Annual Review 2000
By Alastair McBeath
We expected 2000 to be a difficult year, since many favourite major shower maxima were going to suffer from bright moonlight during it, and the lower visual observing hours total than in 1999 reflects this especially. It was typical this should happen in a year which the SPA Cloudwatch project (now run by Terry Holmes) recorded its best tally of clearer nights across the country for nearly 20 years! The visual meteor numbers naturally suffered too thanks to there being no Leonid storm, which had so massively boosted our totals in 1999. Even the radio observers endured one of the worst years for interference in a long time, including Sporadic-E in May-August and aurorae at a few most inconvenient times (including on August 12!). However, the year will be more positively remembered for its unusual crop of sometimes widely-seen fireballs, a splendid run of clearer nights right across the Perseids in July-August, the strong Leonid showing in November, and of course, the interesting observing circumstances the Moon so often created.
Grand Totals and Observers
The overall totals for the various observing techniques were: Visual - 746.4 hours, 10,535 meteors; Photographic - 875.6 hours, but sadly no trails reported; Radio - 59,979.4 hours; Video - 2279.7 hours, 11,429 trails. The visual, photographic and video tallies were particularly added to by data from the German Arbeitskreis Meteore (AKM) observers, details of which were taken from the AKM's monthly journal Meteoros provided by Ina Rendtel. Especially active AKM observers included Frank Enzlein, Sven Naether, Juergen Rendtel, Roland Winkler and Oliver Wusk (with between 40-135 hours of visual observing each for the year). Most of the radio data came from the Radio Meteor Observation Bulletins (RMOBs), which Chris Steyaert in Belgium submitted. Reports, ideas, suggestions and comments have come from other observing and non-observing Section correspondents too, which have all helped to complete the picture of meteor activity during the year as presented in the regular SPA News Circular columns and SPA Electronic News Bulletins, our results articles published in the International Meteor Organization's (IMO's) bimonthly journal WGN, our Website reports, three of which are supplementary to this Review (including those on the January 9 bolide, the Perseids and the Leonids), and this Review itself. All contributions are again most gratefully acknowledged.
The list of people providing observational data at times outside those covered by the supplementary reports, excluding those who only provided casual fireball details, follows. All are to be congratulated and thanked for their time and trouble in observing and submitting their data, without which the Section could not continue to function. The listing contains the country most observations were made from, with abbreviations indicating the type of observing carried out. "P" denotes photographic, "R" radio, "Vi" video, and "V" that visual results were also contributed by that person. Observers without an additional letter provided purely visual data:
Jean-Louis Aillaud (RMOB, Reunion Island, Indian Ocean; R), Enric Fraile Algeciras (RMOB, Spain; R), members of the AKM (Germany; P/Vi/V), Dirk Artoos (Belgium; R), Mike Boschat (RMOB, Canada; R), Jay Brausch (USA), Chris Chambers (England), Dee Choudhury (England), Mary Cook (England), Tim Cooper (South Africa), Patrick Delacorte (RMOB, France; R), Maurice de Meyere (RMOB, Belgium; R), Del Dobberpuhl (RMOB, USA; R - with John and Jack Meyer), Steve Evans (England; Vi), Didier Favre (RMOB, France; R), Ghent University (RMOB, Belgium; R), Shelagh Godwin (England), Roberto Gorelli (Italy), Rafael Haag (RMOB, Brazil; R), Lucy Hague (Scotland), Philip Heppenstall (England), Albert Heyes (England; R - with John Blakeley and Jim Leviston), Will Kelsey (RMOB, USA; R), Werfried Kuneth (RMOB, Austria; R), Marco Langbroek (Netherlands), Bob Lunsford (USA), Alastair McBeath (England), R B Minton (USA; R), Koen Miskotte (Netherlands), Hiroshi Ogawa (RMOB, Japan; R), Sadao Okamoto (RMOB, Japan; R), Trevor Pendleton (England), Ton Schoenmaker (RMOB, Netherlands; R), George Spalding (England), Dave Swan (RMOB, England; R), Ervin Szlanicska (RMOB, Slovakia; R), Istvan Tepliczky (RMOB, Hungary; R), Pierre Terrier (RMOB, France; R), Garfield Tsao (RMOB, Taiwan; R), Bruce Young (RMOB, Australia; R), Ilkka Yrjola (RMOB & AKM, Finland; R, Vi).
