THE ’S TALE Newsletter of the Comet Section of the British Astronomical Association

Volume 4, No 1 (Issue 7), 1997 May

COMET OF THE CENTURY ?

From a colour print by Mike Cook, Romford. 1997 March 29. 50-mm lens, 10 mins, Kodak Panther 1600

BAA COMET SECTION NEWSLETTER ii THE COMET’S TALE

Comet Section contacts

Director: Jonathan Shanklin, 11 City Road, CAMBRIDGE. CB1 1DP, England. Phone: (+44) (0)1223 571250 (H) or (+44) (0)1223 251400 (W) Fax: (+44) (0)1223 362616 (W) E-Mail: JDS @ AST.CAM.AC.UK or J.SHANKLIN @ BAS.AC.UK WWW page : http://www.ast.cam.ac.uk/~jds/

Assistant Director (Observations): Guy Hurst, 16 Westminster Close, Kempshott Rise, BASINGSTOKE, Hampshire. (and also Editor of RG22 4PP, England. The Astronomer magazine) Phone & Fax: (+44) (0)1256 471074 E-Mail: GUY @ TAHQ.DEMON.CO.UK or GMH @ AST.STAR.RL.AC.UK

Assistant Director: James Lancashire, Flat 4, 14/16 Canynge Road, Clifton, BRISTOL. BS8 3JX, England. (Urgent correspondence) Phone: (+44) (0)117 973 9963 E-Mail: JALAN @ AST.CAM.AC.UK

CCD Advisor: Nick James, 11 Tavistock Road, CHELMSFORD, Essex. CM1 5JL, England. Phone: (+44) (0)1245 354366 E-mail: NDJ @ ASTRO1.DEMON.CO.UK or NICK.JAMES @ GMRC.GECM.COM

Photographic Advisor: Michael Hendrie, Overbury, 33 Lexden Road, West Bergholt, COLCHESTER, Essex, CO6 3BX, England Phone: (+44) (0)1206 240021

