The 1990s continue to be an exciting time in meteor astronomy, with 1998 especially spectacular thanks to three amazing meteor outbursts, two of them seen from the UK – and still we have the possibility of a Leonid storm to come in 1999 or 2000! Though the weather during the year was no better than normal – indeed in Britain, most people will recall it as "the year without a summer" – the clearer nights that did come along were beautifully timed to coincide with the most important meteoric events for once. Details on the various events during the year are given below as usual, except for the Leonids, because so many reports came in from them. Instead, we have published a Special Report on the 1998 Leonids, which is available separately.
Grand Totals and Observers
The overall totals for the various observing techniques were: Visual – 1393.9 hours, 27,354 meteors; Photographic – 1384.3 hours, 38 trails (of which 32 have so far been identified; these included 24 Leonids, 7 June BoÃ¶tids and 1 sporadic); Radio – 40,533.9 hours, 1,556,300 meteor echoes. The visual and photographic tallies were notably boosted by data from the German Arbeitskreis Meteore (AKM) observers, details of which were extracted from AKM journal Meteoros kindly provided by Ina Rendtel and one of the AKM’s leading observers JÃ¼rgen Rendtel. Other very active AKM members included Christoph Gerber, Sylvio Lachmann, top observer Sven NÃ¤ther, Harald Seifert and Oliver Wusk. Most of the radio data came from the Radio Meteor Observation Bulletins (RMOBs), which Chris Steyaert in Belgium thoughtfuly submitted to us. Many other correspondents have also helpfully contributed information to the Section during the year, as noted both in the regular SPA News Circulars columns and the SPAMS results articles published in the International Meteor Organization’s (IMO’s) journal WGN. All such contributions are again most gratefully acknowledged here. The list of people providing observational data 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 list contains only the country most observations were made from, and the abbreviations indicate the type of observing carried out. "P" denotes photographic or video, "R" radio, and "V" that visual results were also contributed by that person. Observers without an additional letter provided purely visual observations:
Enric Fraile Algeciras (RMOB, Spain; R), members of the AKM (Germany; P/V), Rainer Arlt (Germany), David Asher (Northern Ireland), Eva Bojurova (Bulgaria), Neil Bone (England), John Bonsor (Scotland), Mike Boschat (RMOB, Canada; R), Keith Bowley (England), Jay Brausch (USA), Giorgio Bressan (RMOB, Italy; R), Eisse Pieter Bus (RMOB, Netherlands; R), Ovidiu Ciorianu (Romania), John Coates (England), Tim Cooper (South Africa), Heather Couper (England), Andrea Csiki (Romania), Maggie Daly (England), John Davies (England), Norman Davis (RMOB, USA; R), Zoltan Deak (Romania; P), Maurice de Meyere (RMOB, Belgium; R), Ade Dimmick (England), Carol Downs (England), Bev Ewen-Smith (Portugal; R/V), Penny Feltham (England), Guy Fennimore (England), Steve Foggo (England), Doug Fox (England), Dave Gavine (Scotland; P/V), Ghent University (RMOB, Belgium; R), Bob Gilmour (Scotland), Shelagh Godwin (England), Peter Grego (England), Valentin Grigore (Romania), Alan Heath (England; R/V), Mark Herbert (USA), Kath Hodges (England), Terry Holmes (England; P/V), Tom Hosking (England), Simon Jenner (England), Ou Yang Tian Jing (RMOB, China; R), Will Kelsey (RMOB, USA; R), Katya Koleva (Bulgaria), Werfried Kuneth (RMOB, Austria; R), John Lambert (England), Marco Langbroek (Netherlands), Anne Lascelles (England), Peter Lascelles (England), Trevor Law (England), Richard Livingstone (Wales), Alan Longstaff (England), Bob Lunsford (USA), Kimio Maegawa (Japan; R), members of Malta AS, Andrew Mark (Scotland), Tony Markham (England), Alastair McBeath (England), Peter McBeath (England; P/V), Tom McEwan (Scotland), Kieron McGrath (England), John Meyer (RMOB, USA; R), Vasile Micu (Romania; P), R B Minton (USA; P/R/V), Jacqueline Mitton (over the Atlantic Ocean), Neil Mortimer (England), Sadao Okamoto (RMOB, Japan; R), Guy Ottewell (USA), members of the Petnica Meteor Observing Group (Yugoslavia), Graham Pointer (England), Edward Polehampton (England), Veselka Radeva (Bulgaria; P), Lyna Rashkova (Bulgaria), Ingo Reimann (RMOB, Germany: R), Ina Rendtel (Germany), J rgen Rendtel (Germany; P/V), Tony Rickwood (England), Ian Rigney (England), Joan Robinson (England), Maurice Robinson (England), Vanya Rodiger (Croatia), Paul Roggemans (Belgium), Andy Salmon (England), Elena Sarbinska (Bulgaria), members of the SARM group (Romania; P/V), Robin Scagell (England), Fred Schaaf (USA), Ton Schoenmaker (RMOB, Netherlands; R), Jonathan Shanklin (over the Atlantic Ocean), Chikara Shimoda (RMOB, Japan; R), Amanda Scott (England), Dierdra Shepherd (Australia), Jamie Shepherd (Australia), Adrian Sonka (Romania; P/V), George Spalding (England), Paul Sutherland (France), Melvyn Taylor (Cyprus), Pierre Terrier (RMOB, France; R), Anda Tita (Romania), David Todd (England), Stanley Toyn (England), Manuela Trenn (Germany), Mihaela Triglav (Slovenia; P/V), Valeriu Tudose (Romania; P/V), James Vanderpool (England), Valentin Velkov (Bulgaria; P/V), Cis Verbeeck (Belgium), Andrew Walker (Scotland), Peter Ward (England), David Weldrake (England), Robert White (England; R), Graham Wolf (New Zealand), Ilkka Yrj l (RMOB, Finland; R), Wim T Zanstra (RMOB, Netherlands; R).
