Leonid Predictions for 2001 - BIG meteor shower

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[VRWC_Member428]

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Leonid Predictions
for 2001

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New mathematical models were introduced during 1999 which successfully predicted the date and times the Leonid meteor stream would reach maximum hourly rates in 1999 and 2000. Unfortunately, these same models failed to adequately model the intensity of the displays in 1999 and 2000. Now, after the analysis of the 1999 and 2000 displays, astronomers believe they have a better understanding of the shape and particle distribution within the various streams of debris left behind by comet Tempel-Tuttle--the parent comet of the Leonids. Most of this page contains a history of the predictions of Leonid activity; however, if you are not interested in reading the details, a brief summary of what to expect follows:
	--November 18, between 10:00 and 10:30 UT: This favors North America, especially the western half. Predicted rates range from 1000 to 4000 per hour.
	--November 18, around 18:00 UT: This favors Australia and eastern Asia. Predicted rates range from 8000 to 15000 per hour.
Lastly, I would like to point out that the moon will not be a factor this year. It is only 3-days old and sets long before the Leonids begin.

Brief History of Leonid Predictions

      Since the 19th-century discovery that the Leonids were a recurrent meteor shower capable of producing storms of meteors, astronomers have not been particularly successful at predicting the strong displays. After tremendous displays in 1833 and 1866, predictions for 1899 and 1933 failed to pan out. Another prediction for 1966 indicated a display was "possible", but nothing prepared observers in the western United States for one of the greatest meteor displays in history.
      Beginning in the 1980s investigations of the orbit of the Leonid parent comet revealed the effects of Jupiter's gravity. Suddenly, some of the failures of the past were revealed. The reason for the lack of strong displays in 1899 and 1933 were possibly due to the fact that Jupiter had tugged on the comet following the 1865 return. The result was a slightly different orbit which did not enable Earth to pass close to the comet's orbit and the comet's meteor streams in 1899 and 1933. In addition, changes in the orbit as it approached the sun for the 1965 return caused Earth to once again pass close to the stream orbit, thus apparently explaining the intense Leonid display of 1966.
      Since the 1980s, everal astronomers published predictions for the Leonid returns of the late 1990s, with 1998 and 1999 believed to be the optimum years. Donald K. Yeomans (Jet Propulsion Laboratory), a person who has extensively studied the orbital motion of the Leonid parent comet, predicted maximum would occur on November 17, 1998, at 19:43 UT, with hourly rates of 200 to 5000. Peter Brown, a leading researcher into the mechanics of meteor streams, generally agreed with the time, but gave a more optimistic estimate of hourly rates between 1000 and 9000. But the display of 1998 surprised everyone. Instead of a possible meteor storm, observers were treated to a display of about 250 per hour. To make matters worse, the display peaked about 16 hours earlier than predicted.
      For all practical purposes two failures occurred in 1998: neither the time or the hourly rate were accurately predicted. Why did these failures occur? The model of how meteors were ejected by their parent comets and how their orbits evolved were not fully understood. Through hindsight it is now realized that the primary fault in the 1998 predictions was the long-held assumption that meteor activity would increase as the distances between the Earth and meteor stream decreased AND the distances between the Earth and parent comet decreased. Thus, the strongest meteor displays would seem likely to occur the year of or the year following the parent comet's closest approach to the sun, with the actual strength of the display depending on how many days had passed since the comet had passed the point where Earth crossed the stream orbit. The time of the display's peak was assumed to be the moment Earth passed closest to the comet's orbit.
      With 1000 years of Leonid observations to draw from, why were the principles of their formation and activity levels not fully understood? The answer primarily lies in the poor quality of the available observations. The mechanism for meteor showers, which were comets, was only recognized a few years prior to the 1866 display. In addition, astronomers had uncovered enough of the historic Leonid displays to recognize the roughly 33-year period of that stream. Therefore, the 1866 display was the first to be predicted and looked for by astronomers in a large area of the northern hemisphere. Predicted storms in 1899 and 1933 never appeared, so large-scale observing programs came away with nothing. So, with all of this in mind, it comes down to the years either side of 1966, and the years leading up to and including 1998 to bring about an understanding of how Leonid meteors are distributed in the orbit of their parent comet.

