The following are excerpts of information found on the internet, to help interested persons find the best web site about the Leonid Meteor Shower of Nov 17/18 1998, and all information is credited by the web address where it was found.
Please go to the URLs indicated for the complete text and additional information.
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The November Leonids: Will They Roar?
http://ssd.jpl.nasa.gov/leonids.html
Donald K. Yeomans
Jet Propulsion Laboratory/California Institute of Technology
Each November when the Earth runs into the dusty debris from periodic comet 55P/Tempel-Tuttle, some Leonid meteor shower activity is noted. These annual displays of meteors, or shooting stars, seem to originate in the constellation Leo so they are termed Leonid meteors. Normally, the observed rate of the Leonid meteors is about 15 per hour under ideal observing conditions. However, every 33 years or so when the parent comet Tempel-Tuttle returns to the Earth's neighborhood, there is a possibility that the Leonid meteors rates can get substantially higher. In some years such as 1799, 1833, and 1966, when the Earth passed particularly close to the tube of debris following in the comet's wake, there were Leonid meteor "storms" noted of up to 150,000 meteors per hour. Periodic comet Tempel-Tuttle passed closest to the sun (reached perihelion) most recently on Feb. 28, 1998 and a month later on March 5, the comet passed through the plane of the Earth's orbit about the sun.
Another way of saying the same thing is to note that the comet passed through the ecliptic plane from north to south or it passed through its descending node. We can expect the maximum Leonid meteor shower activity when the Earth arrives close to this nodal crossing point on November 17, 1998 at 19 hours 43 minutes Universal Time (UT). The peak Leonid meteor shower activity takes place within one hour but some activity can be observed for a few hours on either side of this peak. Unfortunately for observers located in the United States, the Nov. 1998 shower maximum will occur during daylight hours (2:43 pm local time on the east coast and 11:43 am on the west coast). While some enhanced 1998 Leonid activity may be visible just before dawn for U.S. observers, the Leonid shower maximum should be best observed by those located near the regions of Japan and eastern Asia. In November 1999, the Leonid shower will be best observed from the regions near Europe and North Africa.
Table 1. Predicted Leonid Shower Circumstances.
Although slightly enhanced meteor shower activity was evident in 1996 - 97, impressive meteor showers are most likely in 1998 and/or 1999.
Predicted time of Observed time
Leonid shower peak of shower peak ZHR Good observing
Date (UTC) HH:MM (Hours) meteors/hr Locations
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1996-Nov-17 07:20 05 - 10 60 Eastern U.S.
1997-Nov-17 13:34 12 - 14 40 Western U.S., Hawaii
1998-Nov-17 19:43 200 - 5000? Japan, Asia
1999-Nov-18 01:48 200 - 5000? Europe, North Africa
As noted in Table 1, the predictions for the times of the 1996 and 1997 maximum shower events were rather accurate and there is no obvious reason to think that the 1998 and 1999 predictions will be seriously in error. What sort of Leonid meteor rates can we expect in 1998 and 1999? Meteor shower rates are often expressed in terms of the so-called zenith hourly rate (ZHR) or the hourly rate of meteors an observer would witness under ideal conditions with the meteors appearing directly overhead (at the zenith). The geometric circumstances between the comet's orbit and that of the Earth for 1998 and 1999 are most similar to those circumstances during the Leonid showers in 1866-67 and 1931-32. Since the observed Leonid meteor rates in 1866-67 and 1931-32 were approximately 5000 and 200 per hour respectively, we might anticipate a zenith hourly rate in 1998 and 1999 bounded by the rates witnessed in the earlier events - between 200 and 5000 meteors per hour.
Like the weather, it is extremely difficult to predict the hourly rates of meteor showers. Table 1 is meant only as a rough guide. Peter Brown, a respected researcher of the Leonid meteor phenomena, has suggested a more optimistic prediction of between 1000 and 9000 meteors per hour in 1998 (zenith hourly rate). In any case, it is well worth the effort to observe the upcoming Leonid meteors since it will be another century after the 1998-1999 events before significant Leonid meteor displays are once again likely.
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International Meteor Organization (IMO)
http://www.imo.net/news/leohints.html
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Observing Hints for the 1998 Leonid Return
Rainer Arlt, Sirko Molau, Malcolm Currie
A guide to observing the 1998 Leonid activity is given. Expectations of peak time and activity profile are presented, and hints on visual, telescopic, video and photographic observations are given with the intention to derive scientifically useful data about the whole activity range of the 1998 Leonids.
1. What is expected
The return of the Leonid meteor shower is no doubt the major astronomical event of 1998. The observing network which has been established within the International Meteor Organization in the last 15 years, provides us with all means for getting a complete picture of the Leonid meteor shower. This guide covers the whole range of activity we are expecting, not just the moment of highest rates, since we should not forget about deriving accurate results for off-peak rates as well.
The Leonid meteoroid stream is linked to the periodic comet 55P/Tempel-Tuttle. The comet has an orbital period of 33.2 years and was rediscovered on March 4, 1997 [1]. For a prediction of the peak time of meteor activity, the time of nodal crossing of the comet is important. The node lies at omega=235.258°, and the Earth will pass the node at lambda=235.29° which corresponds to Nov 17, 20h UT.
Comparing the 1998/1999 Leonid return with past events, we find that the encounter conditions are similar to those of 1866. If we use the 1866 ZHR profile of [2] for a prediction in 1998, we find ZHRs above 1000 between November 17, 19h and 21h UT. The ZHR will have returned to a level of 100 at 23h UT. The background component is fairly broad and lasts for about 12h with ZHRs above 50 according to the 1996 results [3] and for about 10h according to the decay exponent of 1866 given in [2].
Figure 1 shows a sort of visibility function of the Leonids. It will be interesting to know how many hours before the peak time the radiant will be sufficiently high above the horizon. The later limit will be dawn, and the period before the Sun approaches the horizon will be interesting too. We coupled both times by multiplication, since this operation gives only one maximum where both times are equal. Best observability with a minimum radiant elevation of 40° and a minimum depression of the Sun of 12° is in the north-east of China.
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Visibility function of the Leonid peak on November 17, 20h UT. The number of hours with the radiant above 40° elevation and the number of hours with the Sun more than 12° below the horizon are multiplied. The contour lines are not radiant elevation lines; they indicate where the best combination of dark hours and high-radiant hours can be found. The area in the north-east of China has the best conditions, provided the peak-time prediction is correct.
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We may construct a scenario with a peak equivalent ZHR of 10,000 meteors per hour. Given this maximum rate, Figure 2 shows an overview of expected activity at different geographical locations. All positions refer to the same local time - 3h 30m, when the peak is expected in eastern Mongolia and north-eastern China. The activity profile was defined by the exponential-decay constants derived for 1866 in [2]. You can read the geographical longitude as a time axis: Positions east of Mongolia represent times before the peak, positions west of Mongolia represent times after the peak. The radiant elevation at that local time is included as well, giving the visible meteor rate at a limiting magnitude of 6.5. Observers in Japan will see about 1000 meteors per hour in the night November 17-18, shortly before the peak will take place. As it is dark until more than an hour later in Japan, they will observe strongly increasing activity. European observers will see a rate of 100 at best in the same night, that is, after the maximum. American observers will face a low activity of 10-20 on November 17-18. They may have seen, however, higher rates before the peak as shown in the lower part of Figure 2. Visible rates are between 20 and 50 in the night November 16-17. Hawaiian observers are closest to the peak on the western hemisphere with rates of 100. Note that the date now switches to November 17-18 when you consider Japan as above. Again, note that this graph of visible rates is only one of the scenarios possible, the predicted peak activity of 10,000 may well be wrong by a factor of 10 towards both lower or higher rates.
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Expectation of visible rates for all geographical positions. The predicted visible rate at lm=6.5 mag is given for a local time of 3h 30m local time at each position. The upper graph refers to the night November 17-18, the lower graph shows the night November 16-17 for America, Europe, and Africa.
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Although these predictions look quite accurate, we should definitely not rely on them and be prepared for the full range of activity at any location. It is indeed most unlikely that the peak will be shifted by more than 2 hours or that the background activity is much higher than anticipated. However, if something very unusual happens and we are not properly prepared, we will lose the chance of the first global, scientific monitoring of a Leonid meteor storm.