The leading visual observers amassed over 100 hours of watching each during the year, with several others putting in between 30-70 hours (the top British observer carried out over 65 hours, for instance), though the majority struggled to even reach 10-15 hours. As already hinted at, however, a happy observer was one who was lucky with the weather on only one or two critical nights! Many photographers enjoyed success with the Leonids, and seven of the radio observers operated on more than 250 days out of the year.
Highlights of the Year
Quadrantids: (See also News Circulars 203 & 204 and our results article in WGN 26:4 (1998 August), pp.184-188) Although the weather was far from helpful, a reasonable view of the Quadrantids was enjoyed by many watchers. Visual and radio data both showed a fairly flat maximum, with ZHRs varying little from ~110-130 r10 for over two hours on January 3, centred on 17:30 UT. The corrected mean magnitude for the shower was +2.1 (610 meteors), and 17% left persistent trains, compared to the January sporadics’ values of +4.1 (650 meteors) and 7%.
January 24-25 Fireballs: (See also News Circular 202 and our results article in WGN 26:4 (1998 August), pp.184-188) Five minor fireballs, with magnitudes between -3 and -8 were spotted between 19:45 and 02:35 UT on this night, mostly by solitary observers, unfortunately. A minor peak in radio echoes was also seen on the same night, which had not been detected previously, but if this was an unknown shower outburst, the source remains a mystery. Another bright fireball was photographed from Germany and by other European Fireball Network cameras at 19:13 UT on January 25, but despite initial hopes, no meteorite was found as a result.
February’s Zodiacal Light: (See also News Circular 204 and our results article in WGN 26:4 (1998 August), pp.184-188) Vasile Micu in Romania secured some excellent photographs of both the morning and evening zodiacal light on February 22-23 and 26-27 from his wonderfully dark-skied home site. He was especially fortunate in also capturing a meteor on film quite by chance during the evening observation on February 26.
Plotted Virginid Radiants: (See also News Circular 204 and our results article in WGN 26:5 (1998 October), pp.225-227) Mainly through the sustained efforts of Tim Cooper in South Africa, our Virginid meteor plotting project was especially boosted this year. Two previously-found radiants from our first five-year Virginid project in 1988-1992 were given some confirmation, Areas 6 (RA ~13h, Dec ~-10y, in late March to early April) and 9 (RA ~12h30m, Dec +3y, in mid-April). Tim’s data also indicated a possible new weak radiant around RA ~12h05m, Dec +3y as March began. Naturally, we still need many more plotted Virginids to allow our analysis to proceed, so send Shelagh an SAE for your meteor plotting pack if you have not yet done so (this also includes details on our autumnal Aurigid and Taurid plotting project).
March 15 Twilight Fireball: (See also News Circulars 202 & 204 and our results article in WGN 26:5 (1998 October), pp.225-227) Around 19h UT in the evening twilight, a brilliant fireball was seen from numerous places in south-western England, though unfortunately, with mostly cloudy skies, no accurate information on the object’s atmospheric trajectory has been derived. It is likely the meteor was out over the Channel, but its flight may have run roughly parallel to the south-west coast of England, moving south-west to north-east. A second fireball around 19:45 UT was seen by one observer in southern England, and other fireballs were suspected, a matter further confused by the sighting of distress flares from a small boat in difficulties off the Devon coast. Sonic booms from the brightest fireball were reported by several witnesses too.
Lyrids: (See also News Circular 204 and our results article in WGN 26:5 (1998 October), pp.225-227) Visually a disappointment from the UK thanks to poor weather, but elsewhere ZHRs of ~10-15 were reported in the pre-dawn hours of April 22. The radio results suggested a relatively broad maximum for the shower, which was also hinted at in the visual reports, probably centred close to the expected maximum time, ~10-11h UT on April 22. The Lyrids’ corrected mean magnitude was +1.7 (49 meteors), with 6% trained. The April sporadics’ figures were +3.3 (80 meteors) and no trains.
