This most famously erratic of the annual meteor showers comes around again on November 17. The peak is predicted to be 23h by Universal Time – nearly midnight for Europe and thus pretty favorable. That time is from 5 to 8 hours earlier in North American clocks and not so favorable. In any case a good time to start watching is midnight between Nov. 16 and 17, Saturday and Sunday.
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This stream pf particles, derived from periodic Comet 55P Tempel-Tuttle, hits Earth almost head on. Consequently the meteors are very swift as they plunge into our atmosphere and burn up. And, since they are meeting Earth’s front side, they are mostly seen after midnight.
Their radiant – the point or small area in the head of Leo from which they derive their name and from which they appear to fly out to any oart of the sky – rises into view only shortly before midnight. It climbs, parallel with the celestial equator, as the night goes on, and is highest toward the end of the night. So, if the show proves exciting, it’s worth waiting up. By an hour before sunrise, the radiant will be almost at the zenith.
But will it be exciting? The ZHR or “zenithal hourly rate,” the number one alert person might count in an hour at the peak time and in perfect sky conditions with the radiant overhead, is given as 15. But conditions are almost never perfect and the estimate is frankly uncertain. In many years a Leonid night is moderate or disappointing. – But swarms in thus meteor stream have produced by far the most sensational, terrifying meteor “storms” in history: . in 1833 people thought heaven was falling and the world was ending, and on 1966 November 17 the estimated rate was 144,000 per hour – more than 40 a second! It would be a pity to sleep through a chance something like that.
Besides the temper the Lion happens to be in, the other important factor is the Moon. It, too, is in front of Earth, since on Nov. 19 it will reach its Last Quarter position, near what we’ve marked as “Earth’s direction of travel.” Though much less bright than it was at Full phase on Nov. 12, it could drown out some of the fainter meteors.
In this space picture, Earth is seen from ecliptic north (the north pole of its orbit). The broad flat arrow shows its flight along its orbit in one minute, and the arrow on its equator shows its rotation in 3 hours. The actual stream of particles in space is millions of miles wide; the dotted line represents only those that happen to arrive from exactly overhead. America is coming around into fuller view of the hemisphere of sky that the Leonids may appear in.
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Can anyone tell me which part of the globe, that is, which country or countries, the Leonids of 16/17 November 2019 was/were most directly in line with the shower? In the map overhead the arrow appears to point at a specific part of the world for a specific time and date, that is, 17th November, 2019, at 3.00 UT. I am conducting research on specific world events occurring within the countries most directly in line with the showers. Thank you.
My globe diagram was for the time I chose so as to show the prospect for America, not for the peak time. It really takes a meteor expert (which I am not) to say what the most probable peak time is for a shower in a given year. I decided to use my calculation based on the longitude of the sun for the date, which I found given as 235.27, and that gave Nov. 17 23 Universal Time. Another time given was Nov. 17 16 UT. The position of the radiant at the peak time is given as declination 22 north, right ascension 152 (10h 7.8m expressed in degrees). So it would be overhead at latitude 22 north, longitude based on whichever of those times you use – If 16h, it would be in the eastern Pacific, if 23h, in Chinam both about sunrise. I think. A meteor expert such as Alastair McBeath would give a more trustworthy answer.
I experienced the storm of 1966 in Indiana. Because a good show was predicted I put a chaise lounge in my driveway, carried some blankets with me and started watching an hour or two after darkness fell. As the flashes became more numerous–maybe two or thee per minute, I awakened my five-year-old son so he might have a memory of it. We huddled together and I asked him to start counting. By the time he got to ten he said: “I can’t count that fast. There are too many.” He eventually fell asleep in my arms so I took him back to bed. When I retuned I watched the shower become a storm. At one point I could actually sense the earth moving through space. Dozens of meteors at a time. I fantasized a mouse on the floor of my work shed watching me sharpen an ax. The storm wasn’t quite that strong, but for about fifteen minutes it was an apt comparison. One of my most memorable evenings. (My son doesn’t remember, alas.)
John M. Flanigan
Kaneohe, Hawaii
For many years you wrote a tease for the 1999 Leonid meteor storm. “There may be another great storm on 1999 Nov. 18, the year after the comet’s next return.”
I looked forward to it for several years and the show did not disappoint. I estimated at least 5,000 per hour.