Predictions for 1999

      The interesting quirk of the 1998 display inspired several astronomers to approach the analysis of the Leonid stream in a different way. Leading the pack was David J. Asher (Armagh Observatory, United Kingdom) and Robert H. McNaught (Australia). Asher constructed a model of the Leonid stream which contained a number of filaments or trails. These trails were formed as follows:

1. When the comet passes through the inner solar system every 33 years, the sun heats it up causing gas and dust to be released.
2. As the dust is ejected by the comet, it is moving at a slightly different speed than the comet and usually begins to fall behind it.
3. Jupiter's great gravitational pull slightly tugs on the comet and the ejected material, so that the comet and material are now moving in two slightly different orbits.
4. At the comet's next return the new dust released by the sun's heat is moving in an orbit different from that of the dust released at the last return.
5. When Earth passes closest to the comet's orbit during the years following its return, it encounters a number of dust trails from the comet's previous returns. The newer the dust trail and the closer we are to it, the stronger the meteor display will be.

      Asher and McNaught began comparing the model with previous appearances of the Leonids. Using computers to determine the evolution of each trail, they noted that the model predicted the time of maximum of each display with an accuracy of 10 minutes or better. Perhaps the biggest boost for their model came when it predicted a strong outburst for 1869 that should have been visible over western Asia, the Middle East, and eastern Europe. A request to astronomical researcher, Gary Kronk, revealed an account of Leonid observations made on the island of Mauritius in the Indian Ocean in that year. The indicated peak differed from the predicted value of Asher and McNaught by only 5 minutes! The paper discussing their technique was published in the August 21, 1999 issue of the Monthly Notices of the Royal Astronomical Society and included a prediction that a significant display of Leonids would occur at 2:08 UT on November 18, 1999. The predicted hourly rate was 500.
      The paper of Asher and McNaught captured the attention of other researchers. Most notable was meteorologist Joe Rao, a frequent contributor to Sky and Telescope. He made two predictions for the 1999 display: one at 2:08 UT, using the Asher and McNaught model, and the other at 4:17 UT derived by extrapolating the instances of the Leonid maximum in 1996, 1997, and 1998 up to 1999. Interestingly, Rao believed the hourly rates for 2:08 UT would be between 2,000 and 6,000 per hour.
      Another set of predictions came from Esko Lyytinen and were published in the September 15, 1999 issue of a somewhat obscure journal called Meta Research Bulletin. Although Lyytinen's paper essentially still made predictions as to when Earth would encounter the various meteor trails layed down by the comet, he used Thomas Van Flandern's satellite model of comets theory as an additional means to determine the ejection of the dust. The "satellite model of comets" theory basically replaces the widely accepted "dirty snowball" theory of comet makeup with the more controversial idea that comets are continually orbited by lots of rock and icy debris. Lyytinen was unware of the work of Asher and McNaught when he published this paper. Although the paper was basically missed by many Leonid researchers as the 1999 Leonid display approached, Lyytinen predicted there would be three peaks to the 1999 display: 500 meteors per hour at 1:40 UT on November 18, 5500 meteors per hour at 2:10 UT on the 18th, and 160 per hour at 20:00 UT on the 18th.
      According to the analysis of the International Meteor Organization, three definite maxima were apparent in the observed activity profile of the 1999 display: 1:43 UT, 2:02 UT, and 16 UT. The primary peak at 2:02 UT produced a zenithal hourly rate of about 3700. Although the Asher-McNaught model wins the battle for the best prediction of the time of maximum, the Lyytinen model was closest to the actual hourly rate. In addition, although Rao did not create a model, his studies of the historical rates of the Leonids did lead to a rate prediction that was much closer to the real rate than the prediction of Asher and McNaught. As for the other peaks, Lyytinen did predict a peak at 1:40 UT and this missed another observed peak by only 3 minutes. Lyytinen predicted this peak would produce 500 meteors per hour. Although the rates at the 1:43 UT peak were about 1200 meteors per hour, it should be noted that activity leading to the 2:02 UT peak was already in progress, so that two different Leonid streams were active at 1:43 UT. If the curve from the 2:02 display is extrapolated through 1:43 UT, it appears its rates were then 900 per hour. This means the Leonid stream encountered at 1:43 UT was producing an additional 300 meteors per hour, which is quite close to Lyytinen's prediction. Lyytinen's prediction for a meteor trail encounter at 20:00 UT did not seem to happen at first, but various analyses over the last couple of years indicate it occurred at 16 UT. This was the first indication that the predictions experienced large errors when the distance between Earth and the meteor trail remained large. Rao's 4:17 UT prediction not have occur.

