The Annual Leonid Meteor Shower

   During the early winter months of A.D. 902, Chinese astronomers recorded what were probably the first written accounts of a meteor shower. This event was described as a time when the stars fell like rain.Click on graphic to see it full size. Centuries later, in November 1799, the stars again fell like rain during a spectacular display witnessed across the colonies by North American astronomers. The shower activity was also recorded by the famous German scientist and geographer Alexander von Humboldt while he was on an expedition in Venezuela. During one intense period, witnesses described seeing as many shooting stars as actual stars. Approximately 33 years later (November 12-13, 1833), the skies over eastern North America were streaked with so many meteors that during a nine-hour period, observers calculated the Zenith Hourly Rate (ZHR) to be a few thousand, totalling to about 240,000 meteors.

   Following the 1833 meteor storm, interest in and study of meteors increased tremendously. By studying records, astronomers noted that meteors originate from a specific area of the sky within a certain constellation; hence the Leonids, Perseids, and so on. Observers also noted that as the night wore on and Leo “moved” westward, the shower’s point of origin stayed with the constellation. Thirty years later, after much study, Yale astronomer Hubert Newton pieced together a history of the Leonid meteor storms.

   The Leonid meteor storms (periods during a meteor shower of intense meteor activity) have been recorded approximately every 33 years dating as far back as the A.D. 902 shower observed by Chinese astronomers. Hubert Newton and other renowned astronomers predicted that another meteor storm would occur during November of 1866 or 1867, 33 years after the recorded meteor activity in 1833. Coincidentally, in 1865-66, two astronomers working independently, Ernest Tempel and Horace Tuttle, discovered a faint comet, the source of Leonid activity, which was named Comet 1866I (now referred to as Comet 55P{Tempel-Tuttle). Comet Tempel-Tuttle’s orbital period around the Sun was determined to be about the same as that of the Leonids, 33 years.

leonid-meteor-storm   The Leonid shower’s spectacular peak nights during November of 1866 and 1867 validated the two astronomers’ prediction. (Different portions of the Earth may encounter Comet Tempel-Tuttle’s meteor trail in two consecutive years because of the Earth’s changing position.) In 1866, sky observers in Europe noted that the shower’s intensity reached an average of 5,000 meteors per hour; in 1867, observers in North America counted an average of 1,000 meteors per hour. Because Tempel and Tuttle had so accurately predicted the source of the 1866/1867 Leonid meteor storm, the storm of 1899 was much anticipated and promoted by the astronomical community. Unfortunately, the Leonids did not display spectacularly that year. As a result, public interest in the storm waned tremendously. Ironically, the following year, 1900, brought storm displays with peak ZHRs of 1,000. During November 1901, the Leonids averaged about 2,000 meteors per hour.

   The Leonids’ return in the 1930s was also disappointing. Astronomers were concerned because the source comet had not been sighted since its 1866 passage. This suggested that perhaps the comet had broken apart and that the comet debris cloud would no longer be refreshed providing the source for the meteors. However, peak night averages during the 1930s were still impressive with hourly averages in the hundreds.

comet-temple-tuttle   During the early 1960s, the Leonid meteor showers started showing an increase in the hourly rate, similar to the intensity of the showers during the 1800s. In 1965 Comet Tempel-Tuttle was rediscovered. That year the shower’s intensity climbed to over 100 meteors per hour. One year later on November 17, 1966, the most intense meteor storm recorded in history occurred over the Midwestern United States-its average intensity was several thousand per hour, and at one point the storm rates were estimated at more than 100,000 meteors during a 20-minute period.

Click on graphic to see it full size.

Click on graphic to see it full size.

   So here it is 2014, and we are about mid-way through the 33-year period for the Meteor Storm. So no storm this year or for the next several years. Expect to see a few meteors streaking outward from the radiant within the backward questions mark shaped asterism of Leo, but with an average hourly rate (ZHR) of 10-20 there are often long stretches of time between sightings. And remember that all meteor showers have a span of time before and after the peak when meteors will be visible. This year the activity for the Leonids is for about one week from November 14-21 this year.

Click on graphic to see it full size.

Click on graphic to see it full size.

   This year’s meteor shower peak is calculated for 22-23 UT (4-5 pm CST) on 17 November, and will last for about eight hours, with areas of best visibility across much of North America. The radiant is near the star Regulus and the planet Jupiter. Best viewing for a meteor shower is during the hours before sunrise as the part of the Earth you are on is turning into the direction that the Earth is moving as it revolves around the Sun. In effect you are moving ‘head first’ into the cloud of cometary debris. In the Midwest United States where I live Leo rises at around 3am CST so the timing for viewing the Leonids around 94o west longitude is pretty good. And this with a thin waning crescent Moon rising after Leo rises.

nov17fluxinator   Use this NASA web site to calculate the Meteor Shower peak for your location. (Uses Java)
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

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