Section news from the Director

Dear Section member, reported in astronomical Stephen Laurie, Ron Livesey, magazines over the coming John Mackey, Glyn Marsh, Nick Needless to say I have been months. Martin, John McConnel, Hazel overwhelmed with observations McGee, Richard McKim, Haldun of comet Hale-Bopp! Despite The Keedy award for 1996 has Menali, Martin Mobberley, going through the details for been awarded to Gabriel Oksa of Stewart Moore, Bob Neville, reporting observations at the Starohajska, Slovakia. Gabriel Detlev Niechoy, Brian section meeting last year, has been studying at O'Halloran, Gabriel Oksa, Roy observers are still making Loughborough University on a Panther, Terry Platt, Tony mistakes in reporting their Royal Society post-doctoral Rickwood, John Rogers, Jonathan observations. This greatly fellowship, but has now returned Shanklin, Don Shirreff, James increases the workload for Guy home. He started observing Smith, John Smith, Peter Stanley, and myself as we have to correct for the Section in March Enrico Stomeo, David Storey, or replace the observations at a 1996 with the appearance of David Strange, Tony Tanti, later date. Some of the problems , and has quickly Christopher Taylor, Melvyn are listed in the observing section. developed into an experienced Taylor, Alex Vincent, Greme observer. Waddington, Richard Walters, Comet Hale-Bopp has certainly Peter Ward, James Weightman, been one of the most intensively Since the last newsletter Paul Yates, Joe Young and the observed comets in history and observations or contributions Mid Kent AS. section members have made the have been received from the following BAA members: most of the opportunity. I’ve Contents included a few of the many images received in the newsletter James Abott, Sally Beaumont, and more will be on display at the John Bingham, Graham Boots, Comet Section contacts 2 exhibition meeting. The Denis Buczynski, Robert Bullen, Section news 2 Astronomer magazine hopes to Peter Craven, Clive Curtis, Eric RAS meeting 3 bring out a supplement in the Dinham, Jean Dragesco, Len Spectroscopy 4 autumn which will document the Entwisle, John Fletcher, James comet’s apparition and at some Fraser, Mike Gainsford, Steven Fried comets ? 6 stage in the future a BAA Memoir Goldsmith, Massimo Giuntoli, Letters 6 will also appear. I haven’t David Graham, Werner Hasubick, Tales from the Past 7 documented the results of Michael Hendrie, Colin Henshaw, Review of observations 8 professional observations in great Guy Hurst, Nick James, Norman detail here as they will be Kiernan, James Lancashire, BAA COMET SECTION NEWSLETTER 1997 MAY 3 and also from: Jose Aguiar, classifications). Thanks to all of issue, section web page, or BAA Cornel Apetroaei, Alexandr you for your contributions. newsletter. Baransky, Sandro Baroni, John Bortle, Reinder Bouma, Mike Comets under observation were: Some BAA membership Cook, Tim Cooper, Matyas 22P/Kopff, 29P/Schwassmann- milestones reached over the past Csukas, Alfons Diepvens, Wachmann 1, 46P/Wirtanen, year include the Director (25 Maurizio Eltri, Stephen Getliffe, 81P/Wild 2, 118P/Shoemaker- years), David Frydman, Mike Guus Gilein, Bjoern Granslo, Levy 4, C/Hale-Bopp (1995 O1), Gainsford and Richard Miles (30 Roberto Haver, Lars Heen, C/Tabur (1996 Q1), years), Philip Vince (40 years) Andreas Kammerer, Heinz C/Hergenrother-Spahr (1996 R1) and Roy Panther (50 years). Kerner, Atilla Kosa-Kiss, Martin and C/Mueller (1997 D1). Congratulations to all. Lehky, Dee Levers, Romualdo Lourencon, Herman Mikuz, Some of the best material Finally if you do have any Antonio Milani, Sue Morley, John showing Hale-Bopp will be on comments on the newsletter, or O’Neill, Robert Oseman, Rok display at the Exhibition Meeting, requests for topics to be covered Palcic, Amanda Peters, Ernie so do come along and view it. I at the Section meeting do let me Richardson, Josep Rodriguez, hope to organise a section know. Clear skies, Virgil Scurtu, Oddleiv Skilbrei, meeting in Cambridge during the Steinar Thorvaldsen, Alin Tolea, autumn, but this will depend on Jonathan Shanklin John Vetterlein, Seiichi Yoshida there being a breather from bright and Vittorio Zanotta (apologies comets! More details in the next for any omissions or miss-

RAS Discussion Meeting on “Comet- Connections”