Predictions for 2000

      The successes of the predictions in 1999 caused astronomers to highly anticipate the 2000 display. Predictions had already been published in the 1999 papers of Asher and McNaught, and Lyytinen. The Asher-McNaught predictions indicated one peak on November 17 (7:53 UT) and two peaks on the 18th (3:44 and 7:51 UT). They said the hourly rates would not be as high as in 1999, noting there was not enough information on the first peak to hazard a guess, but that rates of 100 per hour were possible during the two peaks on the 18th. Interestingly, Rao determined that rates of 250-500 per hour were possible on the 17th, while the peak at 7:51 UT could have rates ranging from 20 to 2800 per hour. Rao referred to the last peak as the "Leonid Wild Card Night" and explained, "since the various pros and cons are virtually equal ... We could get a ZHR as low as 20-30 . . . or as high as 1400 to 2800!" Lyytinen's model once again predicted similar dates and times as the Asher-McNaught model. His times were 7:50 UT on the 17th, 3:40 UT on the 18th, and 7:50 UT on the 18th. For rates he predicted about 215 per hour on the 17th and 700 per hour on both peaks on the 18th. The predicted peak at 3:40/3:45 UT was one of some uncertainty. Both models said this peak was produced by a stream left over from the 1733 return of the Leonid parent comet. The question here was how spread out would the stream be for the 2000 display?
      Two new sets of predictions are also put forth for the 2000 Leonid display. Both papers predicted times that tended to agree with the models published in 1999, but they made an attempt to better understand how meteors were ejected by the parent comet and how they disperse within the stream. The main purpose of these papers was to better predict the strength of a Leonid display. Both predictions were developed following an in-depth analysis of the activity curve of the 1999 display.
      C. Göckel and R. Jehn published their paper in the September 1, 2000 issue of the Monthly Notices of the Royal Astronomical Society. They simulated the ejection and motion of 61,000 particles during the last four apparitions of the Leonid parent comet and determined the probable flux rates visible from Earth. One simulation revealed an activity curve virtually identical to that observed during the 1999 display. They concluded that the particle density of a dust trail is more important to its evolution than is the velocity the particles were ejected from the comet. Their model predicted peaks on November 17 (7:55 UT) and November 18 (7:55 UT and 11:30 UT). The 11:30 UT peak was a new one to look for that was not indicated by the other models. The peak at 3:40/3:45 UT was not modelled, because they did not investigate old Leonid material that would have included the 1733 stream. Göckel and Jehn indicated the November 17 display could begin showing enhanced activity around 0 hours UT and would probably not fully end until about 16 hours UT.
      The second paper was published in an issue of Earth, Moon, and Planets. The 10-author paper, featured Peter Jenniskens as the principle investigator, with the other 9 authors being members of the 1999 Leonid MAC mission. Using the 33,000 Leonid meteors detected using video cameras aboard the mission, Jenniskens notes that the resulting activity profile resembles a "Lorentz profile", which basically indicates the presence of a very sharp peak. The most important conclusion to this paper is that the existence of the Lorentz profile indicates Earth passed deeper into the Leonid dust trail in 1999 than was earlier predicted and that displays in the next few years will not be as strong. He predicted peaks on November 17 (7:53 UT) and November 18 (7:51 UT and 18:19 UT). As with the Göckel and Jehn model, he did not investigate the older material, so no prediction was made for the possible 3:40/3:45 UT peak. Jenniskens' rates were much lower than predicted by the other models. He expected a rate of just over 200 per hour on the 17th, and about 70 per hour for each peak on the 18th.
      According to the analysis of the International Meteor Organization, three definite maxima were apparent in the observed activity profile of the 2000 display: 8:07 UT on the 17th, as well as 3:24 UT and 7:12 UT on the 18th. Missing from these times are the 11:30 UT prediction of Göckel and Jehn and the 18:19 UT prediction of Jenniskens. Although at first glance it would seem the models were successful in predicting the observed times of maxima, a closer look reveals rather large errors, especially in the two peaks on the 18th. Every model was predicting the first maximum would occur between 7:50 and 7:55 UT and this ended up being 12 to 17 minutes too early. The models of Asher-McNaught and Lyytinen had predicted the second peak would occur around 3:40 to 3:44 UT, and this ended up being 16 to 20 minutes too late. All of the models predicted another maximum around 7:51 to 7:55 UT, and this ended up being 39 to 43 minutes too late. What this seems to imply is that the predictions work best for near-center encounters, but, for some reason become more uncertain as the distance from Earth to the center of the stream increases. As for the maximum rates at each peak, none of the models were consistently close, with the actual zenithal hourly rates coming out to 130 at 8:07 UT on November 17, 290 at 3:24 UT on November 18, and 480 at 7:12 UT on November 18.