For everyone who intends to travel to central or eastern Asia, the hints for using astronomical equipment on cold climates [4] are warmly recommended. Night temperatures below -20°C (below -4°F) are very common in Asian desert and prairie areas in November.
2. Hints for visual observers
The Leonids will cover the whole range of activity from usual major-shower rates up to perhaps several meteors per second within a few hours. It will be very difficult for visual observers to cope with these conditions. We will describe the techniques for which a visual observer should be prepared, depending on the visible rate of meteors which would be recorded if continued for one hour (HR).
In this article, you'll find a modified form for the observing report. The ``Observed shower'' will be LEO, and you can fill in up to 30 observing periods in the form. One period should contain between 10 and 30 meteors. You should, therefore, not forget to give enough time marks on your recording device. If you were not able to discriminate Leonids from sporadics due to high activity, just write TOT in the blank shower field in the header of the table and leave the number of sporadics empty.
Magnitude distributions should be given with 40 to 80 meteors. Please select some of those time marks for the boundaries of magnitude distributions which were already used in the upper table for observing periods.
2.1 Major-shower activity
A tape recorder or the somewhat awkward looking paper-roll technique have proven capable of recording up to 500 meteors per hour. This rate corresponds to 8 meteors a minute. Since meteors are assumed to be randomly distributed, rates may be 15 meteors per minute occasionally. The average rate is thus misleading. Even a usual major shower like the Quadrantids, Perseids, or Geminids can keep you talking or writing continuously for a minute or two which are followed by periods of quiescence.
You should not stop your tape but just speak a magnitude into the microphone whenever you see a meteor. Note that the shower information is not very important for hourly rates beyond 200, since the error caused by the very few sporadic meteors is small. A rate of 200 meteors per hour corresponds to 3 to 4 meteors per minute.
You should not stop reporting magnitudes of the meteors even if you feel uncertain about the quality of your estimates. If all your fellow observers are doing so, meteor quantities will yet be large enough to obtain a good average population index.
The estimation of limiting magnitudes will often be interrupted by meteor sightings. It is suggested to stop the observations for limiting magnitude counts. It's hard to stop recording when many meteors are falling, but it will only be for a short interal of one or two minutes, and remember that the accuracy of the final ZHR highly depends on a reasonable estimate of the limiting magnitude. Don't forget to regularly count two limiting-magnitude fields during your observation.
2.2 Strong activity (HR=500-4000)
This range of meteor rates covers 8 to 67 meteors per minute on average. In other words: It will be between `sometimes' and `always' that you are not able to report reasonable magnitudes of the meteors anymore. An activity of 4000 meteors per hour is roughly 1 meteor per second. Again, due to the random temporal distribution of meteors, seconds with three or four meteors will occur as well as quiet seconds.
Try to record magnitudes of the meteors as long as possible. Don't worry if you start feeling less confident in your estimates - the large number of meteors recorded will give your results sufficient statistical significance. You should not stop your tape recorder after each meteor; just speak onto the running tape. Times can be derived afterwards from playing time. Nevertheless, for calibration purposes, it will be useful to record the times of start and end onto the tape. So your recordings will contain an exact start time, then (hopefully) plenty of magnitudes or bleeps, and an exact end time when the tape was stopped.
2.3 Storm level (HR>4000)
A rate of one or two meteors per second on average should be recordable by simple `beeps' which you speak onto the tape; higher rates will soon become impossible to record because of the uneven temporal distribution of meteors. You may switch to 10-meteor countings, that is, you `beep' onto your tape when you have the impression that 10 meteors have appeared. The same method of recording the time as in Section 2.2 should be applied here.
Another method was used by observers in 1966 who were completely taken by surprise when they saw many meteors a second. Observer swept their gaze across the sky for one second and estimated how many meteors they saw. A maximum value of 40 was reported. This method bears uncertainties in both the estimation of the number of meteors and the estimation of how long one second is. This year, we have the chance to check visual estimates by video technique (see below), and if we try the same visual method as in 1966, we can calibrate the old activity estimates by comparing our 1998 visual and video results. A powerful software to check your capabilities of monitoring meteors at storm conditions can be found on the internet at ftp://www.imo.net/pub/software/metsim/. Investigations on the reliability of visual observations based on that program were published in [5].
3. Hints for video and photographic observers
Whereas the observation of very high meteor activity will be most exciting for visual observers, it is the ultimate domain for video systems. A video camera is an emotionless piece of electronics that supplies accurate figures no matter if there is one meteor per hour or one per second. In fact, if a meteor storm establishes this or next year, it will be for the first time that we get reliable quantitative measurements of meteor storms at all.
3.1 Activity profiles
The main goal for video observers will be the determination of meteor activity followed by meteoroid flux computations. For this purpose, all types of video system (see [6] for a detailed discussion of the different camera types) may be used.
Similar to visual observers, wide angle cameras combine a large field of view with moderate limiting magnitudes. They are able to record a vast number of bright meteors. From the ratio of bright and fainter shooting stars we can derive the mixture of different particle sizes found in the meteoroid stream. Because of their similarity to visual observers, wide angle video systems are the first choice for the calibration of 1966 visual data as explained in Section 2.3.
Normal and tele video systems have successive smaller fields of view, but are also able to record fainter meteors. Thus, they extend the flux profile obtained with wide angle systems to smaller meteoroids causing fainter meteors. With their help we will be able to find out, whether the Leonid acitivity cuts off at a certain magnitude, or if the number of meteors is continues to increase exponentially towards those which cannot be detected by the naked eye anymore.
Finally, a battery of video systems with different lenses gives us the unique chance to study meteor activity over a range of about 15 magnitudes - from fireballs with -7 mag down to the faintest meteors of +7 mag! We suggest that video observers at the same place arrange their activities to gain a large coverage of particle sizes and a maximum of information.
At locations where no video cameras are in operation, photographic equipment can also be supportive in meteoroid flux estimates given very high Leonid activity. When you are lucky enough to experience such rates try to make five minute exposures. Away from the times of highest activity you can increase the exposure time to 10 or 20 minutes to cover the entire night with a single film.
3.2 Meteoroid orbits
Another observing goal may be the determination of Leonid orbits from the storm filament. For this purpose we suggest the use of photographic equipment. Though video systems will record orders of magnitudes more meteors, the accuracy of meteor photographs is clearly superior. This is caused by the up to 10 times higher spatial resolution of film material compared to the phosphorous screen of an image intensifier. The expected high activity will result in a sufficient number of meteor photographs, which will give the best meteoroid orbits.
3.3 Other aims
Given the large quantities of bright meteors expected, certain special studies may be carried out by means of video and photographic equipment.
High resolution meteor spectra are rare, because the chance of capturing a meteor beeing bright enough is extremely small. Using a high precision grating, the limiting magnitude of the detector is about 3 mag lower for meteor spectra than for meteors. Cheap holographic plastic grating cause another loss of 1 to 2 magnitudes. That is, in the absence of large meteor showers you will have to operate your camera on average in the order of several (video systems) to several thousand hours (photographic equipment) until you have secured a spectrum. Even during the Perseid's maximum average exposure times between several tens of minutes and hours are to be expected. As the activity during a meteor storm surpasses major meteor showers by some magnitudes, you have a fair chance of recording several high quality photographic spectra in one night. Even more, with the help of video systems it will be possible to assess differences in meteor spectra of one meteoroid stream from a large statistical sample.
Another special target for video and photographic observers may be persistent trains. The Leonids are caused by fast meteoroids of cometary origin. They are known to produce a large number of persistent trains, sometimes visible for several tens of minutes [7]. The larger the meteor number, the higher the chance to record bright persistent trains and their deformation by winds in the high atmosphere. Here video systems have the advantage to minutely track all changes. On the other hand, you can use longer exposure times with photographic equipment and thereby follow the train development even after it has become invisible to visual or video observers. If you possess a grating or prims, but no video equipment, you should definitely consider having a camera with your spectral equipment at hand when a very bright fireball appears leaving a train persisting for may tens of seconds. Meteor train spectra are extremely rare, and the Leonid maximum offers the higher the chance to record bright pe
Last but not least, both video and photographic equipment can present you an unique souvenir from a unique event. Every video observer knows about the excitement of the audience when some recordings of the Perseids are presented. A photograph of the 1966 Leonids showing more than 70 meteors has become famous not only among meteor observers, but among the whole community of astronomy enthusiasts. So, use the chance to produce your own memorable video and photograph! Who will be able to present ``stars falling like rain'' on a video screen in real time? Who will be the first having a hundred shooting stars on a single photograph? We wish you much luck with your experiments!