Eta Aquarids: (See also News Circular 205 and our results article in WGN 27:1 (1999 February), pp.73- 76) Well-seen both visually and by radio, the Eta-Aquarids were the chief highlight of May. Though always a difficult target in twilight, near-dawn skies from the UK, places further south in Europe and especially the southern hemisphere get a better look at the shower. Data from such locations showed peak ZHRs of ~50-60 r10 on May 5-6, slightly lower than in 1997. The peak timing is confirmed by radio data. The Eta-Aquarids’ corrected mean magnitude was +3.3 (175 meteors), not dissimilar to the May sporadics’ value of +3.2. Roughly 45% of Eta-Aquarids were trained, compared to 8% of sporadics.
June 11-12 Fireball: (Briefly mentioned in News Circular 205, but note that the reference to Circular 204 is incorrect, as the report on the meteor that should have featured in Circular 204 failed to appear there! See also our results article in WGN 27:1 (1999 February), pp.73-76) Around 23:05 UT on June 11, a very bright meteor was spotted from sites between the south-west coast of England to Liverpool, stretching across to places north and west of London. There are very few usable sightings from which other information could be derived, sadly, but a generally south-west to north-east ground track can be suggested, perhaps running up the south-west peninsula of England towards Oxfordshire.
June Daytime Radio Shower Peaks: (See also our results article in WGN 27:1 (1999 February), pp.73-76) The main daytime radio shower maxima are usually those in June, the Arietids (peak normally circa June 7) and z-Perseids (peak on or about June 9). In most radio results, these two peaks generally blend together somewhat, but there did seem to be a genuine dip in activity between them in 1998. The Arietid maximum may have happened slightly earlier than expected, but this is not clear in the available data.
June BoÃ¶tids: (See also News Circulars 204-206 inclusive; "Surprising Activity of the 1998 June BoÃ¶tids", by JÃ¼ rgen Rendtel, Rainer Arlt and Valentin Velkov in WGN 26:4 (1998 August), pp.165-172 (the most detailed, authoritative, preliminary report); "SPA Meteor Section Preliminary Radio Results: 1998 June BoÃ¶tid Outburst", by Alastair McBeath in WGN 26:4 (1998 August), pp.173-176 (a detailed review of the first radio results on the event); and "New June Meteor Shower?" in Sky & Telescope 96:4 (1998 October), p.22 (brief preliminary notice)) June 27-28 was one of the three really incredible nights of 1998, when the June BoÃ¶tid meteor shower, last detected in 1927, came back to life for a one-night spectacular. Observers from Japan and New Zealand westwards across Asia and Europe to North America were treated to ZHRs of ~100 for virtually the entire night. Radio results, especially those from Japan, confirmed the event very clearly. Even casual sky watchers were amazed to see several meteors in just a few minutes, rates all-but unheard of in late June, and those with clear skies really enjoyed the show. Luckiest of all was the Bulgarian Astroclub Canopus group who had planned a special observing weekend exactly timed to let them see the wholly unexpected BoÃ¶tid outburst. They had a wonderful night, but had problems staying awake the next night, when only the usual June meteor "drizzle" was available! Early reports suggested the radiant had been rather diffuse, but accurate plotting, much of it from the Bulgarian team, plus a good number of BoÃ¶tid photographs, helped show the radiant to have really been quite compact, centred, to within a couple of degrees, on RA 15h20m, Dec +47y. Doubtless the very slow apparent velocity of the BoÃ¶tids was what misled observers initially into thinking the radiant was larger than it actually was. The corrected mean magnitude for the shower was +2.5 (350 meteors), compared to +1.8 for the June sporadics (166 meteors; this parameter is probably too bright owing to the strong twilight hiding many of the fainter sporadics throughout much of the month). Only 8% of the BoÃ¶tids were trained, still better than the sporadic percentage of zero. There is no way to tell when another BoÃ¶tid outburst may appear; we can but hope it will not be another 70 years away – and keep checking the late June skies just in case!
July 10 Fireball: (See also News Circular 205 – note that again the reference for this object to Circular 204 is incorrect, as the report was mislaid from that Circular) Central and western Britain was treated to yet another bright fireball around 23h UT on July 10. Estimates suggest it was between magnitudes -12 and -20 at its brightest, and it probably fragmented along its trail. Details on its flight direction and apparent speed are contradictory in the few eye-witness sightings received, but the most likely ground track probably stretched from the south-west of England or south Wales northwards to end over the Irish Sea near the Isle of Man. Most unusually, it left a persistent train visible for some tens of minutes, which distorted into a "Q", "S" or "Z" shape over time, quite typical of the forms long-duration trains can take. One sighting suggested the train could still be seen 45 minutes later, with several people reporting only the train, not the meteor. Regrettably too few good reports came through to allow us to derive any further details than these.