Predictions for 2001

      The predictions for the 2001 return of the Leonids are an interesting group ranging from unchanged models from 1999 to revisions published just a month or so before the Leonid maximum. The one thing all of the models have in common is that they include predictions indicating at least one and probably two peaks in excess of 1000 meteors per hour.
      Asher and McNaught remain steadfast in their predictions as to the times the peaks will occur in 2001. From their landmark 1999 paper, they predict three maxima will occur on November 18, one at 10:01 UT, another at 17:31 UT, and the last at 18:19 UT. They did adjust their predictions as to the rates of the 2001 display shortly before the Leonid display of 2000. They indicate a possible rate of 2500 per hour during the first peak, 9000 per hour during the second, and 15000 per hour during the last.
      Lyytinen published a revision of his 1999 paper around the middle of 2001. With co-authors Markku Nissinen and Tom Van Flandern, they concluded that nongravitational forces were apparently an important factor in determining how the particles spread around the orbit. They showed how this factor improved the fit of his model to the activity profiles observed in 2000 and even 1999. Predictions were then supplied for 2001 and a total of three peaks were indicated, of which two partially overlap. All three peaks occur on November 18 UT, with times of 10:28, 18:03, and 18:20. His predicted rates are 2000 per hour at 10:28, 2600 per hour at 18:03, and 5000 per hour at 18:20. The activity that peaks at 18:20 UT actually begins before the activity that peaks at 18:03, so the two would combine to produce possible rates of over 7000 per hour.
      Peter Brown and B. Cooke published a prediction for the 2001 display in the September 2001 issue of the Monthly Notices of the Royal Astronomical Society. They essentially determined the times Earth would cross the various Leonid streams, just as was done in the Asher-McNaught and Lyytinen models, but their model indicates more of a dispersion of the meteors. Their prediction is that a "broad and relatively strong" maximum will occur with a peak of possibly more than 1200 meteors per hour falling between 10 and 12 UT. A much broader secondary maximum could occur around 17:30 UT with rates near 500 per hour.
      Peter Jenniskens submitted a paper to the Journal of the International Meteor Organization in mid-September that is unpublished as of this writing. Jenniskens is using all of the information he gathered during NASA's Leonid MAC mission of 1999, as well as ground observations during 2000, to produce a very complex model that ultimately predicts that the dust trails are actually shifted closer to the sun than previously believed. Jenniskens also expanded his analysis of the Leonid dust trails to cover nearly four centuries of trail evolution. Jenniskens actually predicts 7 trails will be encountered this year. Some will be relatively minor, but there could be four trails that will produce 500 to several thousand an hour. The three greatest peaks will occur at times that differ little from the predictions of the Asher-McNaught and Lyytinen models, with times of 10:09 UT, 17:08 UT, and 17:55 UT. The expected rates are 4200, 1800, and 2700 per hour, respectively. Jenniskens' analysis also reveals the last two peaks will also be joined at 17:01 UT and 17:21 UT by trail encounters producing 170 and 510 meteors per hour, respectively. This means that no less than four trails may be contributing to the activity levels being observed by people near the general longitude of eastern Asia. Jenniskens' model predicts the other two enhancements will occur at 12:07 UT and 13:57 UT, but these will only amount to 40 and 14 meteors per hour, respectively.