The leading UK visual observers managed between 30-65 hours of watching each during the year, more than in 1999, but comparable to the totals in 1998. Elsewhere, and aside from the AKM observers mentioned earlier, few watchers managed much more than 20 hours. The overall impression from observers was that they enjoyed what meteoric events they were able to follow, even when the Moon was strong, which impression was a particular bonus in such a difficult year. Four radio operators covered 250+ days during the year, with four more amassing over 200 days' worth of data.
Highlights of the Year
Quadrantids: (See also News Circular 213 and our results article in WGN 28:6 (2000 December), pp. 232-236) January 3-4 brought the highest Quadrantid ZHRs, as expected, with a visual peak around 03h-05h UT (ZHR = 125 +/- 20). The predicted time was around 05h-06h UT. This peak was recorded less strongly in the radio results than another at around 09h-11h UT however, and there is a small amount of visual data which suggests ZHRs may have risen again to ~ 70 +/- 10 by 11h UT over the USA at least. Too few visual reports were available across the shower to say whether a dual peak definitely occurred in 2000 or not, but this will be something to check for in coming years.
January 9 Fireball: For details, see News Circulars 212 & 213, our results article in WGN 28:6 (2000 December), pp. 232-236, but especially the SPA Meteor Section Report: Brilliant Bolide Over UK, January 9, 2000 on this Website.
Tagish Lake Meteorite Fall, 2000 January 18: (See also News Circular 215 and references in item 11 of our "Recent Publications" list in the Annual Review 1999) A spectacular fireball which passed over northwestern Canada at 16h43m UT dropped numerous carbonaceous chondrite meteorites onto the frozen surface of Tagish Lake, Yukon Territory and the surrounding area, many of which were later recovered by search teams during the spring thaw. Far more others doubtless dropped to the lake bed as the ice melted. Around 10 kg of material was recovered, though it is estimated the pre-atmospheric mass of the whole body was about 200 tonnes. Video observations meant a useful orbit could be determined, only the fifth such meteorite orbit to be obtained to that time, indicating it had a low inclination and passed from just inside the Earth's orbit to the outer parts of the asteroid belt between Mars and Jupiter.
January Coma Berenicids - Possible New Shower?: (See also our results article in WGN 28:6 (2000 December), pp. 232-236, items in Electronic News Bulletins 64 (2000 December 24) and 67 (2001 February 5), and the article by Roberto Gorelli and myself on pp. 190-191 of WGN 28:6 (2000 December)) Unusual activity around January 24-25 was first suspected in SPAMS data in 1998 (see our Annual Review 1998), and it now seems a minor radiant in Coma Berenices may be active between January 20-26 at least, from results made in 2001 and based on previous years' data now available. The catalyst to realizing where the radiant might be came in late 2000, while radio results in 1999 and 2000 January suggested the shower may be periodically more active, though still minor. Observations are urged in all future years certainly.
February 11-14 Fireballs: (See also News Circulars 213 & 215 and our results article in WGN 28:6 (2000 December), pp. 232-236) A loose "cluster" of four fireballs started at 02h40m UT on February 10-11, with a magnitude -6/-8 event over the English Channel as seen from the Dorset coast (both witnesses also heard simultaneous hissing sounds as the fireball flew over). Four hours later around 06h45m UT a full-Moon bright fireball was seen low to the north-west from the north Midlands by a driver. On February 13-14 near 18h21m UT, another driver and companion spotted a slow, bright fireball near Sirius from north of the Firth of Forth. The final event was between 17h45m-17h50m UT on February 14-15, spotted by ten witnesses in central and eastern Scotland, suggesting the fireball tracked south-east to north-west over central Scotland, but the reports were too sparse to allow a proper track to be determined.