July 17-18 Outburst?: (See also News Circular 205) Several radio observers recorded an unexpected spike in echo counts around 01-02h UT on July 18. One visual report from the USA suggested rates of 1-2 meteors per minute in the northern circumpolar sky between 01:50-02:15 UT, but so far no other visual data have been forthcoming, and despite extensive enquiries, no definite identifications for what the source of this event might have been have appeared. One theoretical radiant for potential meteors from a near-Earth asteroid (1997 BR) north of the Plough asterism in Ursa Major was suggested, but although scores of such theoretical asteroidal radiants have been proposed, no activity has ever been detected from any of them so far; perhaps this was the first, but at present, the event remains a mystery.
Southern Delta Aquarid & Alpha Capricornid Maxima: (See also News Circular 205) Some useful data were collected on both these near-ecliptic complexes. Visual results showed the Southern d-Aquarids peaked as expected on July 28, when ZHRs reached ~20 r5, while the a-Capricornids were at their best, ZHRs ~8 r3, on July 30, again much as usual. Too few were seen to derive useful magnitude and train details, however.
Perseids: (See also News Circular 205; "Global Analysis of the 1997 Perseids", by Rainer Arlt in WGN 26:2 (1998 April), pp.61-71, a detailed report on the shower in 1997; "First Impressions of the 1998 Perseids", again by Rainer Arlt in WGN 26:5 (1998 October), pp.218-219, a brief report of global observations; and "Perseids by the Light of the Moon", by Gary Seronik in Sky & Telescope 96:6 (1998 Decem- ber), p.133, another brief shower report) Despite some atrocious weather and the presence of the bright Moon in August, observers were still out braving the conditions to report on this, most favourite of the annual meteor showers. Data sent to the Section showed ZHRs no better than ~80 r25 on August 12-13, but IMO data, and radio results submitted to the SPAMS, clearly revealed that both the new primary and older secondary maxima were present again in 1998, at roughly the expected times. IMO ZHRs were ~130-180 r50 for the primary peak and ~80 r10 for the secondary. The Perseids’ corrected mean magnitude, from 125 meteors seen without the Moon in attendance, was +1.2, while the August sporadics’ value was +2.4 (a mere 38 meteors, however).
August 21 Radio Outburst?: Virtually all the active radio operators on August 21-22 recorded a hitherto unnoticed spike in meteor echo counts then. The European results suggested a peak around 03-05h UT on August 21, but they are not especially clear on this point, and one dataset shows a more prominent spike around 09-11h UT on that date. As there are no visual results for comparison, just what the event was is another mystery from 1998.
Draconids: (See also News Circulars 204 & 205 for brief "before" and "after" notes, respectively; "A Surprise October Meteor Shower?", by Joe Rao in Sky & Telescope 96:4 (1998 October), pp.100-105; "Summary of 1998 Draconid Outburst Observations", by Rainer Arlt in WGN 26:6 (1998 December), pp.256-259 – a preliminary global report on the event; and some brief notes on the shower on p.124 of Sky & Telescope 97:2 (1999 February)) As hoped-for in advance, another outburst did occur from this irregular shower on October 8-9, but it happened several hours earlier than previous returns had indicated, and was best-observed visually and by radio from Japan. Peak rates were noted around 13:10 UT on October 8, and were around 720 r90, though this figure may be inflated because of the bright Moon. The activity may well have exceeded that seen in 1985, however, when ZHRs were ~300-500 according to recent re-calculations. The spike in rates was well-seen in the Far Eastern radio data, but was generally negligible in the European results, despite the Draconids’ circumpolar radiant from Europe being high in the sky at ~13:10. In the UK, so many reports were received within days of the event that it was almost possible to draw up a weather map of who had had clearer or cloudier skies on October 8-9! Despite some excellent efforts – several people began observing in what we would usually think of as impossibly strong twilight, when only Vega could be glimpsed overhead – British watchers saw ZHRs no better than 8-10 r3-4 from the Draconids, the very tail-end of the outburst in the 60-90 minutes of darker skies after sunset and before moonrise. No Draconids brighter than magnitude +2 were seen from Europe, and too few were recorded to allow us to derive sensible magnitude or train details. Even so, several observers commented delightedly on seeing even a few, very slow-moving Draconids. Unfortunately, changes to the comet’s orbit mean it will probably be 2018 before another return can be sought, unless something unexpected occurs before then.
