Star date: 11:08:98
The Leonid Meteor Shower Extravaganza
Last week, when we loked at the Sun I had stated that we would be looking at other aspects of solar observing this week. Instead, we will be treated in just a few short days to the greatest meteor shower in 33 years. Thus, we will instead look at these quick streaking visitors from space.
The Leonid meteor shower comes to visit the Earth each November, lasting between roughly the 14th and 19th of the month each year. Normally the Leonids are a slow shower, where there are only about six shooting stars per hour, or about one every 10 minutes. This normally makes the Leonids the least spectacular meteor shower of the year. Once every 33 years, however, the Earth is treated to a spectacular showing of these meteors.
To understand why this happens, first we need to understand a little bit about meteor showers themselves. Meteors are fine particles of rock, metal, and/or dust which burn up as they pass through the atmosphere of the Earth. There is quite a lot of dust and small pebbles floating through space, and so meteors can be seen periodicallly throughout any clear night. Comets, as they pass through space, leave behind tiny pieces of dust, rock and ice behind them as they slowly burn from the heat of the Sun.
Then, as the Earth revolves around the Sun, our planet encounters these trails of ice and rock, and many of the particles enter the atmosphere of the Earth and burn from the friction, producing meteors. This is what causes meteor showers.
Now, you can imagine from that idea that when the Earth encounters a trail of comet material for the first time after a passage from that comet, the meteor shower which is associated with that comet can be spectacular. This is exactly what is happening this month.
The comet which causes the Leonid meteor shower is the little known comet 1866 I Temp. This comet revolves around the Sun once every 33 years. It has just passed by the orbit of the Earth, and this should produce quite an impressive shower. The last time this happened, in 1966, there were perhaps 100,000 meteors per hour seen. This is roughly three meteors per second. During one showing in the 19th century, there were perhaps 400,000 meteors visible each hour. One Boston bound observer, even under the growing artfical light from the city (ok, it was mostly gaslight, but still...) described the shower as having "...as many shooting stars as there are flakes in a medium snowstorm ". Plus, keep in mind when he spoke of snowstorms that he was from Boston. He continued that "...many of these were as bright as full Moons."
Sadly, this year will not offer observers in the United States as much cause for celebration, however. But we are still in for a special treat. Observers in Asia, where the shower will be the best, can expect a shower of several hundred to a few thousand meteors per hour. People in the United States will be treated to at least a few hundred per hour. This means you should be able to see a meteor once every 10 seconds or so, at it's peek. Quite impressive. The drawback is that the peak is just before dawn on the morning of the 17th. In fact, this is a good rule of thumb.
The peak of any meteor shower anywhere in the world is nearly always right before dawn. Why is that? It is because the Earth rotates about it's own axis counter clockwise as seen from above the north pole. At the same time, it is revolving around the Sun counterclockwise as seen from the same perspective. The meteor shower occurs as the Earth collides with the cometary debris trail, and an observer anywhere on Earth sees it best they are most directly in line with the center of the shower, and it is due south. That is just before dawn. At 10pm on the night of the 16th, about three meteors per minute should be visible to the northeast, centered around the constellation Leo.
Clear skies, and good viewing.
