Leonids
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Watch for "Falling Stars" Next Monday Night - 16 November 1998

+ Von Del Chamberlain +

November 11, 1998

"Shooting stars like snowflakes in a storm." That was the phrase used by Oglala Teton Indians of the American Plains to name the year that other Plains Indians called, "Storm of Stars Winter," "Winter of the Falling Stars," and similar names. One record stated that the Kiowa...were wakened by a sudden light. Running out from the tipis, they found the night as bright as day, with a myriad of meteors darting about in the sky. The parents aroused the children, saying, "Get up, get up, there is something awful going on." They had never before known such an occurrence, and regarded it as something ominous or dangerous, and sat watching it with dread and apprehension until daylight.

Many and vivid are the descriptions of the greatest meteor blizzard in human memory. It took place on the night of November 12-13 of the year 1833. It might happen again either in 1998 or 1999. Indeed, even though it hasn't happened yet, it is being called the major astronomical event of 1998.

The meteor storm of 1833 was observed with great interest by some and prodigious concern by others. There were predictions of both dire and sublime consequences, and some saw the event as having important religious symbolism. The Mormon prophet Joseph Smith wrote: I arose, and to my great joy, beheld the stars fall from heaven like a shower of hailstones; a literal fulfillment of the word of God, as recorded in the Holy Scriptures, and a sure sign that the coming of Christ is close at hand. In the midst of this shower of fire, I was led to exclaim, "How marvelous are Thy works, O Lord! I thank Thee for thy mercy unto Thy servant; save me in Thy kingdom for Christ's sake."

This memorable event marked the beginning of scientific study of meteors. Even though one can go out on any dark, clear night and see a few meteors every hour, up until 1833 it was thought that they were caused by some strange atmospheric phenomenon, perhaps electrical, chemical or even spiritual. But as the world watched on that blazing night, it was noted that the meteors seemed to stream in from a point in the sky located in the constellation Leo, and scientists observed that during the hours the meteor storm lasted this "radiant" moved with the stars, remaining constantly in Leo. Thus, they reasoned, the effect must be caused by particles flowing in from space, seeming to radiate from Leo like any other parallel lines converging to a point in the distance.

Agnes Clerke, a historian of astronomy, attempted to describe this remarkable event: On the night of November 12, 1833, a tempest of falling stars broke over the Earth...the sky was scored in every direction with shining tracks and illuminated with majestic fireballs. At Boston, the frequency of meteors was estimated to be about half that of flakes of snow in an average snowstorm. Their numbers...were quite beyond counting; but as it waned, a reckoning was attempted, from which it was computed, on the basis of that much-diminished rate, that 240,000 must have been visible during the nine hours they continued to fall.

Once the 1833 shower had been scientifically studied, scholars looked back in history and found that impressive showers had taken place in November many times in the past and this led to realization that the Leonids tended to be intense about every 33 years, with some exceptions. The storm of 1833 was apparently the most spectacular of all, but notable ones had taken place in 1799, 1533, 1366, 1202, 1037, 967, 934 and 902. The most recent Leonid shower of note was on November 17, 1966 when a tremendous meteor storm was observed for upwards to an hour from the central and western United States.

The source of Leonid meteoroids, as the particles themselves are called, has been found to be a comet known as Comet 55P/Tempel-Tuttle. This comet travels in an elliptical orbit with period of 33.2 years. Sunlight evaporates gases and liberates particles from the comet. Each ejected particle has its own orbit round the Sun and each is effected by gravity of other bodies passing near it. Over time, a river of particles has been spread out more or less along the comet's orbit. The closer the comet is to the Sun the more particles it releases. Thus, it has been learned, our greatest Leonid showers take place in years close to when Comet 55P/Tempel-Tuttle reaches the point in its orbit nearest the Sun. This happened early in 1998. And the shower reaches its peak when Earth crosses through the plane of the comet's orbit.

Scientists devoting their professional lives to meteors, meteor showers and related topics are excited at the possibility of a great Leonid storm in either or both of 1998 and 1999. What can they tell us about our chances of observing the Leonid storm again? The first thing they tell us is that prediction of the details of a meteor shower is an uncertain business. They know that the stream of particles is spread out along a path in space related to the orbit of Comet 55P/Tempel-Tuttle. They know that Earth moves through some part of this stream of particles in November every year. They know that most years we go through a very weak part of the stream and only a few meteors are visible to a single observer each hour. They know that we encounter more particles along this "cosmic gravelbed" every 33 years when the "cosmic litterbug" has recently passed near us, and that this is likely in 1998 and 1999. They know that Earth will cross through the plane of the orbit of Comet 55P/Tempel-Tuttle about 1:00 p.m. MST, November 17 this year. Finally, they know that a number of factors control the particle stream, and this is the part that makes accurate prediction of the shower difficult.

The law of gravity is the major problem. Every object of the universe attracts every other object with a force which is stronger the more massive the objects and the closer they are to each other. Whenever anything passes close enough to the stream of Leonid meteoroids, gravity gives them a significant nudge. There are so many objects available in the solar system, most notable the giant planets Jupiter and Saturn, that the problem of precise tracking of the meteoroid stream is very complicated. In order to have a meteor blizzard like the one in 1833 we must encounter a dense knot within the stream. But if we miss the major concentration, even by a small amount, the shower will not be very intense. If we do pass through a swarm of meteoroids in November 1998 or 1999, those watching under clear skies will be treated to one of nature's most spectacular events.

When will the storm of light take place, if it does come? The best prediction is that it will happen when Earth crosses through the orbital plane of Comet 55P/Tempel-Tuttle about midday, Mountain Time, on the date of November 17 this year. If that turns out to be accurate, we will miss the main event in the United States. The prediction is that the storm will be best observed from eastern Mongolia and northeastern China. Keep in mind, however, that such predictions are filled with problems and that the storm could take place during dark hours here in America.

So will it occur, or won't it? No one knows for sure. Each person will have to decide whether they are willing to stay up and watch all night--preferable both on the nights of November 16-17 and November 17-18--or whether they would rather have the usual good night sleep with the possibility of learning later that they missed one of the opportunities of their lifetime. In 1878 historian R. M. Devens listed the 1833 Leonid shower as one of the 100 most memorable events in U.S. history.

The way to watch a meteor shower is to bundle up in warm clothing at a place with a great view of the sky, away from city lights, and simply lie back on a lawn chair or sleeping bag and look up. You are likely to see more meteors after midnight when the constellation Leo has risen into the sky. Neither telescopes nor binoculars are needed. In fact, it is best to focus on some region of the sky with just your eyes. If you are especially anxious to attempt to experience the storm, you should carefully consider the weather; since it might be cloudy on particular nights, you might want to take advantage of any clear nights starting as early as Saturday night, November 14 and continuing through Tuesday night, November 17. You might also seek the most up to date information from local observatories, planetariums and from the Internet.

Next Monday or Tuesday night we might have a meteor shower. We might have a meteor storm. We might have a meteor blizzard. We might have a meteor drizzle, or we might have a meteor fizzle. If the storm doesn't come this year, it might happen next November, so stay tuned.

Readers of this column might find interesting memories of the 1833 Leonid meteor shower recorded in journals dating to that time. Mr. Chamberlain would be grateful for the opportunity of receiving copy of any such accounts.

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