- Orionids: A wonderful observing effort was put in by many of our watchers for this shower later in October, and it has been possible to derive a basic mean ZHR graph, with rates condensed into single daily values, as shown below to the right. Another pre-maximum higher ZHR period was detected on October 17-18, similar what was found in 1993. The highest individual ZHRs from SPAMS results were ~27 r10 then, significantly above the normal value of ~8-11. The radio rates also support this increased Orionid activity, especially between 05-07h UT on October 18. The main Orionid maximum was unusually sharply-defined in 1998. Normally, rates show relatively slight variation for 2-3 days over the peak, but both visual and radio data did not indicate such an event for once. The best mean ZHR on October 21-22 was 32 r4, also a little higher than usual (normally ~20-25). The Orionids’ corrected mean magnitude was +2.6 (263.5 meteors) compared to the October sporadics’ +3.5 (578.5 meteors), with 31% of Orionids and 5% of sporadics leaving trains.
Taurids: (See also "Taurid Swarm Appearing in 1998?", by David Asher & Kiyoshi Izumi in WGN 26:5 (1998 October), p.217) Following the above timely warning about possibly enhanced Taurid rates, it does seem that something unusual took place with the Taurids in 1998. Radio rates failed to drop as quickly as normal after the Orionid maximum had passed, and most reports showed a distinct peak in echo counts not previously noticed on October 29-30. When this was compared with the visual results, it seems that the unexpected activity came from the Taurids, as the simplified ZHR graph to the right here indicates. In the graph, both Northern and Southern Taurid rates have been combined into a single figure, per date. These combined ZHRs on October 27-28 and October 30-31 were equivalent to the normal early-mid November maximum rates, ~9-10 r2. The full Moon in early November prevented further accurate visual observations after November 1 until November 15, but the radio data showed no further anomalies during this time at least. In addition, a surprisingly high proportion of Taurids were fireballs seen during late October and into November. Around 7% of the Taurids reported to us were of fireball class, for instance (compare that to just 1.1% of the 1998 Orionids). All of this tends to support the idea that a recurrence of the Taurid "swarm" did happen in 1998, producing more bright meteors and fireballs, as well as abnormally higher rates up to two weeks ahead of the usual maximum. From 81 Taurids, a corrected mean magnitude of +2.5 was derived, with under 3% trained. Our Taurid plotting project continued, but too few plots were made to allow any new details to be derived. One of the leading IMO workers, and also a supporter of the SPAMS, Mihaela Triglav is currently working on an on-going project examining the Taurid and other autumnal meteor shower radiants, and SPAMS meteor plots are also now passed to her to assist her analyses.
Leonids: (See also News Circular 206 for an initial brief report and wonderful photo, and also numerous articles in WGN 27:1 (1999 February) on the 1998 Leonids, with more superb pictures. Also make sure you send for your copy of our Special Leonid Report which has a further host of details and references on the shower) As already noted, we give no additional details here on this, arguably the most incredible of the meteoric events in 1998. This is entirely because our Special Report, which discusses the shower and the observers’ reactions to it, is a separate document the size of this Annual Review!
Geminids: (See also "December’s Generous Geminids", by Joshua Roth in Sky & Telescope 96:6 (1998 December), pp.117-118; "Observers’ Notebook: Geminids Galore", by Gary Seronik in Sky & Telescope 97:4 (1999 March), pp.117-118) Although producing their typically reliable rates in December – as the mean ZHR graph to the left here notes – several observers who were lucky enough to have clear skies for them (excluding most British observers, however) wrote saying the shower had not been a patch on the superb Leonid display of less than a month earlier! This was an unfortunate, but perhaps unsurprising, comparison to draw, as normally, the Geminids leave the Leonids standing, in terms of meteor brightnesses and rates. Highest Geminid activity occurred slightly later than expected on December 13-14, with mean ZHRs for the whole night of ~70 r4, but looking at the subset of data closest to the peak only yielded ZHRs ~110 r15 around 06-08h UT on December 14, confirmed in the European radio data. Very few Geminid fireballs were reported, which is reflected in their somewhat fainter than usual corrected mean magnitude of +2.8 (555 meteors). The December sporadics had a corrected mean magnitude of +3.1, with ~6% of both classes of meteor giving rise to persistent trains.
December 25 Fireball: By contrast to the other widely-seen bright fireballs over the UK in 1998, this object was reported by just two people, at 22:27-22:28 UT. It was probably around magnitude -6 to -8. However, because both observers gave rough positions in the sky where they had seen the meteor, a more accurate probable ground track could be established. This most likely ran from SSW to NNE, probably passing close to, or directly over, Peterborough in Cambridgeshire. Both observers recorded the meteor as blue-white with a fiery red crescent near its head.
As ever, we have given comparison monthly sporadic data for all the better-observed showers of the year as we have gone along, since the sporadics are our essential calibration source 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 as well. Based on results from 2179 sporadics seen during all of 1998, a corrected mean magnitude of +3.5 has been derived, with a train population of 6%.
