This week brings us the return of the famous Leonid meteor shower, a meteor shower that two decades ago generated much anticipation and excitement among skywatchers around the world.
Solely from the point of view of the observing circumstances, this will be a favorable year to look for these meteors, because the moon will be a waning crescent phase and should not interfere too much with meteor watchers who will be looking for these superfast, soaring meteors of the Sickle of the Lion (from which the meteors take their name).
Keep this in mind: At this time of year, meteor viewing can be a long and cold task. Expect the ambient air temperature to be well below what your local radio or television predicts.
Related: Leonid meteor shower 2022: when, where and how to see it
Leonid Meteors: Debris from Comet Tempel-Tuttle
Leonid meteors are debris thrown into space by Comet Tempel-Tuttle, which swings through the inner solar system at 33.25-year intervals. With each visit, the comet leaves behind a trail of dust in its wake. Many old dusty trails from the comet litter the mid-November portion of Earth’s orbit, and Earth slips through this debris patch every year. Occasionally we will pass directly through an unusually concentrated dust trail, or filament, which can trigger a meteor storm resulting in thousands of meteors per hour. This happened in 1999, 2001 and 2002. Since Tempel-Tuttle passed the Sun in 1998, the Leonids have given their best show in the years immediately following its passage.
Since then, the comet – and its dense dust trails – have all drifted far beyond Earth’s orbit and back into the outer regions of the solar system. Tempel-Tuttle reached the end of its elliptical path near the orbit of Uranus in 2014. As a result, Leonid activity has been rather sparse in recent years. The comet has since turned around and is now slowly approaching the inner solar system, although it is still very far away. It is expected to be closest to the sun again in 2031.
So it would seem the odds are that this year there is little to no chance of unusual meteor activity. Tempel-Tuttle dust sparkles the sky for a few nights each year in mid-November and this year the traditional peak is expected on November 18. But realistically – at best – we wouldn’t expect to see more than 5 or 10 Leonids during an hour on watch.
Still, if two well-known meteor scientists are right, this year will be an atypical one. These scientists have produced various models of the Leonid current and all indicate that Earth will cross some “rivers of rubble” left by Comet Tempel-Tuttle.
An uncertain forecast
In the 2022 Royal Astronomical Society of Canada Observer’s Handbook, meteorite experts Margaret Campbell-Brown and Peter Brown indicate that this year’s peak activity is expected to occur at 7 p.m. EST ( 0000 GMT on November 18) on the evening of November 17. This is when Earth will pass closest to the orbit of the long-gone comet, and when our planet is apparently most likely to encounter residual material from the comet. This period is very favorable for those in Central and Western Europe and Western Asia. But on the other hand, for North American observers, Leo will always be under the horizon; they will have to wait until after midnight to see the Leonids.
The main show is expected on Saturday morning (November 19). Model calculations by Russian meteor expert Mikhail Maslov and his Japanese counterpart Mikiya Sato show an approaching dust trail left by Tempel-Tuttle in 1733, interacting with Earth on that date. Maslov gives 06:00 UT, Sato predicts 6:25 UT. This translates to 1:00 a.m. to 1:25 a.m. EST (06:00 GMT to 06:25 GMT), an excellent time for eastern North America, where Lion’s Sickle will be located about one-third into the eastern sky and the moon will be just below the horizon. Earth will cross Stream 1733 at a distance of 89,000 miles (143,000 km) from the center. Maslov adds that “a lot of meteors should be bright, an hourly rate of 250-300 seems possible despite the uncertainties”. Sato, however, is much more conservative: “Hourly rates can reach 50+ as the model suggests dust tends to be less concentrated.”
Farther west, for those in the central time zone, the peak is between 12:00 a.m. and 12:25 a.m. CST (6:25 p.m. GMT), and the sickle will be noticeably lower in the eastern sky. In western North America, the only hope of catching a glimpse of anything unusual may come from an “Earth Grazer” – a meteor that scours the upper atmosphere horizontally from a radiant near from the horizon. Spectacular earth grazers are usually slow and bright, criss-crossing far into the sky and always worth seeking out. Otherwise, little or nothing of this heightened activity will be visible because, unfortunately, Lion’s sickle will either be sitting on the horizon or will not have risen yet.
There is a possible final push from Leonid on November 21 at 3:00 p.m. UT, from debris thrown up by the comet in 1800. The timing favors Hawaii and East Asia.
How to watch the Leonids
Watching a meteor shower is all about lying down, staring up at the sky, and waiting.
When you are sitting quite still, close to the rapidly cooling floor, you can feel very cold. You wait and wait for the meteors to appear. When they don’t appear right away, and if you’re cold and uncomfortable, you won’t be looking for meteors for long! Therefore, make sure you are warm and comfortable. A comfortable reclining lawn chair, thick blankets, sleeping bags, pillows and cushions are essential equipment.
Hot tea, coffee or cocoa can calm the cold while providing a mild stimulant. It’s even better if you can observe with a companion (“shower” with a friend). This way you can keep yourself awake and cover more sky.
Because the Leonids move along their orbit around the sun in a direction opposite to that of the Earth, they slam into our atmosphere almost head-on, resulting in the fastest possible meteor velocities: 45 miles (72 km) per second. Such speeds tend to produce bright, colorful meteors with hues of white, blue, aquamarine, and even green, which leave long-lasting trails or trains in their wake.
Thus, for North American observers, the emphasis might be on quality rather than quantity; for it would not be surprising if the figures quoted above by Maslov and Sato were far from exact. But a few of these meteors, although only visible for a fraction of a second, could leave in their wake bright trails of ionized atoms that hang in the sky for many seconds or even minutes, while these tiny dust particles pass through our atmosphere. at altitudes of 80 to 100 miles (130 to 160 km).
And seeing even a single meteor as bright as that can make a chilly early morning vigil worthwhile!
Joe Rao is an instructor and guest speaker at New York’s Hayden Planetarium (opens in a new tab). He writes on astronomy for natural history review (opens in a new tab)the Farmers Almanac (opens in a new tab) and other publications. Follow us on twitter @Spacedotcom (opens in a new tab) and on Facebook (opens in a new tab).
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