4. Hints for telescopic observers
In these days of video, you would be forgiven for thinking that telescopic observations of the Leonids have minor import. Video systems are still uncommon; many of those will be trained on the maximum in China or Japan, or concentrate on visual meteors. To garner a comprehensive picture of a Leonid outburst, it's imperative to observe meteors across the full spectrum of brightness (mass). Remember that telescopic meteors vastly outnumber their visual counterparts. Telescopic data provide information about the meteors fainter than visual, and is the only means open to amateurs of gathering information for meteors fainter than +9 mag.
The main goals are to determine the meteor flux of faint Leonids throughout the period of activity, not just at the maximum; and to determine the time of peak activity. If you are fortunate to have a selection of telescopes and binoculars a) choose a wider apparent field of view (up to about 70°) to maximise the number of meteors seen, and b) select the largest suitable instrument to detect the faintest Leonids.
4.1 Normal activity (HR
Plotting is feasible up to around HR=25-30 based upon experience at a dark site during the Geminid peak. Thus for rates below about 30 meteors per hour, adopt the standard plotting technique, alternating between two fields of view approximately every 30 minutes. Suitable pairs of IMO charts are 123 and 147, 80 and 146, 81 and 145, 103 and 146. Measurement of the deadtime while recording the meteor details and plotting its path is especially important so these data may also be used for flux measurements. Do not forget to record the decay time and distortion of persistent trains if the meteor frequency permits.
A report form for telescopic observations is supplied with this article.
Be prepared to switch to the following technique should rates become too high. Observers are expected to use their judgement as to what is unmanageable.
4.2 Enhanced activity (HR=30-500)
These rates are too high to plot. At a given time the smaller field of view compared with that of the visual observer will make scientific observations somewhat easier, not least because the observed rate is expected to be lower. However, the onset of higher telescopic rates may occur before the visual rate accelerates.
Select one field. This need not be an IMO chart region, though these are strongly preferred as they will enable limiting magnitude estimates within the field. The important thing is to have a wide range of star brightnesses, be situated 10-20° from and be at a higher elevation than the Leonid radiant. Proceed as if observing with the naked eye, as described in Sections 2 and 2.1. Note that this requires equipment not normally used for telescopic watches. So if you're not familiar with the paper-roll technique or using a tape recorder, practise with them prior to the Leonids so they become second nature. Note that accurate limiting magnitude estimates using several stars in the field are vital, and will need to be estimated regularly. For those using their own fields lacking a magnitude sequence within the field should estimate the naked-eye limiting magnitude. In the case use the standard counting method in two regions in the vicinity of the telescopic field.
Record the magnitude of the meteors seen, and in addition the shower association for non-Leonid meteors; all such meteors are deemed to be sporadic. This will save time if there is a short flurry of activity. It will be obvious which meteors are Leonids as they will dominate the sporadic meteors. As you will need to estimate magnitudes quickly and `on-the-fly', become familiar with the integral magnitudes of selected field stars spanning the range of brightnesses expected. Again it is best to do this before the Leonid activity commences.
4.3 Strong activity (HR=500-4000)
Again see the corresponding visual tips in Section 2.2. If the rate goes to one every few seconds to one per second, dispense with the shower discrimination, and just note magnitudes. You can also omit the ``plus'' before the magnitude; a negative magnitude meteor will be a stupendous, but rare sight. In execeptional cases you may wish to pause to allow your eye(s) to rsecond, 4.4 Storm level (HR>4000) At this point it is going to be very difficult to stay glued to the eyepiece even though you can see meteors continuously. The visual sky will be stunning. If observers can make some measurements at the eyepiece during storm activity, these data will be most valuable, but it would be understandable if you wanted to witness the spectacle of a lifetime across the whole sky. Again adopt the visual technique (Section 2.3) of beeping as meteors appear in the field. There should not be any need to sweep, however. It should be easier to estimate the telescopic count than visually because of the narrower apparent field of view.
References
[1] B. Marsden, IAU Circular No. 6579, March 1997. [2] P. Jenniskens "Meteor stream activity. II. Meteor outbursts", Astron. Astrophys. 295, 1995, pp. 206-235. [3] P. Brown, R. Arlt "Bulletin 10 of the International Leonid Watch: Final Results of the 1996 Leonid Maximum", WGN 25:5, October 1997, pp. 210-214. [4] C. Trayner "Using Astronomical Equipment in Cold Climates", WGN 25:6 , December 1997, pp. 236-247 [5] H. Lüthen, S. Molau, "Can Visual Observers Accurately Estimate Meteor Rates in Meteor Storms?", WGN 26:3, June 1998, pp. 109-117 [6] S. Molau, M. Nitschke, M. de Lignie, R.L. Hawkes, J. Rendtel, "Video Observation of Meteors: History, Current Status and Future Prospects", WGN 25:1, February 1997, pp. 15-20 [7] S. Molau, G. Volker "Spectacular Leonid Fireball", WGN 25:1, February 1997, pp. 54-56
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webmaster@imo.net; last change: July 29, 1998
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The Experts Speak: But what do they know?
Even though the experts are predicting the storm will occur over east Asia, it's still worth looking if you're located elsewhere. The experts have been wrong before, notably in 1966. In that year the Leonids were expected to occur over Europe, but observers in North America were treated to a spectacular shower thousands of miles away. This recollection by James Young at JPL's Table Mountain Observatory in California gives a sense of what the storm was like:
"This very noteworthy [1966] meteor shower was nearly missed altogether.... There were 2-5 meteors seen every second as we scrambled to set up the only two cameras we had, as no real preparations had been made for any observations or photography. The shower was expected to occur over the European continent.
The shower peaked around 4 a.m., with some 50 meteors falling per second. We all felt like we needed to put on 'hard hats'! The sky was absolutely full of meteors...a sight never imagined...and never seen since! To further understand the sheer intensity of this event, we blinked our eyes open for the same time we normally blink them closed, and saw the entire sky full of streaks... everywhere!"
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Leonids Made Easy
http://medicine.wustl.edu/~kronkg/Leonidsez.html
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What are the Leonids?
The Leonids are a meteor shower. They are called the Leonids because they appear to radiate out of the constellation Leo. A Meteor, also known as a "shooting star," is a particle from space. Its typical size ranges from that of a grain of sand to that of a pea. A meteor appears when it enters Earth's atmosphere and burns up high overhead. Meteors can be seen on any night, but Earth enters clouds of particles several times each year and the result is a meteor shower.
What Do the Leonids Look Like?
All meteors appear as brief streaks of light moving a short distance across the sky. Some meteors move slow and some move fast. Here is a video of a bright, slow meteor. Note that a streak persisted for a little while after the meteor vanished. This "streak" is called the train and is basically a trail of glowing dust left in the wake of the meteor.
The Leonids are fast meteors and they leave lots of trains. They enter Earth's atmosphere traveling at speeds of over 158,000 miles per hour (mph). For comparison an Indy race car can reach a top speed of about 250 mph, the fastest jet has a top speed of 2190 mph, and an orbiting spacecraft has an average speed of 20,000 mph. Besides being fast, the Leonids usually contain a large number of very bright meteors. The trains of these bright meteors can last from several seconds to several minutes.
Where Do the Leonids Come From?
Most if not all meteor showers are produced by comets. In the case of the Leonids the parent comet is named Tempel-Tuttle (click here for detailed info on this comet) and it makes an appearance in our skies every 33 years. Comets are composed of ice and dust. Every time a comet approaches the sun the ice melts and dust is released. Eventually the dust spreads completely around a comet's orbit, but most of the dust stays close to the comet. When Earth passes through the dense cloud of dust the result is a spectacular meteor shower or a meteor storm. Meteor storms produce several thousand meteors per hour.
When Do the Leonids Occur?