An astounding 408 fireball reports were received by the Section, 328 of those on November 16-17! Thanks to the very large number of Leonid fireballs on that one night, and their proximity in time to one another, it has not been possible to accurately estimate how many of these fireball reports were of the same event seen from different sites. It is likely that quite a number of the Leonids were seen from several places, but no positional data is available on all but a tiny minority of them, thanks to the incessant fireball "rain". Aside from the fireballs already detailed as definitely sighted from more than one location, one other, a magnitude -3/-4 Perseid at around 21:55 UT on August 12, was probably spotted from two sites in southern England.
The Radio Meteor Year
To continue the radio coverage of meteor activity begun in earlier Section Reviews and Reports, we present a pair of graphs showing the overall daily echo-count tallies from the observers at Ghent University, who operate their radio system 24-hours a day whenever possible. The few gaps in their data, chiefly caused by problems with the Sporadic-E propagation mode during the summer months, have been filled by extrapolation from dates to either side in these. These graphs can also be used to illustrate some of the items found under our "Highlights" section above.
The first graph (to the left) is useful for showing the peaks in echo counts caused by the major showers – especially the Quadrantids, h-Aquarids, daytime Arietids and z-Perseids, the June BoÃ¶tid outburst, Southern d-Aquarids (which are a surprisingly strong radio meteor source), Perseids, Orionids/Taurids, Leonids (very clearly the radio event of the year!), and the Geminids.
The second graph, sets an upper cut-off point that removes the excesses of the two most active major showers – Perseids and Leonids – allowing us to concentrate on the smaller peaks present on various dates throughout the year. We can see in this the less active peaks, such as the Lyrids and daytime b-Taurids (right at the end of June and into early July), and the Ursids in late December. However, there are many other minor maxima during the year too. These are not random fluctuations, as analyses of data submitted to the SPAMS in recent years has shown.
Many of them repeat from year to year at about the same time, showing them to be genuinely due to meteor activity, not instrumental effects in the equipment being used. In addition, many of the peaks can be confirmed by all or most of the radio operators working independently to collect their data. A set of findings from these results was presented by the Director to the 1998 International Meteor Conference in StarÃ¡ LesnÃ¡, Slovakia, and will be published in the Conference Proceedings later in 1999. All of which makes this a very opportune moment to hand over to our Assistant Director for her personal recollections of the 1998 IMC.
The International Meteor Conference at StarÃ¡ LesnÃ¡ – by Shelagh Godwin
In the picturesque setting of StarÃ¡ LesnÃ¡, in the High Tatra mountains of Slovakia, the 1998 IMC was held from August 20th to 23rd. The timing meant that many delegates to the preceding IAU Meteoroids Conference, including several professionals, were able to attend the IMC. These professionals, particularly Dr Colin Keay, were appreciative of the IMO’s efforts over the years in bringing amateurs and professionals together: this kind of co-operation seems to be particularly evident in Japan. The 65 delegates attending the IMC included people from Japan, Canada, the USA and the Canary Islands as well as from several European countries. The choice of Slovakia was appropriate in view of the great contribution made by Slovak scientists to meteor astronomy. It was there that the 1946 Draconid storm was observed and, during an interesting discussion between the amateurs and professionals present, Dr Zdenek Ceplecha, who had seen the outburst, was able to tell us what it was like.
The conference proper started on the Friday morning, but on the Thursday evening we were treated to slide presentations of an astro-camp held in Slovenia (presented by Mihaela and Gabrijela Triglav), and some stunning pictures from Bulgaria, (presented by Valentin Velkov and Eva Bojurova).
Work on observing meteors proceeds apace, with the use of video, radio, photographic and radar, as well as visual, methods. But with the unexpected 1998 outburst of the June BoÃ¶tids and the hoped for storms from the Draconids and Leonids, attention was focussed on the visual element. For instance, for the BoÃ¶tid outburst, the Bulgarians and the Romanians were extremely fortunate in having clear skies. We were urged to keep watch every night, and always to plot what we saw. There could be another outburst next year. Rainer Arlt gave a useful outline of the history of the shower. As for the Draconids, they could be affected by bright moonlight, but Alastair McBeath urged us to get out and observe. The Leonid shower was likely to be best seen from the Far East: the IMO was planning a trip to Mongolia to see it, with JÃ¼rgen Rendtel and Peter Brown as leaders, and the Dutch Meteor Society was planning to go to China. However the shower would also be worth looking out for from European sites. Indeed the Slovakian observers have been on the lookout for the past few years now. Peter Jenniskens, who had been seconded to NASA and was involved in a NASA plan to send a plane up to observe the Leonid shower, had much to say on the subject. Peter Brown from Canada spoke of the effect on the meteor stream of planetary perturbations particularly from Jupiter and Saturn. He said it would be useful during the Leonid shower to watch out for meteorite impacts on the moon, for electrophonic fireballs, however unlikely these might be, and what he and Peter Jenniskens both described as the heliocentric radiant glow evident before and during a storm (if one occurred). JÃ¼rgen Rendtel and Peter Brown presented a useful survey of visual Geminid observations between 1988 and 1997: this revealed an unusual consistency in the shower profile, with a sharp decline after the maximum and then a plateau some four hours after it. I believe there were very few participants at the conference who had not contributed to the survey by making visual observations of the Geminids during at least one of the years concerned. About another shower, less spectacular in numbers but capable of producing plenty of fireballs, Mihaela Triglav said that many more observations of the Taurids should be made if she was to progress with her work on determining their radiants. However, assuming he owns a computer, and has had the necessary training, any visual observer would find the VISDAT database system, demonstrated by Mirko Nitschke, very useful for recording meteors and assigning them automatically to specific showers.
