We’re in for another meteor treat this time of year: the famous Leonid Meteor shower peaks before sunrise on November 17th. These showers are caused by Earth passing through a trail of dust emitted by Comet Tempel-Tuttle more than four centuries ago.
Comet Tempel-Tuttle’s Dusty Trail
The meteors are produced by particles that are shed from the Comet Tempel-Tuttle every time it passes close to the Sun during its approximately 33-year orbital journey. Trailing behind the comet is a dirty trail of very small dust particles, generally less than 1 millimeter in size. As the particles run into the Earth’s atmosphere they vaporize within a few seconds at altitudes of about 60 miles above our heads.
The showers peak between roughly midnight and 5:30 a.m. local time on November 17th as the Earth makes a 400,000-mile journey through the cloud of particles that was ejected from the nucleus of Comet Tempel-Tuttle back in the year 1567.
Larger particles, up to pebble-size, can produce brilliant meteors known as fireballs, rivaling in luminosity the brightest stars and planets and on rare occasions, even the Moon. Leonids travel at very high speeds through our atmosphere–up to 162,000 miles per hour–and some can leave bright trails of ionized atoms producing trains that can last for many seconds, or even minutes.
The mornings before and after peak may also produce some visible meteors as well.
Where Do These Meteors Come From?
The Leonid radiant (the perspective point from which all the meteors would appear to originate) is within the so-called Sickle of Leo; a backward question-mark pattern of stars that outlines the head and mane of the constellation Leo, the Lion (the brightest star in the constellation, Regulus, makes up the dot of the question mark). Hence the meteors are known as Leonids. Observers all across North America may experience a good Leonid show with meteors flashing out every few minutes. The Leonids produce an average of 20 to 30 meteors per hour, but it can vary from year to year.
Leonid Observing Tips
In order to see meteors, the sky must be clear and your selected observing site should preferentially be free of light pollution; the less light, the more meteors will be seen! Notice that Leonid meteors occur in the after-midnight hours. Hence, there is no point in starting your observation much earlier. Be very aware that it can be very cold in mid-November, so be sure to wear several layers of warm clothing.
For comfortable observing, use a reclining chair and place yourself either in a suitable sleeping bag or under several blankets. While observing, do not fix a particular star, but scan the area of sky from the northwest to east. Look patiently across a wide area of sky and wait for a shooting star to appear.
What’s In Store for 2021?
For a few days around mid-month, the sharply defined Leonid shower flares up. According to the 2021 Observer’s Handbook of the Royal Astronomical Society of Canada, the Leonids are forecast to peak before sunrise on November 17th. But unfortunately, like the Orionids, the Moon will be a spoiler, reaching its full phase just two nights after the shower peak.
The Leonids Through History
Old chronicles contain references to past Leonid meteor storms back to the 10th century A.D. The best-known Leonid meteor storms are those of 1833 and 1966 when literally tens of thousands of meteors darted across the skies during the peak hour! The 1833 meteor storm was so spectacular that it in fact launched meteor research as a branch of astronomy.
This is the famous shower that produces spectacular outbursts about every 33 years, as in 1833 when “stars fell on Alabama;” 1966 when several thousand meteors per minute left observers awestruck, and in 1999 and 2001 when 1,500 to 3,000 per hour fell. The recent lean years have generated only about a dozen Leonids per hour, but rates are expected to pick up around 2034, when rates may rise into the hundreds—or perhaps even thousands—or more per hour!
1966: Remembering The Great Leonid Meteor Shower
Over fifty years ago, beginning at around 5 a.m. Eastern Time, dawn was breaking along the Eastern Seaboard. Where clear skies prevailed, viewers were able to see “shooting stars” from the Leonids falling at rates of up to six per minute before it finally became too bright to see the stars. Farther west, where it was still dark, Leonids were falling at a rate described by many as “too numerous to count.” One observer, stationed north of Mission, Texas, said that meteors falling in all directions gave the impression of a “gigantic umbrella,” appearing to “waterfall” out of the head of Leo.
From 6,850-foot Kitt Peak in southern Arizona, thirteen amateur astronomers were trying to guess how many could be seen by a sweep of their heads in one second. The consensus of the group was that the peak occurred at 4:54 a.m. Mountain Time, when the staggering rate of 40 per second (144,000 per hour) was reached!
Blame Comet Tempel-Tuttle
Today, we know that a thick trail of dusty debris shed by Comet Tempel-Tuttle was what caused the Great 1966 Leonid Storm. That material had made two revolutions around the Sun before colliding head-on with the Earth on that memorable night over 50 years ago. Because such a trail of cosmic flotsam and jetsam is invisible until it enters our atmosphere, astronomers back then were, in essence, playing a game of blind man’s bluff, not knowing exactly if or when we might encounter it.
Now, with computer technology, it’s a much different situation—astronomers can readily locate the position of Leonid dust trails from the distant past or far into the future. Indeed, the Leonids will periodically shower our planet in the years to come; in the year 2034, Earth is forecast to move through several clouds of dusty debris shed by comet Tempel-Tuttle from the years 1699, 1767, 1866, and 1932. If we’re lucky, we might see Leonids fall at the rate of hundreds per hour, perhaps briefly reaching “storm” rates of 1,000 per hour, experts have estimated.
Enjoy the show, and here’s hoping for clear skies!