Plotted Virginid Radiants: (See also our results article in WGN 28:6 (2000 December), pp. 237-239) Sadly, although 71 meteors were plotted during our spring meteor plotting project, no clear radiants were revealed in 2000 to add to the data already collected by SPAMS watchers since 1988. Of course, we need to keep making such plots over a long period to help overcome problem years like this these, so send an A5-sized SAE to our Assistant Director Shelagh Godwin, (whose address is in the News Circulars, for your meteor plotting pack if you have not yet done so (which includes details on our late-year Aurigid and Taurid plotting project too).
March-April Fireballs: (See also News Circular 215 and our results article in WGN 28:6 (2000 December), pp. 237-239) Three events were seen over the opening weekend in March, the first around 22h00m-22h05m UT on March 4-5, a magnitude -6/-9 slow, green meteor, noted from three sites in south Wales and south-west England, the second near 18h10m UT on March 5-6, of magnitude -5/-8, as reported from two locations in south-west Scotland, and the final event about 2.5 hours later, ~ 20h20m-20h30m UT, observed from two places in central-southern Scotland, possibly of magnitude -6/-10. Sky positions for this last object inferred it probably passed high over north-eastern Scotland. On March 18-19, four witnesses at two separate sites in Fife and north Wales caught a magnitude -5/-10, slow, green fireball around 19h40m UT, which most likely passed over northern England or just offshore from there above the North Sea. Then on the evening of April 5-6, another brilliant green meteor, perhaps over the northeastern Irish Sea, was reported via media sources. Unfortunately, no eye-witness records could be secured, so no further details, not even a rough timing, could be established for it.
Lyrids: (See also News Circular 215 and our results article in WGN 28:6 (2000 December), pp. 237-239) Full Moon on April 18 meant 2000 was not a good year for visual Lyrid observing. IMO data suggested a prolonged maximum, with ZHRs ~ 20 +/- 10, between the UT evening hours of April 21 through to perhaps midday UT next day, something also seen in the radio reports, with most operators registering a peak in echo counts between April 21d16h UT to April 22d11h UT. The predicted maximum was due between April 21d22h UT to April 22d05h UT.
Eta Aquarids: (See also News Circular 215) Benefitting from May's new Moon, the eta-Aquarids produced an interesting pattern of activity in early May. SPAMS visual data indicated ZHRs of 50-65 +/- 10-20 on the mornings of May 2 and 5-8 inclusive, peaking on May 5-6 at ~ 60-70 +/- 10, about as predicted. The radio results gave generally enhanced echo counts between May 5-10, with the strongest peak on May 8, two days after the visual one, and another peak on May 10 which may have been richer in faint meteors. ZHRs on May 10 were only 25 +/- 5, perhaps showing how many faint eta-Aquarids were being lost in the near-dawn twilight if so. From 143 eta-Aquarids seen in better skies, a corrected mean magnitude of +3.1 was computed, fainter than normal, while the May sporadics' value was +4.0 (187 meteors).
May 6 Meteorite Fall, Czech Republic: (See also News Circular 215 and the letter with three video images by P. Spurny in WGN 28:2/3 (2000 April-June), pp. 44-45. The cover of this issue of WGN has two photos of the main meteorite as well) At 11h51m UT, a shower of stony meteorites fell on the village of Moravka in Silesia, the largest recovered of ~ 214g. Video records mean an orbital analysis will be possible. A second, equally brilliant, fireball flew over the Czech Republic and Austria at 17h15m UT on May 10, but no reports of a meteorite recovery were made afterwards, though a long-lasting dust cloud was left hanging in the air as seen from Hungary (see also News Circular 215 on this event).
June Daytime Radio Shower Activity: May to July generally brings radio observers some of the best meteor activity of the year, all in the daytime sky. Unfortunately, 2000 also brought some of the strongest Sporadic-E interference for many years, and in June and July, radio operators were often barely able to make any useful reports on a lot of days. One highlight during this time was an observation from the Australian SKiYMET meteor radar communication system, which managed to make a radiant determination for one of the strongest daylight radio showers, the Arietids, at RA 3h16m +/- 16m, Dec +28 degrees +/- 2 degrees between June 6-8, a close match for the expected position, last confirmed in the early 1970s, around RA 2h56m, Dec +24 degrees. Similar radars in Brazil, Sweden and Germany confirmed this June 6-8 spell as producing the shower's highest activity, again a useful tie-in with the expected date of June 7. This is especially valuable as another radiant from a strong radio shower, the zeta-Perseids, lies just over an hour in RA east of the Arietid radiant at its maximum on June 9, a proximity in space and time which means typical radio meteor systems have no chance to tell which shower is producing which rates.