Video work has made spectacular progress in the last few years. The problem with an automatic system is whether to make it so sensitive that it detects everything, or to make it less sensitive and run the risk of it missing real meteors. Chris Trayner spoke lucidly on the subject, but emphasised that the decision on sensitivity must rest with the astronomers. Did they want more results, or less work? According to Mark de Lignie, minor streams had already been detected by double station video cameras. But very precise criteria had to be used in determining whether a stream was sporadic or a new shower. Sirko Molau outlined the history of video observation before introducing his METREC system which is available as shareware. Andre Knofel and Detlef Koschny had made a visual analysis of their Perseid video data: this had revealed problems with colour when observing faint objects and highlighted the need to compare video data with that obtained visually, telescopically, and from radar. Their comparison with radar data, the fascinating subject of a paper presented at the 1996 IMC, was not yet complete. Alastair McBeath, in making a detailed comparison between forward scatter radio and visual data was pleasantly surprised to find a striking similarity between them. However, there is a problem in that we would not expect the forward scatter radio rates to equal the visual ones. So the similarity is both pleasing and worrying: the confirmation of the detected rates is good, the fact that there should be more radio meteors or a different distribution is less so. Work continues. The main problem was deciding the proportion between sporadic and shower meteors, particularly during a major shower peak.
The skies cleared nicely on the Saturday afternoon for the excursion, half way up the highest mountain in the region, to view the Skalnate Pleso observatory and its fine refractor, also the weather station. The same evening we were treated to vivid illustrated accounts of the Czech and Slovak summer observing camps, and a hilarious entertainment presented by the Romanians Valentin Grigore and Andrei Gheorghe, consisting of astro-poetry, singing and dancing, and taped `space music’. As evidenced by their papers on the Sunday morning, the Romanians see meteor observing as more than a science, they concentrate also on the cultural and spiritual aspects of meteor observing by encouraging everyone from schoolchildren to professors to contribute astro-poetry which is then published. In the last five years they seem to have got the whole country involved in their 3-week "Perseide" event. Limited finances mean a lack, so far, of collaboration between professionals and amateurs. However, with the track of the total solar eclipse on August 11th 1999 reaching its maximum over Romania, things could improve for Romanian meteor astronomy.
It was on this upbeat note that this very stimulating conference ended, with thanks from Alastair McBeath the Vice-President of the IMO, to the indefatigable organisers, Peter Zimnikoval and his wife Beata, and Daniel Ocean!s, and to all those who attended. The 1999 conference will be held near Rome from September 23rd to 26th (well clear of the solar eclipse, the Draconids and the Leonids). I can certainly recommend joining the IMO and considering attending these conferences, particularly if like me you find your efforts frustrated by less than ideal conditions and need to be spurred into doing more observing.
International Meteor Organization News
On the tenth anniversary of its foundation in 1988, IMO work has continued unabated this year, with new, very detailed analyses of major showers including the Perseids, Leonids, Draconids and June BoÃ¶tids being published. Indeed, a poster paper was given by the IMO team at the IAU Commission 22 (Meteors) "Meteoroids" Conference in Slovakia, held just before the IMC, on the BoÃ¶tids, which was generally accorded high praise by the participants. It was interesting too to note how many papers, both presented by IMO officials and others, used IMO data at this professional science conference, something that before the IMO’s conception would have been unthinkable. This shows as clearly as anything what the IMO and its members have achieved in just a decade.
The highest praise was heaped on the Organization by Jack Baggaley, President of IAU Commission 22, and numerous other scientists, many of whom also attended the IMC, as Shelagh has mentioned. It seems that the terms "professional" and "amateur" are no longer applicable to the most knowledgeable meteor scientists and enthusiasts, since the ability and knowledge of part of the so-called "amateur" community is now at least the equivalent of the so-called "professional" one, with the general consensus being that these divisive terms should no longer be used in high-level meteor work by whichever community, paid or unpaid. This praise extends to SPAMS observers, since all SPAMS meteor watch and fireball data is passed to the appropriate IMO Commissions annually for permanent preservation, present and future use. This ensures our results do not vanish into some data-collecting "black hole", never to be used for analyses, and where they could serve no more useful purpose than if they had never been made!
