Halley's Comet One Piece at a Time, and the Draconids (Maybe)

October's moon drops below the horizon in the middle of the night around the 20th of the month, thus affording us a good look at peak activity of the Orionid meteor shower during the predawn hours.

The Orionids, like the eta Aquarids of May, are derived from the world's most famous comet, Halley's Comet (or does that distinction now belong to Hale-Bopp?). The meteors are fast, streaking through the atmosphere at a velocity of 66km/sec. Sometimes they are bright, and about 50% of them display persistent trains. There can be a number of submaxima ("mini-peaks") during the shower, particularly around the 17-18th, when peak-like activity has been noted occasionally. This most recently occurred in 1993 and 1998.

Analysis of observational data from 1984 through 2001 by the International Meteor Organization (IMO) has revealed a roughly 12-year cycle to the strength of the Orionids' and eta Aquarids' peak. In other words, the showers' peaks are at their highest every 12 years. This suggests the influence of Jupiter, minding its own business in its own 12-year orbit.

Also, recent analysis of video data has shown that the Orionids have a single, run-of-the-mill radiant, contrary to the opinion of many visual observers, who believed the shower to have a larger, more complex radiant.

The Orionids are active from early October through early November.

You can warm up for the Orionids early in the month with the usually non-existent Draconid meteor shower.

Historically, this shower has only been active during those years when its parent comet, comet 21P/Giacobini-Zinner, is at perihelion, when said perihelion occurs during or near October. In between it is a minor, or non-existent meteor shower. But during those years when it is active ... well ... duck! This is because the meteor stream is still relatively young, and the meteoric particles are still bunched up near the comet itself.

In 1933 a storm of up to 6,000 meteors per hour, mostly faint, was seen all across Europe. In 1946, despite a full moon, more than 10,000 meteors per hour were counted in the southwestern U.S. And in 1952, with the peak falling during the daylight, Jodrell Bank radio observatory in England recorded about 200 meteors per hour by radar.

More recently, a brief outburst of about 700 Draconids an hour was observed in the Far East in 1998. The following year a surprising outburst of about 20 meteors per hour was noted, again in the Far East.

Based upon these recent observations, and equations scribbled on bits

Go To Page: 1 2

Articles in this Topic    Discussions in this Topic