Conclusions

      The years 1999 and 2000 generally confirmed the mathematics behind predicting the times of strong meteor displays, while this year will help determine which model best predicts the actual hourly rates of the display. The year 2001 may be the last chance to get a clear understanding of the activity levels as Earth encounters the various Leonid dust trails. The year 2002 has the potential of producing a larger display than in 2001, but a nearly full moon will wipe out the fainter meteors and prevent a clean interpretation of the activity levels. After 2002, encounters with the newer Leonid dust trails will decline. The various models predict a break of three years may follow with "normal" Leonid rates of 10 to 15 per hour. The models then indicate another peak of over 100 per hour in 2006 and a possible similar peak in 2007. Thereafter, it appears that the 33-year cycle of intense displays will end for nearly 100 years, as Jupiter once again deflects the whole system of trails just enough to prevent the encounters with Earth. In other words, there will be no enhanced displays in the years surrounding 2033 and 2066.

[VRWC_Member428]

If you don't want to miss this, plan to stay up late, and pray there aren't any clouds!

[John H K]

Yeah, I was planning on posting some stuff on this in the week prior to the return. Actually, for East Coasters, it's getting up early, not staying up late, necessarily.

Most people hear about these showers from their local TV weathermen and they have a remarkable ability to completely botch information..during previous returns, they were even getting the dates wrong (off by a day), not emphasizing it's pretty much a complete waste of time to look for Leonids before midnight, etc.

[Ron C.]

I may be on top of one of the highest mountains near and easy to access from Los Angeles - Mt. Pinos. There will probably be over 200 telescopes up there, all privately constucted, as the locals get together for a photo-fest of the event. It ought to be fun - IF the weather cooperates.

[John H K]

The absolute LAST thing I'd want to be fiddling with during a major Leonid storm is a telescope...I realize there are people that experiment with telescopic studies of faint showers but the last thing I'd be doing during the Leonids is using a telescope.

[Ron C.]

Just an ordinary wide angle camera lense should do the job, I'd wager - and LOTS of film, or data-storage space 8^)

[VRWC_Member428]

Just an ordinary wide angle camera lense should do the job, I'd wager - and LOTS of film, or data-storage space 8^)

I have an Olympus C3030 digital camera. But it doesn't do well for long exposures because of digital noise. I purchased it about one year ago, and recently I tried the C4040 in an electronics super-store. With this baby, I can take a 16 second exposure with very little noise! Too bad I can't simply buy a new camera at this time. It owuld be neat to see 16 seconds worth of meteors. Too bad this won't happen again for 100 years.

[Ron C.]

Tx for the tip - I'm going to buy something new soon. Been looking at the high-end jobs. I want something I can swap lense with, if possible something that will accept my current large collection of. I might be wishing the impossible, and the manufactures aren't interested in meeting that need I fear.

[VRWC_Member428]

While the Olympus C 4040 is the best digital camera I've tried for long exposures, there are only three add-on lenses made for it. However, there are some digital SLR cameras which will take any lense you could put on an SLR camera. Of course, expect to pay more for these digital cameras. Also, when you buy it try taking a 16 second exposure of a very dark area. Ideally, the camera will be secured to the demo stand with a cable, and there will be a large hole where the cable goes in. Stick the lense down there and take a good long exposure. That's a great way to check for noise in the resultant picture.

I wish I had a 4040... I could make some really great looking "ghost" pictures that don't have digital noise in them.

[SunkenCiv]

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[Recovering Hermit]

It looks like your post may be about 6 years too late.

[SunkenCiv]

Sorry, my time machine settings were off. :’)

[Recovering Hermit]

LOL!

Was this a mouse-click gone awry, or is there something related to the Leonids this year and the end of civilization as we know it I should be aware of?

[Theo]

I was hoping to see something exciting about the Leonids. Hm.

I remember 2001 — aMAZing!

[SunkenCiv]

Found the topic in a search for Jenniskens.