June 17-18 Fireball: (See also News Circulars 215 and 217) A magnitude -6/-9 event occurred around 21h10m-21h15m UT in evening twilight, as spotted from six sites in central-southern England and south Wales. Though details were sketchy in most reports, an approximate east to west trajectory is suggested for the fireball, above the northern Midlands around the Derby area.
June Bootids: (See also News Circular 215) Only very weak to nonexistent activity was seen from this source in 2000 in both SPAMS and IMO data, so we must keep waiting and wondering when another outburst event like that in 1998 might happen!
Perseids: For details, see News Circulars 215 & 218, and especially the SPA Meteor Section Report: Perseids 2000 on this Website.
Late August Fireball Spate: For details, see News Circular 215, but especially the detailed discussion listing Late August 2000 Fireball Spate: A Review of Observations Received on this Website.
Orionids: As anticipated, October's waning Moon spoilt the chance for visual watchers to cover the shower's peak, and very few ZHRs could be calculated at all. Usually under such circumstances, we now tend to look to the radio data as a guide to what occurred, but this year the Orionid "bulge" of increased echo count numbers that commonly falls between October 14-25 was rather erratic, almost as if rates might be fluctuating quite markedly from one night to the next fairly randomly. October 20-21 was generally when the strongest meteor echo totals happened in a majority of radio datasets, and there seemed little evidence to support the strong pre-maximum peak around October 17-18 in 2000, which was last seen in 1998, at least. It is possible that a relatively newly-detected type of radio propagation interference noted by ham radio operators (rather than radio meteor observers) was responsible for these curious Orionid results. What this propagation was is unknown, but it has now been found during the last two solar maximum years, and not at other times.
October 19-20 Fireballs: Two brilliant non-Orionid fireballs were reported a couple of hours apart, the first at 19h34m UT as seen from two locations in Lancashire and on the Isle of Man, the second at 21h31m UT spotted by a single observer in Wiltshire. Unfortunately, neither event was well-seen enough to work out where they may have occurred above.
November 3-4 Fireball:
(See also News Circular 217
) Around 19h05m-19h10m UT, a fireball of about magnitude -8 to -10 was witnessed from 19 sites across southern England and the Isle of Wight northwards to the south Wales-England border and eastwards to South Yorkshire and Humberside, as well as at one site in the Netherlands. Unfortunately, the exact track of this object could not be firmly established from the results submitted, but the sketch map of south-east England alongside here shows the most likely general surface path. Black dots show where some of the witnesses were located near the fireball's track. It is likely the fireball passed on a generally ESE to WNW trending track descending from around 90 km to 50 km altitude during its flight, which probably started over the southern North Sea. It crossed the English coast heading inland north of London, passing high above Essex, northern Hertfordshire and Bedfordshire, and ending some way east of Northampton. The object was fragmenting along much of its trail, and produced a very late disintegration into a number of discrete, small, pieces before fading out. Assuming the above estimates to be broadly correct, the visible-flight atmospheric trajectory may have been ~ 180-220 km long, and lasted ~ 5-10 seconds according to the better estimates, implying a probably slow atmospheric velocity of between 20-35 km/s. The path direction and the meteor's speed indicate it is quite likely to have been a Taurid, but this could not be definitely confirmed either. Most observers mentioned seeing a blue-green colour at the fireball's brightest, with yellow a popular description for other parts of the event's trail.
