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The most spectacular Leonid meteor shower of the 21st century
Tong Yun
1/7/2003



The most spectacular Leonid meteor shower of the 21st century appeared on November 17th through the 19th of this year. During the peak times of the meteor shower, as many as 10,000 trails of dusty debris swept past the sky every hour. The Beijing Planetarium in China observed two peak times, one at 4 A.M. on November the 18th and the other at 6:29 P.M. on the 19th. During the latter peak the rate was at 10,000 per hour, which is the highest peak rate of any Leonid storm in the 1990’s.

Meteors are better known as “shooting stars”; startling streaks of light that suddenly appear in the sky when a particle from outer space is incinerated high in the Earth’s atmosphere. We call the light phenomenon in the atmosphere a “meteor”, while the particle is called a “meteorite.” Between November 14th and 21st of every year, especially around November 17th, a larger number of meteors than usual originate from Leo. This is what is known as the Leonid meteor shower.

The Leonid meteor shower is directly related to a comet called Tempel-Tuttle.
The Leonid meteor showers occur at the same time each year because the orbits of Tempel-Tuttle’s dust and the Earth form a sort of celestial crossroads. Once a year, at the same point in space, the Earth goes through the crossroads. The number of meteors seen from that shower will depend on the amount of "traffic" at the time. Since the orbital period of comet Tempel-Tuttle is 33.2 years, there is a huge Leonid meteor storm approximately every 33.2 years lasting several years. A new round of Leonid meteor storms began at the end of the 1990’s, and it has peaked every November since 1998.

Now let’s look at the history of the Leonid meteor shower. As early as 1768 B.C., there were records of Leonid meteor showers found in China as well as other countries. South America had recorded Leonid meteor showers in 1799. In 1833, the Leonid meteor storm was very intense. A Boston observer described the phenomenon as follows: “On the night of November 12th-13th, 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.” (From Agnes Clerke’s Victorian Astronomy Writer)

In 1833, astronomers predicted that 33 years later, in November of 1866, people would be able to see a spectacular meteor storm. That prediction came true. That year Europeans observed meteors sweep across the sky at a rate of 5,000 per hour. In North America, people could see only 1,000 meteors per hour because the moon was too bright there. It was not nearly as spectacular as the shower of 1833. People waited for a Leonid meteor shower in 1899 with great anticipation but nothing happened that year. The year 1932 was also a huge disappointment. People saw only one meteor per minute. After repeated disappointments, people no longer eagerly anticipated Leonid meteor showers.

On November 17th of 1966, a Leonid meteor storm surged again. People in every corner of Arizona could see a tremendous storm of tens of thousands of meteors falling. The observed rates increased from about 100,000 per hour, to flurries of as much as 140,000 per hour. All of this happened within just 4 hours.

Bright meteors leave persistent glows. The afterglow in the path of bright fireballs lasts only a few seconds. This is known as the dust trail of meteors.

Just like “aliens from outer space,” meteor showers have brought people, especially astronomers, pleasant surprises and wonders. However, they are capable of bringing mankind catastrophes and destruction.

A closer look at the 200 gigantic meteorite pits on the Earth has revealed its wounded history. There is no telling how many “aliens from outer space” have hit the Earth and caused great disasters. It’s very difficult to determine since the traces of meteorites have been erased by geographical progressions and human civilizations.

In addition to the nine major planets, there are also many small bodies orbiting around the sun in our Solar System. The majority of them are located within a small body strait between Mars and Jupiter. Some of them have special orbits and pass close to the earth’s orbit on a regular basis, so they are called “near-earth bodies.” Some comets also cross the earth’s orbit. These types of bodies and comets are generally referred to as “near- earth celestial bodies.” If some of them were to collide with the earth, they would likely cause deadly disasters.

Sixty-five million years ago, a comet with a diameter of 10-20 kilometers hit the Yucatan peninsula in Mexico. The dust cloud from the collision remained in the sky for at least six months. During those six months the earth was in complete darkness. The collision was followed by a period of ten years of freezing cold temperatures. Various animals and plants became extinct during that time period. Many scientists believe that dinosaurs became extinct during that period of ten years.

In the early morning of June 30th, 1908 a great ball of fire swept across the sky in Siberia. When the fireball slammed into the atmosphere, it exploded and wiped out about 2,000 square kilometers of forest and burned a tremendous amount of trees. The impact from the explosion shook the earth atmosphere twice. This mysterious explosion is now known as the Tunguska explosion. People have proposed many different explanations about the explosion; everything from antimatter, a black hole, the crash of an alien’s spaceship, and so on. One of the explanations was that a meteor had hit the Earth. The meteor was composed of icy fragments and dust. It measured 100 meters in length and weighed a million tons. It hit the atmosphere at speeds around 30 kilometers per second and the impact from the explosion was 600 times more than the atomic bomb dropped on Hiroshima, Japan.

Near-earth celestial bodies with a diameter less than 50 meters would not have any impact on the Earth because the friction with the atmosphere would burn them up before they could pass through the atmosphere. A meteor with a diameter between 50 meters and 1 kilometer, however, could cause a regional disaster. A meteor with the diameter of more than 2 kilometers would change the global climate instantly, and make the Earth’s environment similar to the time when dinosaurs became extinct. Scientists have estimated that there are approximately 1,000 large near-earth comets with a diameter of more than 1 kilometer and over a million near-earth comets with a diameter over 50 meters. Therefore, we can definitely anticipate visits from “aliens from outer space.” The question is when? Among the 1,000 large near-earth comets, scientists have only been able to locate half of them so far. Because of this scientists have not been able to make a realistic prediction about comet collisions.

The ancient Chinese often associated meteors with the fate of a person or a change of a society’s future. There is a Chinese saying; “In nature there are unexpected storms while in life there is unpredictable fortune and misfortune.” Even with today’s highly advanced technology, mankind continues to pay a heavy price when it goes against the course of nature. What kind of cosmic changes will the Leonid meteor storm that took place this past November presage?

Reference:
http://www.bjp.org.cn/

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