Every November 17 Earth crosses the orbit of comet Tempel-Tuttle and the Leonids become visible. An observer with clear, dark skies can see 10 or 15 Leonid meteors every hour on that morning. Unless an observer is living at a very high northern latitude (generally within the Arctic Circle), the Leonids are only visible during the morning hours. Since Tempel-Tuttle passed closest to the sun in February of 1998, the years 1998 and 1999 should produce very strong displays. Astronomers predict in 1998 that the meteor shower will be strongest during the morning hours for observers in Asia, while in 1999 it will be best seen by observers in Asia and Europe. During the mornings of November 17 and 18 of both years observers anywhere in the Northern Hemisphere should see larger than normal displays. Start watching sometime after about 12:30 a.m. local time, which is your time. As the morning progresses, meteor rates should generally increase. Keep watching until morning twilight begins.
How Do You Observe the Leonids?
The point from where the Leonid meteors appear to radiate is located within the constellation Leo and is referred to as the radiant. The radiant is located in the western portion of that constellation in what is commonly referred to as the "sickle" or "backwards question mark." The radiant location with respect to the horizon is shown below.
(Image produced by the Author using Starry Night 2.0 and Adobe Photoshop 5.0. It represents the view from mid-northern latitudes at about 3:00 a.m. local time.)
To best observe the Leonids wear appropriate clothing for the weather. Lay outside in a reclining lawn chair with your feet pointing towards the east (the general direction of the radiant). Do not look directly at the radiant, but at the area above and around it. The Leonids can be observed into morning twilight. Other minor meteor showers will be going on at the time and stray meteors, more commonly called sporadics, will frequently be seen that do not belong to a meteor shower. When you see a meteor mentally trace it backwards and if you arrive at the "sickle" of Leo it is probably a Leonid.
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55P/Tempel-Tuttle (Comet producing Leonid meteor shower)
http://medicine.wustl.edu/~kronkg/Leonidsez.html
Copyright (c) 1998 by Tim Puckett
This image was obtained by Tim Puckett using a 60-cm f/5 Ritchey Chretien reflector and an Apogee AP-7 CCD on 1998 January 26. Twelve 300-second exposures were put together. with the first obtained at 00:31:46 UT. North is up and the field of view measures 13.87x13.87 arc minutes.
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Discovery
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Ernst Wilhelm Liebrecht Tempel discovered this comet on 1865 December 19. It was then in the evening sky near Beta Ursa Majoris. He described it as a circular object, with a central condensation and a tail 30 arc minutes long. Horace Parnell Tuttle (Harvard College Observatory, Cambridge, Massachusetts) independently discovered this comet on 1866 January 6.
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Historical Highlights
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•During the 1865/1866 apparition, the comet was only seen until 1866 February 9. Fortunately enough observations were provided to allow astronomers to determine that the comet was traveling in an elliptical orbit with a period of about 33 years. Nevertheless, the comet was not seen during its expected returns in 1899 and 1932. It was finally recovered in 1965 thanks to a painstaking examination of the orbit by Joachim Schubart (Astronomisches Rechen-Institut).
•A few years after the comet's discovery John Russell Hind made the suggestion that the comet might have previously been seen in 868 and 1366. No formal analysis was conducted until 1933, when S. Kanda took up the challenge. He concluded that the comet of 1366 was most likely Tempel-Tuttle, but the comet of 868 was not related.In 1965 Schubart took the comet's 1866 orbit and used a computed to examine the comet's motion through the solar system for 500 years into the past, applying the gravitational effects of the planets all the way. He confirmed Kanda's proof that the comet of 1366 was Tempel-Tuttle and also found that a single observation of a comet by Gottfried Kirch on 1699 October 26 was also Tempel-Tuttle. With three apparitions now available, the orbit was improved and Schubart provided a prediction for the 1965 return. The comet was recovered by Bester (South Africa) on 1965 June 30 and the position indicated that Schubart's prediction had only been 5 days too early.
•The comet's best apparition was that of 1366 when it passed 0.0229 AU from Earth--marking the third closest approach of a comet to our planet in recorded history. Astronomers have suggested the total brightness may then have reached magnitude 3. The comet passed 0.0644 AU from Earth in 1699, which marked the 18th closest approach of a comet to Earth. The brightness may then have reached 4th magnitude. The comet's last appearance in 1965 was not very favorable and it failed to exceed magnitude 16. A tail was only noticed during the 1866 apparition and even then it did not exceed 30 arc minutes, or equal to the apparent diameter of the full moon.
•J. V. Schiaparelli (Italy) wrote a letter to the Astronomische Nachrichten on 1867 February 2 which showed that this comet was probably related to the Leonid storm that was observed during November of 1833 and 1866. A comparison of the comet's orbit with that of the November 1866 Leonid stream showed an almost perfect match.
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1997-1998 Apparition
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•The comet was recovered with the Keck II 10-m reflector at Mauna Kea by Karen J. Meech, O. R. Hainaut, and J. Bauer on 1997 March 4.6. There was no trace of a coma and the nuclear magnitude was estimated as 22.5. A confirmation using the 3.6-m New Technology Telescope of the European Southern Observatory on March 7.3 also showed no trace of coma and revealed a nuclear magnitude of 22. The precise positions indicated the 1996 prediction of Donald K. Yeomans (Jet Propulsion Laboratory) required a correction of only -0.06 day.
•Although the comet was not expected to become brighter than magnitude 9.5, observers began reporting the comet was brightening faster than expected as January progressed. By mid-month many observers were already estimating the brightness as near magnitude 8, and by the 23rd observers were typically estimating it as between 7.4 and 7.8. The comet's physical appearance was typically described as very diffuse during January, with a coma diameter of between 8 and 12 arc minutes. Some larger estimates were made by observers using binoculars from regions with extremely transparent skies.
•The comet passes closest to the sun on 1998 February 28.
===
Leonid Observations:
1833 to present
http://medicine.wustl.edu/~kronkg/leonidhis.html
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History
The Leonids and the Birth of Meteor Astronomy
The night of November 12-13, 1833, not only marks the discovery of the Leonid meteor shower, but sparked the actual birth of meteor astronomy.
During the hours following sunset on November 12, some astronomers noted an unusual number of meteors in the sky, but it was the early morning hours of the 13th that left the greatest impression on the people of eastern North America. During the 4 hours which preceded dawn, the skies were lit up by meteors.
Reactions to the 1833 display are varied from the hysterics of the superstitious claiming Judgement Day was at hand, to the just plain excitement of the scientific, who estimated that a thousand meteors a minute emanated from the region of Leo. Newspapers of the time reveal that almost no one was left unaware of the spectacle, for if they were not awakened by the cries of excited neighbors, they were usually awakened by flashes of light cast into normally dark bedrooms by the fireballs.
At the time of the 1833 display, the true nature of meteors were not known for certain, but theories were abundant in the days and weeks which followed. The Charleston Courier published a story on how the sun caused gases to be released from plants recently killed by frost. These gases, the most abundant of which was believed to be hydrogen, "became ignited by electricity or phosphoric particles in the air." The United States Telegraph of Washington, DC, stated, "The strong southern wind of yesterday may have brought a body of electrified air, which, by the coldness of the morning, was caused to discharge its contents towards the earth." Despite these early, creative attempts to explain what had happened, it was Denison Olmsted who ended up explaining the event most accurately.
After spending the last weeks of 1833 trying to collect as much information on the event as possible, Olmsted presented his early findings in January 1834. First of all, he noted the shower was of short duration, as it was not seen in Europe, nor west of Ohio [Author's note: We now know the shower was seen by numerous Native American tribes throughout the midwest and western United States, who frequently referred to the event as "the night the stars fell."]. His personal observations had shown the meteors to radiate from a point in the constellation of Leo, the coordinates of which were given as RA=150 deg, DEC=+20 deg. Finally, noting that an abnormal display of meteors had also been observed in Europe and the Middle East during November 1832, Olmsted theorized that the meteors had originated from a cloud of particles in space. Although the exact nature of this cloud was not explained properly, it did lead the way to a more serious study of meteor showers.
One of the more significant findings of the 1833 Leonid storm was the determination of the meteor shower's radiant. As mentioned above, Olmsted had obtained a position, but on the same morning, Professor A.