Early December Fireballs: December opened with two single-witness fireballs on 1-2, the first around 20h UT (Perthshire, Scotland; bright), the second at 00h50m UT (Nottinghamshire; magnitude -5, low to the north). Then another four non-shower fireballs were seen by lone observers during the first half of the month from the UK, on December 5-6 (~ 17h45m UT; near Moray Firth), 9-10 (~ 17h55m UT; Northumberland), and 13-14 (~ 19h24m and 19h41m UT; both Northumberland), all between magnitudes -3 to -6. The Northumberland sightings were made by different observers, those on December 13-14 seen by people less than 5 km apart, but without either observer seeing both events!
Geminids: (See also News Circular 217) The Geminid peak was the main radio highlight of December for most such observers, as normal, though there was little close agreement as to an exact maximum time for the shower. Most datasets showed very good echo counts on both December 13 and 14, with the stronger activity on the latter date. The lack of consensus regarding a specific maximum time was not unexpected from recent Geminid returns, with the preliminary IMO visual results suggesting ZHRs of ~ 120-130 +/- 10-20 were seen between circa 20h-03h UT at least on December 13-14. SPAMS European data concur, and show identical ZHRs persisted through until ~ 04h-05h UT then. Unfortunately, the bright waning gibbous Moon apparently deterred a lot of people from observing, but even so it has been possible to construct a magnitude analysis, as illustrated in the graph below, based on details from 239 Geminids and 107 December sporadics. Just under 9% of Geminids left persistent trains this year, compared with 1.6% of sporadics.
(See also News Circular 218
and the article "Possible Ursid Outburst on December 22, 2000" by P. Jenniskens & E. Lyytinen in WGN 28:6
(2000 December), pp. 221-226) Although the UK was clouded-out entirely for the Ursids, judging by comments from unlucky observers, using visual and radio data submitted to the SPAMS from elsewhere and drawing on IMO and Nippon Meteor Society visual results circulated on the IMO-News
e-mailing list within days of the event, a possible double Ursid maximum may have happened on the morning of December 21-22. The first peak was around 05h-06h UT (ZHRs ~ 20 +/- 5), roughly in time to the predicted normal maximum, expected around 06h UT, with a second peak around 08h-09h UT (ZHRs ~ 30 +/- 5). Interestingly, the 1996 radio Ursid peak was found at the same equivalent time as this possible second maximum in 2000. The radio results give support for peaks between roughly 05h-07h UT (strongest) and 08h-11h UT (less clear, but perhaps made up of brighter meteors). A very strong outburst around 07h30m UT, as suggested by Peter Jenniskens and Esko Lyytinen, does not seem to have happened, but a secondary suggestion by them that rates might be enhanced for some 4-5 hours over the peak could account for the extended maxima found in the radio observations particularly. The observed ZHRs were comparable with other recent minor Ursid enhancements, but were not nearly as high as early e-mailed indications implied. A magnitude distribution for the 88 Ursids seen in better skies is given in the graph above with the Geminids and December sporadics. Around 5% of Ursids left persistent trains.
Some comparison monthly sporadic data for the better-observed showers of the year has been given in this Review
as normal, and in the separate Perseid and Leonid Reports
, because the sporadics form an essential calibration for all other meteor activities. Although they can be routinely monitored along with the main showers, it is important we have as much coverage of the sporadic complex during the rest of the year as we can too. This additionally allows coverage of the minor showers, of which at least one or two are active on nearly every night of the year. The magnitude distribution graph given here is based on details from 1190 sporadics seen in better skies (limiting magnitude +5.5 or better, cloud cover < 20%) during 2000. From these a corrected mean magnitude of +3.6 has been derived, with a train population of 3%.
As should be obvious, numerous fireball reports were a notable aspect throughout the year. The fascinating distribution of several apparent "clusters" of these sporadic fireballs should not distract us from the fact that fireballs are typically commoner during the major shower maxima however, and even when many such shower peaks were affected by moonlight in 2000, the most productive fireball nights and sources were still January 3-4 (Quadrantids), August 11-12 (Perseids), November 16-17 and 17-18 (Leonids) and December 13-14 (Geminids). Aside from the fireballs already listed, another 30 reports of meteors of magnitude -3 or brighter were received by the Section during the year, 20 of those on the five shower nights mentioned just above. Advice on what to record on seeing a fireball and other information on them can be found on the Fireball Observing
page of this Website.
