the Leonid Fireball shower of 1998. So the hooked or curved shapes are not the Leonid meteors, but maybe showing the persistent trains. Image credits: unknown.


Figure 14: Developement of a persistant train after a bright Leonid fireball. See the similarities with Figure 13
Image credits: IMO.


Figure 15: Illustration of the Leonid meteor storm of 1833 in a local newspaper. Picture credits: unknown.


Figure 16: in 1833 the earth encountered dust trails from 1800 and 1767
of comet 55P/Tempel-Tuttle resulting in a major meteor storm (Meteor Showers and Their Parent Comets, Jenniskens P., 2006). Picture credits: Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE).


Figure 17: the Leonid meteor storm of 1866 above Greenwich. Picture credits: Sun, Moon and Stars by Agnes Giberne. London, 1884


Figure 18: in 1866 the earth encountered a dust trail from 1833 of Comet 55P/Tempel-Tuttle, resulting in a major meteor storm with a calculated ZHR of 6800 ~1100 (Meteor Showers and Their Parent Comets, Jenniskens P., 2006).
Picture credits: Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE).


Figure 19: in 1899 no dust trail encounters, all dusttrails lies inside Earth's orbit.
Picture credits: Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE).


Figure 20: also in 1933 no dust trail encounters. However, elevated Leonid activity is reported from Egypt and the US.
Picture credits: Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE).


Figure 21: famous picture of James W. Young taken at Table Mountain Observatory during the Leonid meteor storm of 1966. The 3 minute exposures were taken with Kodak Plus-X 35mm film using a Zeiss-Ikon camera, with a 35mm f/2 wide-angle lens, using a simple camera tripod. Photo's courtesy TMO/JPL/NASA.


Figure 22: another great picture taken by James W. Young of a bright Leonid fireball and a persistent train of another Leonid fireball. The 3 minute exposures were taken with Kodak Plus-X 35mm film using a Zeiss-Ikon camera, with a 35mm f/2 wide-angle lens, using a simple camera tripod. Photo's courtesy TMO/JPL/NASA.


Figure 23: very bright Leonid fireball of magnitude -10 and three weak Leonids.
The 3 minute exposures were taken with Kodak Plus-X 35mm film using a Zeiss-Ikon camera, with a 35mm f/2 wide-angle lens, using a simple camera tripod. Photo's courtesy TMO/JPL/NASA.


Figure 24: Trails of meteors near the bowl of the Little Dipper, in a 10 to 12 minuteexposure by A. Scott Murrell during the 1966 Leonid storm. He used a 50-mm f/1.9lens and Tri-X film in a camera tracking the stars at New Mexico State University Observatory. Source: Sky & Telescope, November 1995, p. 30.


Figure 25: In 1966, the earth moved through two young dust trails of 55P/Tempel-Tuttle (from 1932 and 1899) which resulted in a huge meteor storm and ZHR's of 15000 ~3000. Picture credits: Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE).

The last Leonids season 1993-2009: my experiences
Shortly after the departure of my hobby in 1978 I read about the expected Leonid meteor storm in 1999. I was highly looking forward to this event and was hoping I could observe this rare phenomenon. At that time there was still little known about the behaviour of meteor streams and stream modelling.
The previous series of outbursts of the Leonid meteor shower occured in the period 1961-1972 (see above). So the first outburst of the new Leonid season was expected in 1993 or 1994 in progress for the real meteor storm that would possibly occur in November 1998 and/or 1999. The Leonids had their first outburst in 1994: ZHR 80-100 with many bright Leonids. At that same time there were several meteor astronomers active in the field of meteor stream modelling . Amongst them Kondrateva & Reznikov (80's), McNaught & Asher (90's), Lyytinen & van Flandern and Jenniskens & Vaubaillon. These predictions were getting better and more accurate and proved to be a major tool in organizing expeditions or last minute campaigns.
The newest models assume that every time the comet moves through the inner parts of our solar system a new trail of dust is shaped. Because the comet's dust(trails) are sensitive to planetary perturbations and and the gravitational and radiation pressure effects of the sun they have different positions. We now know that meteor storms do not necessarily have to appear at the node passage of the parent comet. And we also know that the effect of multiple dust trails as the comet is near perihelion, can result in multiple meteor storms in a short period of time. This happened in 2001 and 2002 when the earth encountered shortly after each other two dusttrails resulting in two meteor storms in rapid succession.


Figure 25: An overview of dust structures as a comet is near it perihelium.
Meteor outbursts occur when the earth moves througt the filament or a dusttrail.
Picture from Meteorshowers and their Parent Comets (2006) by Peter Jenniskens.

Well, writing this story in 2012 I can say I was lucky to see most of the Leonid outburst's in the period 1994-2009. Small ones, bigger one's and even two meteor storms (1999 and 2001). The links at the right of this page gives you reports and pictures of that years Leonids.
Finally a thank you to all the people I 've been on an expedition and to those who organized expeditions and possible.
Also many thanks to Michel Vandeputte and Peter Bus.
Enjoy!
Koen Miskotte

AstroRockers Blog

Leonid observations of Koen Miskotte

Meteorshowers

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eta Aquariids
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Leonids

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