C. Twining (West Point, New York) and W. E. Aiken (Emmittsburg, Maryland) obtained more precise estimates of RA=148.4, DEC=+22.3 and RA=148.2 deg, DEC=+23.8 deg, respectively. This was the first time a shower radiant had ever been pinpointed more precisely than a simple direction in the sky or even a constellation.
New information continued to surface following the 1833 display which helped shed new light on the origin of the Leonids. First, a report was found concerning F. H. A. Humboldt's observation of thousands of bright meteors while in Cumana, South America during November 12, 1799. Further digging around this date in other publications revealed the spectacle was visible from the Equator to Greenland. Next, in November 1834, the Leonids reappeared and, although they were not as plentiful as in the previous year, they did demonstrate that some annual activity might be present from this region. In the years that followed, Leonid displays continued to weaken. In 1837, Heinrich Wilhelm Matthias Olbers combined all of the available data and concluded that the Leonids possessed a period of 33 or 34 years. He predicted a return in 1867.
The Leonids of 1866
The interest of the astronomical world began focusing on the predicted return of the Leonids as the decade of the 1860's began. Most important was Hubert A. Newton's examination of meteor showers reported during the past 2000 years. During 1863, he identified previous Leonid returns from the years 585, 902, 1582 and 1698. During 1864, Newton further identified ancient Leonid displays as occurring during 931, 934, 1002, 1202, 1366 and 1602. He capped this study with the determination that the Leonid period was 33.25 years and predicted the next return would actually occur on November 13-14, 1866.
The expected meteor storm occurred in 1866 as predicted, with observers reporting hourly rates ranging from 2000 to 5000 per hour. The 1867 display had the misfortune of occurring with the moon above the horizon, but observers still reported rates as high as 1000 per hour, meaning the shower may have actually been stronger than in the previous year.
Another strong appearance of the Leonids in 1868 reached an intensity of 1000 per hour in dark skies.
The year 1867, marked an important development in the understanding of the evolution of the Leonids. On December 19, 1865, Ernst Wilhelm Liebrecht Tempel (Marseilles, France) had discovered a 6th-magnitude, circular object near Beta Ursae Majoris. After an independent discovery was made by Horace Tuttle (Harvard College Observatory, Massachusetts) on January 6, 1866, the comet took the name of Tempel-Tuttle. Perihelion came on January 12, 1866, afterwhich the comet began fading so rapidly, that it was not seen after February 9. Orbital calculations shortly thereafter revealed the comet to be of short period, and, as 1867 began, Theodor von Oppolzer had more precisely calculated the period to be 33.17 years. Using observations from the 1866 Leonid display, Urbain Jean Joseph Le Verrier computed an accurate orbit for the Leonids, and Dr. C. F. W. Peters, Giovanni Virginio Schiaparelli and von Oppolzer independently noted a striking resemblance between the comet and meteor stream.
After a final notable display on November 14, 1869, when hourly rates reached 200 or more, the following years were notable only due to a fairly consistent rate ranging from 10 to 15 Leonids per hour.
The Leonids of 1899
Numerous confident predictions were put forth that the Leonids would next be at their best in 1899, and an early sign of returning enhanced activity was detected in 1898, when hourly rates reached 50-100 in the United States on November 14.
What Charles P. Olivier called "the worst blow ever suffered by astronomy in the eyes of the public," was the failure of a spectacular meteor shower to appear in 1899. Predictions had been made and newspapers in Europe and America made the public well aware that astronomers were predicting a major meteor storm. Although the "storm" failed to appear, the Leonids did possess maximum hourly rates of 40 on November 14---at least indicating some unusual activity. Later investigations revealed the stream to have experienced close encounters with both Jupiter (1898) and Saturn (1870), so that the stream's distance from Earth in 1899 was nearly double that of the 1866 return.
As it turned out, the actual peak of activity for the Leonids came on November 14-15, 1901. In the British Isles, Henry Corder (Bridgwater), E. C. Willis (Norwich) and others reported hourly rates as high as 25 before morning twilight interfered. Several hours later, the Leonid radiant was well placed for observers in the United States, and it was apparent that the activity had increased. On the east coast, Olivier (Virginia) and Robert M. Dole (Massachusetts) independently obtained hourly rates of 60 and 37, respectively. By the time the Leonids were visible over the western half of the United States, they had apparently reached their peak. At Carlton College (Minnesota) it was estimated that individuals could have counted about 400 per hour. E. L. Larkin (Echo Mountain, California) estimated that rates reached a maximum of 5 per minute (300 per hour). By the time the British Isles had the radiant back in view, hourly rates had apparently declined to about 20. After analyzing the available data, William F. Denning concluded that the maximum of this shower came on November 15.48 Greenwich Mean Time (November 15.98 UT).
The Leonids were barely detected in 1902, due to moonlight, but there was a reappearance in 1903. On November 16, Denning estimated a maximum hourly rate of 140, and said that for 15 minutes following 5:30 a.m.
(local time) meteors were falling at 3 per minute. From plotted meteor paths, he found the radiant to have been 6 degrees in diameter, centered at RA=151 deg, DEC=+22 deg. John R. Henry (Dublin, Ireland) was also surprised by the intensity of the display, and he noted maximum rates near 200 per hour. Henry further noted that, at maximum, the Leonid meteors were pear-shaped and left rich trains. He noted, "Other members of the star shower dissolved in bright streaks, or made their appearance as vivid flashes of light...." Finally, Alphonso King (Sheffield, England) did not begin observations until 5:57 a.m. He noted that 18 Leonids were seen in the first five and a half minutes, while only 16 were seen in the next half hour. King plotted 10 meteors which indicated a radiant of RA=148 deg, DEC=+22 deg. From the above observations, it would seem the 1903 maximum came on November 16.2 UT.
The Leonids of 1932-1933
The Leonids returned to normal in the years following 1903, with hourly rates ranging from 5 to 20 (average about 15). Despite having miscalculated the Leonid maximum in 1899, astronomers began to make predictions for the next return---the most likely date being 1932.
Enhanced activity began early when, in 1928, maximum hourly rates reached 50 or more. During 1929, rates were lower, only 30 per hour, but moonlight was then a factor. During this latter year, members of the American Meteor Society (AMS) made fairly extensive observations, and Olivier's analysis revealed a radiant diameter of 5-6 degrees and a shower duration of 8-10 days.
The Leonids began to show great strength in 1930. Professor C. C. Wylie (Iowa City, Iowa) estimated maximum hourly rates of 120 shortly before dawn on November 17. Olivier said the shower contained "many brilliant meteors with long enduring trains." His analysis showed Leonids were first observed on November 13/14 and last seen on the 22nd. He confirmed that rates were "considerably over 100 per hour, despite moonlight...." The 1931 display showed a slight increase over 1930, but certainly not as great as expected considering the lack of moonlight. Olivier's analysis of AMS observations revealed rates between 130 and 190 per hour for observers in the United States during the pre-dawn hours of November 17.
The predicted meteor storm of 1932 was looked for with great anticipation by astronomers, but it had been realized that moonlight would interfer with observations. Nevertheless, the first detection of the rapid rise to maximum came at Helwan Observatory (Egypt) during the pre-dawn hours of November 17. P. A. Curry was one of seven observers keeping a lookout for the expected storm, and the greatest hourly rates reached 51; however, it should be noted that the 5-minute counts showed a steady rise to 9 at 4 a.m.---amounting to 108 per hour---followed by a rapid decrease in numbers thereafter. Members of the Bribut it had been realized that moonlight would interfer with observations. Nevertheless, the first detection of the rapid rise to maximum came at Helwan Observatory (Egypt) during the pre-dawn hours of November 17. P. A.
Curry was one of seven observers keeping a lookout for the expected storm, and the greatest hourly rates reached The Leonids seemed to decline slower than normal after 1932, as maximum rates remained between 30 and 40 meteors per hour from 1933 through 1939. This meant that greater than normal activity persisted from 1928 to 1939, or 12 years. The previous periods of enhanced activity occurred during 1898-1903, 1865-1869 and 1831-1836, which amounted to only 5 or 6 years.