All this is not an indication to rest on our laurels, though, since much remains to be done. The main emphasis for the next few years will be on the collection and analysis of as much Leonid data as possible, so we can present current and future generations of meteor scientists and enthusiasts with the most detailed global overview of the shower ever. Other showers must not be neglected, of course, including unexpected outbursts, or potential activity from the June Lyrid shower, in case it has started to recur. For details on the IMO, its work, and the latest news on matters meteoric throughout the year, see the IMO’s Website
A selection of interesting meteoric texts published since our last Annual Review, and not already mentioned, including our results articles from WGN which covered the latter parts of 1997.
- "The Makings of Meteor Astronomy, Part XVI: W. F. Denning – In Quest of Meteors", M.Beech, WGN, 26:2 (1998 April), pp.85-92. Second in a three-part series on the great British observational meteor astronomer William Frederick Denning, published in 1998 to celebrate his 150th birth-anniversary.
- "SPA Meteor Section Results: July-August 1997", A. McBeath, WGN, 26:2 (1998 April), pp.97-102.
- "On the Impact vs. GMC Model of the K/T Boundary Event", S. Yabushita & A. J. Allen, Astronomy & Geophysics, 39:3 (1998 June), pp.3.28-3.29. Discussions over the Cretaceous-Tertiary boundary event continue, here with comments favouring a cometary impact, rather than an asteroid or volcanism.
- "SPA Meteor Section Results: September-October 1997", A. McBeath, WGN, 26:3 (1998 June), pp.139-142.
- "SPA Meteor Section Results: November-December 1997", A. McBeath, WGN, 26:3 (1998 June), pp.143-146.
- "The Day the Sands Caught Fire", J. C. Wynn & E. M. Shoemaker, Scientific American, 279:5 (1998 November), pp.36-43. An expedition to the Wabar Craters in the Empty Quarter of Saudi Arabia, created by a series of sand-impacts which happened at some point between 6400 years ago and 1891!
- "The Search for Greenland’s Mysterious Meteor", W. W. Gibbs, Scientific American, 279:5 (1998 November), pp.44-51. An article detailing the fruitless search for the supposed Greenland "meteorite" of 1997 December 9. The article points out just how vague some of the details on this event really were.
- "Meteorites: Flux with Time and Impact Effects", edited by M. M. Grady, R. Hutchison, G. J. H. McCall & D. A. Rothery, published by the Geological Society, London, 1998. This book contains a series of 18, at times highly technical, papers by the leading experts in the fields of meteoritics and meteorite impact science. It is an excellent review of the state of research in this area, including what we do and don’t know, with further discussions about mass-extinction events in the geological record from the biological perspective – yes, the K/T boundary event is fully discussed too! For those with a serious interest in keeping up-to-date on these topics, an invaluable text.
- "Meteors That Changed the World", B. E. Schaefer, Sky & Telescope, 96:6 (1998 December), pp.68-75. A discussion of meteorite worship and physical impact effects. Note the comments in it about the K/T boundary mass extinctions now being fully understood are very misleading. As item 8 above shows, there is still much debate about even what the evidence from the boundary geology really means.
- "Saga of the Lump: The Pallas Meteorite", R. E. Gallant, Sky & Telescope, 97:1 (1999 January), pp.50- 54. Concerning the re-finding of the Pallas meteorite in Russia, its history and its effects on meteorite science.
- "The Makings of Meteor Astronomy, Part XVII: W. F. Denning and Comets, Nebulae and Novae", M. Beech, WGN, 26:6 (1998 December), pp.268-272. The concluding part of Martin Beech’s Denning anniversary biography.
- "Investigating Near-Earth Asteroids", A. Harris & J. Davies, Astronomy & Geophysics, 40:1 (1999 February), pp.1.10-1.13. This paper includes details of a new investigation of asteroid 3200 Phaethon (possibly the Geminid meteor shower’s parent body) suggesting its surface is solid rock. The piece argues against the object being an extinct comet on this basis.
- "New Limiting Magnitude Tables", R. Arlt, WGN, 27:1 (1999 February), pp.6-18. An excellently revised and improved series of charts for using the area-count limiting magnitude determination method.
- "Microbes in a Martian Meteorite", A. Treiman, Sky & Telescope, 97:4 (1999 April), pp.52-58. The latest findings from ALH 84001, but the evidence for life remains open to question.
Scarcely room left to wish you all a successful year’s observing, and good luck especially for "the" eclipse in August and the Leonids on 1999 November 16-17 and 17-18. Many thanks too to those who have sent cards and good wishes during my currently on-going illness. Clear skies!
Alastair McBeath, 1999 April 28
Director: Alastair McBeath, (Observations and advice on all aspects of meteor work).
Assistant Director: Shelagh Godwin, (New Section members and Section publications).