A selection of interesting meteoric texts published since our last Annual Review, not already mentioned.
"Expectations for the 2000 Leonids", D. J. Asher & R. H. McNaught, WGN 28:5 (2000 October), pp. 138-143. Detailed predictions for what the Leonids might show in 2000 (an article on possible observing conditions for the better-placed locations also featured in this issue of the IMO's journal).
"Video Observations of the 1999 Leonid Meteor Storm Recorded at Different Locations", J. Rendtel, S. Molau, D. Koschny, S. Evans, O. Okamura & M. Nitschke, WGN 28:5 (2000 October), pp. 150-165. The detection of small-scale changes during the 1999 Leonid storm as recorded by video observers, including a radiant derivation and a magnitude analysis confirming the lack of faint Leonids.
"The 'New' Peak Failed: First Analysis of the 2000 Perseids", R. Arlt & I. Haendel, WGN 28:5 (2000 October), pp. 166-171.
- "SPA Meteor Section Results: November-December 1999", A. McBeath, WGN 28:5 (2000 October), pp. 178-182.
"Proceedings of the International Meteor Conference 1999", R. Arlt (editor), IMO, 2000. Usually published within a year of the annual IMO Conference, these publications are always worth reading. This year, items of especial interest to SPAMS members included a paper on the Leonid dust trail theories by David Asher, and a Taurid radiant and activity analysis from 1988-1998 by Mihaela Triglav and Rainer Arlt, which gave more details on the high Southern Taurid activity at the end of October 1998, and confirmed there are more bright meteors present from the shower in "swarm" years.
Sky & Telescope 100:6 (2000 December) has several short items on meteoric topics, including: "'Space Weathering' Cements Asteroid-Meteorite Link", pp. 24-25 (ideas on how S-type asteroids and chondritic meteorites may still be linked, despite apparent differences); p. 25 has a list of binary asteroids; "Sources of the Asteroid Threat" on p. 32 gives predictions for near-Earth asteroid totals; pp. 31-33 have news from several Near-Earth Object search projects; p. 34 has a brief notice about a new lunar meteorite found in Oman; and finally p. 142 has a rather attractive sporadic meteor photo.
"The Secrets of Stardust", J. Mayo Greenberg, Scientific American 283:6 (2000 December), pp. 46-51. The life of interstellar dust particles, how they end up in comets, and finally of course as meteors.
"Bulletin 16 of the International Leonid Watch: Results of the 2000 Leonid Meteor Shower", R. Arlt & M. Gyssens, WGN 28:6, (2000 December), pp. 195-208. A first global overview of results on the shower, including a useful discussion of condition correction factors in calculating ZHRs.
"Dusty Phenomena in the Solar System", A. Graps & A. Juhasz, Sky & Telescope 101:1 (2001 January), pp. 56-63. A useful, introductory discussion of the Solar System's dusty material, including meteors, the zodiacal light and estimates of typical dust lifetimes.
"Sizzling Skies", H. Williams, New Scientist 169:2272 (2000 January 6), pp. 14-19. A useful, reasonably up-to-date discussion of meteor and auroral electrophonic noises, demonstrating that although these simultaneous sounds are now recognised as being real, we still do not understand why they occur.
"Leonids Surprise and Impress", G. Seronik, Sky & Telescope 101:2 (2001 February), p. 136. Brief notes on the 2000 Leonids, concentrating primarily on personal recollections.
International Meteor Organization
For further information on the IMO, see the Website at: http://www.imo.net
. Anyone seriously interested in meteors or meteor astronomy should consider becoming an IMO member. An application form can be found on the IMO Website, or contact the SPAMS Director. The cost to join in 2001 remains the same as in 1995, 16 GBP (which includes a 2 GBP administrative fee payable only in your first year of membership).
Just room left to thank everyone again who contributed to the Section in 2000, and to wish you all a most successful year's observing in 2001, when many major showers are less troubled by the bright Moon. I look forward to hearing of your efforts and seeing your reports. Good luck, and as always, clear skies!
Prepared by Alastair McBeath, SPA Meteor Section Director.
Added by: Tracie Heywood