The Leonids of 1966
Throughout the 1940's and 1950's hourly rates retained their "normal" character of 10-15 per hour. However, the period was highlighted by a new advance in astronomy---radar studies. Jodrell Bank Radio Observatory was the first station to detect the Leonids, with maximum observed rates being 24 in 1946, but only 3 to 11 during the period of 1947 to 1953.
Unfortunately, due to the weakness of the Leonids during the 1950's, the increasing sophistication of the equipment still could not obtain information such as radiant positions or radiant diameters.
Visual observers generally ignored the Leonids during the late 1950's, and this state of neglect caused many to completely miss the unexpected arrival of enhanced activity in 1961. Dennis Milon was one of five amateur astronomers observing outside Houston, Texas, when 51 Leonids appeared between 3:10 and 4:10 a.m. on November 16 (about November 16.4 UT). The next morning the greatest one-hour interval produced a rate of 54 Leonids (about November 17.4 UT), bringing the Texas group to believe maximum had probably occurred late on the 16th. Similar rates were reported elsewhere. Norman D. Petersen (California) commented that the Leonids were blue-white, very rapid, and often left long-enduring trains 10 degrees in length.
The 1962 and 1963 displays were about normal with hourly rates of 15 or 20, while the 1964 display perked up with enhanced rates of 30 per hour.
During 1965, observers in Hawaii and Australia were treated to one of the best displays since 1932. From the Smithsonian tracking station at Maui (Hawaii) hourly rates were near 20 on November 16.56 UT, but increased to about 120 by November 16.64 UT. Meanwhile, observers at the Smithsonian tracking station at Woomera (Australia) reported 38 Leonids of an average magnitude of -3 between November 16.65 and 16.77 UT.
Although astronomers were still a year away from the predicted Leonid maximum, optimism did not run high concerning the appearance of a meteor storm. Judging by the 1899 and 1932 returns, the stream orbit had obviously been perturbed so that a close encounter with Earth's orbit seemed no longer possible. About as far as astronomers were willing to gamble was to say that rates would probably be greater than 100 per hour. For much of the world, this is the best that was seen, but for the western portion of the United States, it was a night to be remembered.
On the night of November 17, 1966, expectations were high worldwide, but few observers got to see the Leonids as well as Dennis Milon and a dozen other amateur astronomers situated under the clear skies of Arizona.
Observations began at 2:30 a.m. (November 17.35 UT) and 33 Leonids were detected during the next hour. After a short break, the next hour began at 3:50 a.m., with 192 Leonids being observed. The team had been keeping magnitude estimates during the early part of the shower, but this ended around 5:00 and, by 5:10, the observers were detecting 30 meteors every minute, but the display was far from over. Rates at 5:30 were estimated as several hundred a minute and the team estimated a peak rate of 40 per second was attained at 5:54 (November 17.50 UT)! The activity declined thereafter, and by 6:40 it was down to 30 per minute, despite the fact that astronomical twilight had begun 9 minutgot to see the Leonids as well as Dennis Milon and a dozen other amateur astronomers situated under the clear skies of Arizona. Observations began at 2:30 a.m (November 17.35 UT).
The major peak of the 1966 display was also enjoyed by observers in New Mexico, Texas, and California. Observers in the two former states were somewhat hampered by twilight, but observers in California may have had the best view though not as well publicised as the Arizona observations at the time. When Table Mountain Observatory's assistant astronomer James Young began his observations at 2:30 a.m. (local time) heavy clouds were present, but conditions had greatly improved by 3:30. From that time on Young and the four other observers present watched as meteor rates continued to climb. By 4:45 a.m. (local time) the group decided rates had reached about 50 per second, with this intensity being maintained for about 10 minutes before a noticeable decline had set in.
By the time twilight had begun the group had photographed over 1000 meteor trails, including about a dozen fireballs! Observers in the eastern portion of the United States did report rates of several hundred per hour, but other countries reported rates generally less than 200 per hour, since maximum had occurred during daylight. An exception was observers at a USSR polar arctic station, who were able to monitor the shower at its peak. With the radiant only 8 deg above the horizon, the report from two observers said, "there was a continuous flight of meteors in a single direction, from north to south.
Some appeared in the zenith and curved over the southern horizon, some appeared from the northern horizon and disappeared in the zenith, and some flew across the entire horizon, leaving behind a bright trail." R.
L. Khotinok's analysis of the complete report revealed an observed maximum rate of 20,000 per hour, while a correction for the low altitude gave a rate of 130,000 per hour---agreeing quite well with the Arizona and California observations.
In the years following the 1966 display, hourly rates for the Leonids remained high. From 1967 through 1969, observers continued to detect rates of 100-150 per hour. After a return to normality in 1970 (15 per hour), rates jumped to 170 per hour in 1971 and 40 in 1972. The Leonids have remained between 10 to 15 per hour at maximum ever since.
One of the first Leonid studies involving an analysis of observational data, was published in 1932 by Alphonso King. The study was basically a look at his observations made during 1899-1904 and 1920-1931. King noted the diameter of the radiant to generally be less than 4 deg, and he determined a radiant ephemeris which indicated a daily motion of +1.0 deg in RA and -0.4 deg in DEC.
Some of the more interesting recent studies of the Leonids involved extensive observations by professional and amateur astronomers in the Soviet Union during 1971 and 1972. The first set of observations were made at Sudak and Simferopol during November 15-19, 1971. Although numerous observers participated, it was the more experienced observations of N. V. Smirnov and Yu. V. Lyzhin which were evaluated.
Some of the various observed aspects of the meteors included 553 meteors with an average magnitude of 3.40 and 171 color estimates indicating 74% were green, 20% were white, 1% were blue and 1% were orange. One of the most striking discoveries was the detection of multiple radiants.
Although six radiants were determined, the most active was the long-known radiant at RA=151.7 deg, DEC=+22.9 deg (based on 222 plotted meteors) and the authors noted that the total plots indicated activity primarily came from an area 2.5 deg x 8 deg centered on this radiant.
The 1972 visual survey was conducted during November 16-18, from the same locations given above. A magnitude breakdown was not given strictly for the Leonids, but for all meteors observed at Sudak. The average brightness ended up as 3.01 for 576 meteors, of which 335 were Leonids.
On this occasion, six radiants were again determined from plots, with the main center being at RA=151.9 deg, DEC=+22.7 deg (based on 185 meteors). The radiants were generally grouped into an area about 10 deg across; however, it should be noted that two radiants within this area were distinctly detected in both years---one near Mu Legiven above. A magnitude breakdown was not given strictly for the Leonids, but for all meteors observations.
During 1967, one of the first mathematical surveys of the perturbations suffered by the Leonid meteor stream was conducted. Using the orbit determined for the 1866 Leonid shower, E. I. Kazimirchak-Polonskaya, N.
A. Belyaev, I. S. Astapovich and A. K. Terent'eva examined 12 hypothetical meteor groups situated around the orbit. One of the major findings was that Jupiter and Saturn were primarily responsible for altering the encounter conditions between Earth and the meteor stream.
Earth itself was even found to have a strong effect on meteor bodies passing within several thousand kilometers of its surface by shortening the revolution period by several years, strongly altering the eccentricity and even changing the inclination.
The Leonids of 1998-1999
The most ambitious study of the relationship between Tempel-Tuttle and the Leonids was published in 1981. Donald K. Yeomans (Jet Propulsion Laboratory, California) mapped out the dust distribution surrounding Tempel-Tuttle by "analyzing the associated Leonid meteor shower data over the 902-1969 interval." He noted that most of the ejected dust lagged behind the comet and was outside its orbit, which was directly opposite to the theory of outgassing and dust ejection developed to explain the comet's deviation from "pure gravitational motion." Yeomans suggested this indicated "that radiation pressure and planetary perturbations, rather than ejection processes, control the dynamic evolution of the Leonid particles." Concerning the occurrence of Leonid showers, Yeomans said "significant Leonid meteor showers are possible roughly 2500 days before or after the parent comet reaches perihelion but only if the comet passes closer than 0.025 AU inside or 0.010 AU outside the Earth's orbit." He added that optimum conditions will be present in 1998-1999, but that the lack of uniformity in the dust particle distribution still makes a prediction of the intensity of the event uncertain.
The Leonids began drawing the attention of observers shortly after the 1990's began, but notable activity did not appear until 1994. In that year both visual and radio-echo observers detected rates that were above normal on the night of November 17-18, with an analysis by Peter Jenniskens indicating a short burst with a ZHR of 70 to 80. Observers worldwide covered the 1995 return quite well. The period of maximum was rather broad and lasted about 24 hours, with the maximum ZHR reaching about 35; however, there was a short-lived outburst which produced about 50 per hour a few hours before the normal maximum. Observations obtained during 1996 indicated a maximum ZHR of about 60 per hour, with numerous fireballs present.
The latest observations of the Leonids occurred in strong moonlight on November 17, 1997, when numerous observations were reported worldwide.
Observers indicated a peak zenithal hourly rate of between 80 and 150, around 10:50 UT on the 17th. The wide scatter was attributed to the moonlight-affected seeing. Numerous fireballs were seen. The Author observed a spectacular -5 fireball that lit up the sky when it suddenly flared to a magnitude of between -10 and -12. It left a glowing train that lasted over four minutes and became distorted by high-altitude winds. Other observers reported numerous fireballs in the range of -6 to -9. The Central Bureau for Astronomical Telegrams reported that a possible secondary peak in activity occurred during the period of 16:45 to 21:30 UT on the 17th. This latter "peak" was detected by monitoring the 50MHz HAM radio signals.
Conclusions
As indicated by Yeomans in 1981, inconsistencies within the dust cloud surrounding comet Tempel-Tuttle are expected. The particles encountered during the period of 1994-1996 are those that were probably released by the comet a few hundred years ago and have had time to disperse.
Obviously as the comet gets closer to the sun, the pTempel-Tuttle are expected. The particles encountered during the period of 1994-1996 are those that were probably released by the comet a few hundred years ago and have had time to disperse. Obviously as the comet gets closer to the sun, the particle
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The meteor shower pages have been accessed: 341194 times since November 6, 1995
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Leonids: 1966 Recollections
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Although astronomers do not expect this year's Leonid meteor shower to reach the same intensity as in 1966, the 1966 display certainly deserves extra attention as it was one of the strongest meteor storms in history. Although three decades have passed, there are plenty of people who still have very strong recollections of the 1966 display, which occurred during the early morning hours of November 17. Here are a few that have been sent to the Author.
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Ed Cunnius was six-years old in 1966 and living on his parent's ranch in north Texas. He related the following account to me in October 1998--
My mom woke me up that morning and told me to put on a coat and come outside. I don't know the exact time. We normally had to get up at six o'clock, and it was well before then--probably around five. I couldn't imagine what was going on, but it had to be something pretty exciting if I could wear my pajamas outside. As I ran out of the house, I remember my dad standing in the yard, quietly staring at the sky. I could see the reason even before I was completely out the doorÑthe sky was covered with meteors, all seeming to rain straight down. My dad explained that this was a "meteor shower" and that my grandfather had called to wake us up so we could see it. Facing east, I looked up and into the "center" of the storm where the meteors were so fast and constant it looked as if the earth were rushing through the stars. As it began to get lighter and the sky turned from black to dark blue; a gigantic fireball fell in the west leaving a visible smoke trail. It was bright enough to overpower the predawn sky-glow, turning the whole sky a pale blue-green. We watched until the sun came up. I don't remember the rates tapering off much, just that the very faint meteors became harder and harder to see. All morning faint, short-tailed meteors had provided a kind of scratchy background to the brighter rain of material. From that night on, anytime the weatherman announced a meteor shower was on the way, I would fully expect another spectacle like the Leonids. I was jaded at the age of six by the storm of the century.
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Susan Hensz was living with her family in Harlingen, Texas in 1966. She related the following account to me in October 1998--
I was awakened by my father at approximately 2:30am. He was frantic that I arise and "come watch. It's like the sky is falling!!" He was right! I had never seen so many trails. Seemed to me that every star in the heavens was headed "south". Also, it seemed that they were in every part of the sky, not confined to a single area, but in every direction we looked. Unhampered by bright city lights, it was breathtaking. My present boss was in Pharr, Texas in 1966 and when I mentioned the 1966 event and the upcoming activity, he and I compared recollections - basically he says the same thing..."they were everywhere."
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James W. Young was then an assistant resident astronomer at Jet Propulsion Laboratory's Table Mountain Observatory in 1966. Table Mountain Observatory is located some 45 miles northeast of Los Angeles, at an elevation of 7500 feet. He related the following account to me in November 1996--
The 1966 Leonid Meteor Shower was observed ... on the morning of November 17 starting at 2:30 AM through heavy clouds. By 3:30 AM, the clouds had completely cleared while the intensity of the shower continued to grow.
Around 4:45 AM the shower seemed to peak with the sky filled with meteor trails everywhere! The estimated peak of 50/second lasted for about 10 minutes. During the event, as observed by the five members present, we photographed over 1000 meteor trails, including a dozen fireballs, the brightest one being -12 magnitude! A total of 22 fireballs were seen by the group. During the peak, everyone felt like we needed hard-hats, as the intensity was so great when we blinked our eyes open (instead of closed), the sky was full of streaks everywhere!
Most of the lower areas in southern California were fogged in at the time, and only a few reports from local truckers were reported along with ours in California.
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Toshiyuki Ishikawa was an officer aboard a fishing boat in 1966. On the night of the Leonids the boat was in the Pacific Ocean, just off the coast of Baja California. They were out of sight of land. His son related the following story to the Author in December 1996--
The night watch on the night noticed the great meteor activity and when the peak was approaching could not hold it to himself and began banging on the doors of the boat crew to tell them to come out of the sleep and go outside and watch the show in the sky.
According to my father, the unobstructed view from the boat (boat usually darkens the illumination during the ocean voyage so that they can adjust to the darkness) gave the crew sepctacular view of many bright meteors. He told us that some meteors were as bright as half, or full moons and every time such meteors flew, the ocean surrounding the boat reflected back the light as if it were daytime and it was surreal experience for the crew. (This reflection from the ocean of the meteor light is something I had not read before in Astronomy books.) Anyway, they were so surprised and a telegram was sent to the Tokyo astronomical observatory to report this unusual observation.
Later while he was still away from home on the voyage, someone at the observatory sent us a very detailed courteous letter explaining that it must have been the leonid shower what the boat crew saw. I was small like 3rd grader and didn't read the letter myself.
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Leonids: Observer's Synopsis
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The duration of this meteor shower covers the period of November 14-20. Maximum currently occurs on November 17 (solar longitude=235 deg), from an average radiant of RA=153 deg, DEC=+22 deg. Although the maximum hourly rate typically reaches 10-15, this shower is most notable for producing greatly enhanced activity every 33 years---events that are associated with the periodic return of comet Tempel-Tuttle. During these exceptional returns, the Leonids have produced rates of up to several thousand meteors per hour. The Leonids are swift meteors, which are best known for producing many exceptionally bright meteors that leave a high percentage of persistent trains. The radiant's daily motion is +1.0 deg in RA and -0.4 deg in DEC.
Leonids: How to Observe
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The point from where the Leonid meteors appear to radiate is located within the constellation Leo and is referred to as the radiant. The radiant is located in the western portion of that constellation in what is commonly referred to as the "sickle" or "backwards question mark." The radiant rises around 12:30 a.m. local time. Although a few Leonids can be observed prior to this, more will be seen after it rises. At about 3:00 a.m. the radiant is about 30 degrees above the horizon. The radiant location with respect to the horizon is shown below.
(Image produced by the Author using Starry Night 2.0 and Adobe Photoshop 5.0. It represents the view from mid-northern latitudes at about 3:00 a.m. local time.)
To best observe the Leonids wear appropriate clothing for the weather. Lay outside in a reclining lawn chair with your feet pointing towards the east (the general direction of the radiant). Do not look directly at the radiant, because meteors directly in front of you will not move much and fainter ones might be missed. Instead, keep your center of gaze about 30 or 40 degrees above or west of the radiant. The Leonids can be observed right on into morning twilight, especially during years of enhanced activity, i.e., 1998 and 1999. Other minor meteor showers will be going on at the time and stray meteors, more commonly called sporadics, will frequently be seen that do not belong to a meteor shower. When you see a meteor mentally trace it backwards and if you arrive at the "sickle" of Leo it is probably a Leonid.
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Leonid Observations: Ancient and Medieval
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[Under Construction]
The Leonids have been well-observed for over 1000 years. But strong interest in discovering the nature of meteor showers really did not begin until the great 1833 display of the Leonids. In the years following the 1833 display research increased and several astronomers began looking for previous appearances of the Leonids and other meteor showers among ancient and medieval documents. In 1841 Edward C. Herrick published a paper that linked a few of the then-known annual meteor showers to pre-19th century displays. In 1864 Hubert A. Newton published a paper that offered the first elaborate catalog of pre-19th century displays of the Leonids.
A significant addition to our knowledge of the ancient and medieval Leonid displays came in 1958 when Susumu Imoto and Ichiro Hasegawa published a list of meteor shower accounts obtained from Chinese, Japanese, and Korean historical texts.
For the last several years I have been conducting extensive research to find ancient and medieval accounts of comets. Along the way I found numerous records of meteor showers, several of which were obviously Leonids.
What follows may be the most comprehensive catalog of pre-19th century Leonid displays. I will be adding to it in the near future. Right now I have tried to group the observations with the probable perihelion date of the Leonids' parent comet Tempel-Tuttle to help illustrate how the intensity of the meteor shower apparently increases when the comet is in the inner solar system.
Please note that because of the gravitational influences of the planets, there has been a steady advancement of the line of nodes of Tempel-Tuttle. This basically means that the point where Earth intersects the comet's orbit occurs later every century. Therefore, the Leonids occurred in mid-October during the 10th century, late October during the 16th century, and mid-November during the 20th century.
The perihelion dates of Tempel-Tuttle were kindly computed and supplied to the author by D. K. Yeomans of JPL.
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Comet Tempel-Tuttle Passed Perihelion in 901 September 28
901: The historian Eutychius of Alexandria (877-940) included an interesting account in his text Annals. The accounts sounds like what would be expected for the Leonids, although the date is about 12 days later than would be expected (dating error?). He said, "In Egypt in the morning of Wednesday, 9 Dhu al-Qa`da (Oct. 26) during the latter half of the night until the morning, the stars were very disturbed--which are called shooting stars. The heavens were filled with starry shooting stars scattered east and west, south and north. No one was able to gaze at the heavens because of the numerous starry shooting stars."
902: "In the month Dhu al-Qa`da of the year 289 (of the Hegira) died king Ibrahim ben Ahmet, and during the same night were seen great numbers of star, which moved, as if they had been darted through the atmosphere, from a culminating point, and rushed down on the right and left, like rain. On account of this phenomenon, this year was called the year of stars."
The Italian text Chronicon, which was written around 1178 by Romualdus, notes that on the night of October 13, 902, people in Taormina, Sicily, "saw small starlike fires moving to and fro through the air..."
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Comet Tempel-Tuttle Passed Perihelion in 935 January 24
931: The Chinese text Ssu-Tien-Khao records that on October 15, 931, "Many stars flew, crossing each other," while on October 16, "Many stars flew and fell."
934: The Chinese text Liao-Chih-Pen-Chi records that on October 13, 934, "Stars flew like a shower in the southwest."
The Chinese text Ssu-Tien-Khao records that on October 14, "Many stars flew, crossing each other"
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Comet Tempel-Tuttle Passed Perihelion in 968 March 15
967: The Japanese text Nihon Kiryaku records that on October 14, 967, "Stars scattered from the northeast to the southwest all night."
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Comet Tempel-Tuttle Passed Perihelion in 1001 June 8
1002: The Chinese text Thien-Wen-Chih records that on October 12, 1002, "Scores of small stars fell."
The Japanese text Nihon Kiryaku records that on October 14, "Meteors flew from the northeast to the southwest at midnight," while on October
15, "Meteors flew early in the morning."
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Comet Tempel-Tuttle Passed Perihelion in 1035 January 6
1035: The Japanese text Fuso Ryakki records that on October 14, 1035, "Meteors appeared in the morning."
1037: The Japanese text Fuso Ryakki records that on October 14, 1037, "Meteors appeared at midnight."
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Comet Tempel-Tuttle Passed Perihelion in 1069 March 4
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1102 June 25
1101: The 12th century French text Chronicon Sancti Maxentii records that on October 17, 1101, "stars were seen to fall from the sky."
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Comet Tempel-Tuttle Passed Perihelion in 1135 March 3
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1167 November 29
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1201 January 14
1202: Several Muslim historians writing during the 13th and 14th centuries describe a significant meteor shower seen around mid-October of 1202. Al-Dhahabi (1274-1348) wrote in Siyar a'lam al-nubala', "the stars were disquieted and flew like the flight of locust. This continued until the dawn and the people were terrified and they made haste with prayers."
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Comet Tempel-Tuttle Passed Perihelion in 1234 October 29
1237: The Japanese text Azuma Kagami records that on October 19, 1237, "Meteors appeared in the morning."
1238: The Japanese text Konendai Shiki records that on October 18, 1238, "Countless large and small meteors appeared with white-red color at midnight."
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Comet Tempel-Tuttle Passed Perihelion in 1268 January 8
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1300 November 15
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1333 September 12
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1366 October 18
1366: The Portuguese text Cronicas dos reis de Portugal (1600) records that on the morning of October 23 "there was in the heavens a movement of stars, such as men never before saw or heard of. From midnight onward, all the stars moved from the east to the west; and after being together, they began to move, some in one direction, and others in another. And afterward they fell from the sky in such numbers, and so thickly together, that as they descended low in the air, they seemed large and fiery, and the sky and the air seemed to be in flames, and even the earth appeared as if ready to take fire. Those who saw it were filled with such great fear and dismay, that they were astounded, imagining they were all dead men, and that the end of the world had come."
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Comet Tempel-Tuttle Passed Perihelion in 1400 May 20
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1433 July 30
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1466 July 31
1466: The Japanese text Gohokkoin Shokaki records that on October 22,
1466, "Meteors flew from the southwest to the northeast."
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Comet Tempel-Tuttle Passed Perihelion in 1499 September 6
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1533 February 25
1532: The Korean text Yollsong Sillok records that on October 24, 1532, "Stars flew like a shower."
1533: The Korean text Yollsong Sillok records that on October 24, 1533, "Stars flew like a shower in all directions."
The Chinese text Thien-Wen-Chih records that on October 24, "Countless large and small meteors flew in all directions crossing each other till dawn."
The Japanese texts Konendai Shiki and Taiseiki record that on October 25, "Many stars flew in the hemisphere and fell on land and sea."
1538: The Korean text Yollsong Sillok records that on October 26, 1538, "Meteors appeared in all directions."
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Comet Tempel-Tuttle Passed Perihelion in 1567 March 13
1554: The Korean text Yollsong Sillok records that on October 24, 1554, "Meteors appeared at intervals."
1566: The Korean text Munhon-Piko records that on October 26, 1566, "Meteors flew like a shower in all directions."
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Comet Tempel-Tuttle Passed Perihelion in 1600 July 20
1602: The Chinese text Thien-Wen-Chih records that on November 6, 1602, "Hundreds of large and small stars flew, crossing each other." The Korean text Munhon-Piko records that on November 11, "Many stars flew in all directions."
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Comet Tempel-Tuttle Passed Perihelion in 1633 June 21
1625: The Korean text Yollsong Sillok records that on November 4, 1625, "Meteors appeared in the whole sky."
The Korean text Munhon-Piko records that on November 5, "Many stars fought in the west."
The Korean text Yollsong Sillok records that on November 6, "About ten meteors appeared in midair."
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Comet Tempel-Tuttle Passed Perihelion in 1666 June 5
1666: The Chinese text Thien-Wen-Khao-Ku-Lu records that on November 7,
1666, "A great star fell. A small star followed." [The actual date was given as November 8 and Imoto and Hasegawa presumed this was an error].
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Comet Tempel-Tuttle Passed Perihelion in 1699 October 10
1698: The Japanese text Shinzan-Shu records that on November 8, 1698, "Meteors fell like the weaving (a shuttle?)."
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Comet Tempel-Tuttle Passed Perihelion in 1733 October 1
No Recorded Meteor Showers
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Comet Tempel-Tuttle Passed Perihelion in 1767 February 24
No Recorded Meteor Showers
===