The media have an interest in of dormant comets as they would dead HTC (between 3000 and bombardment from space at the be embedded in a 12,000). moment, but having watched stream and would soon be “Asteroid” on TV recently it is reactivated by collisions. Fabio Migliorini (Armagh) fairly clear that they don't have presented results of his study on much idea about what an asteroid Nathan Harris (Armagh) “Resonant Delivery of is, or the links between asteroids disagreed with this in his paper on and from the Main and comets. This meeting was “Inactive Comets Among the Belt” which is part of a European organised by Mark Bailey of Near-Earth Asteroids”. Plotting Community funded GAPTEC Armagh Observatory and Iwan the aphelion distance Q against project to investigate the NEO Williams of Queen Mary College, the perihelion distance q, allows impact hazard. This project has to London and was held at various groups of small bodies, be multinational in order to win Burlington House on March 14. such as main belt asteroids (MB), EC funding and will use ESO I’m not sure that the media would asteroids, family telescopes etc. He showed many have been much wiser after the comets (JFC) and near-earth viewgraphs (often in far too small meeting, and although one or two objects (NEO) to be print) of simulations of resonant new ideas were presented, most distinguished. NEOs have q less scattering into earth crossing talks were repeats of presentations than 1.4 AU and most JFCs have orbits. Most end up in the at the ACM meeting last summer. Q greater than 4.2 AU. The after a few million years. He NEOs can be split into class 1 suggested that the cosmic ray ages David Hughes (Sheffield) kicked with Q greater than 4.2 AU (and of meteorites didn’t reflect off proceedings with a review of thus affected by Jupiter) and class transport time since the parent the ‘zoo’ of small solar system 2 with Q less than 4.2 AU. collision, but possibly the time bodies in a talk entitled Computer models suggest that it since the ‘grandfather’s’ collision. “Distinguishing between Comets is possible to produce JFCs from and Asteroids”. When the both the (OC) and the Neil McBride (Kent) spoke about cumulative number of bodies (KB), but Halley type “: the Debris of larger than a certain size is plotted comets (HTC) only from the OC. Comets and Asteroids”. against the size, the slope of the They also suggest it is impossible Meteoroids can be observed from line is different for asteroids (~-2) to populate the class 2 region, the ground as meteors and as and comets (~-1.67). Several unless non-gravitational forces are impacts on spacecraft. We have a asteroidal families were formed included. Comets in this class good idea of the mass distribution by the collisional break-up of a include 2P/Encke, 111P/Helin- in the mean isotropic flux. parent; in the case of the Eos Roman-Crockett, 82P/Gehrels 3 However meteoroids also occur in family this would be around 300 and 107P/Wilson-Harrington, streams. The flux from these can km in diameter. Most asteroids which are all in some sense be calculated and it works out an were solid, and consisted of ‘strange’. The current population order of magnitude less than the several types, although a few of JFCs can be explained with an overall flux, which can be split might be re-aggregates after injection rate of about one per into helion/anthelion. north/south collisions. By contrast comets century and a dynamical lifetime toroidal and north/south apex were formed by accretion and for class 1 objects of around components. The Taurids do were low density irregular 10,000 years and 1500 years for contribute a significant amount to objects. He pointed out that there class 2 objects. He would expect the anthelion flux. Meteor radars seemed to be no small comets. around 100 dead JFCs to be still give a velocity distribution, but in He didn’t think much of the idea hanging around, but many more the past have missed a lot of fast BAA COMET SECTION NEWSLETTER 4 THE COMET’S TALE meteors (~60 kms-1). He suggests Simon Green (Kent) resumed another field with negative that the apex (fast) source is after lunch, on the topic of results. cometary as is the anthelion. The “Centaurs”. Only seven of these toroidal component probably is strange bodies are known: Chiron, Vacheslav Emel’yanenko (but there isn’t much of it Pholus and five others which orbit (Chelyabinsk) looked at the anyway). The helion source is between Neptune and Jupiter. possibility of “Asteroids from slow and probably asteroidal in They might originate as Trojans, Long-Period Comets”. New origin. Overall more than 60% of but more likely come from the comets are often subject to strong the flux could be cometary. KB. Their size is much larger fading post perihelion. than typical short period comets Mathematical simulations suggest The final talk before lunch was by (SPC) at around 200 km. Chiron that there should be around 4000 Hans Rickman (Uppsala) who has a relatively high albedo of HTC compared to the 20 observed spoke about “Physical and 14%, but the others are more if there lifetime is around 200 Dynamical Interrelationships and typically 4%. There are probably revolutions. Asteroid 5335 Transition Objects”. He first ~5000 within detectable range Damocles, which shows no looked at the formation region with several hundred larger than cometary activity, has a perihelion and growth mechanism of comets 100 km. Chiron shows cometary distance of around 1 AU and has and asteroids. Comets formed far activity and the rotational light probably made around 600 out in the solar system and are curve shows features which point revolutions. He suggested that fragile, low density objects. The to either non sphericity or albedo large nuclei with radius greater Trojan region could be a potential variation across the surface. As than 5 km might be preferentially reservoir of objects. Icy crust the brightens the amplitude deactivated. formation on comets is a rapid, of the curve decreases. Only a common process which may turn small fraction of the surface is Concluding the meeting Alan comets into apparent asteroids. active. Surprisingly the absolute Fitzsimmons (Queen’s University, Occasional collisions in the magnitude is brightest at aphelion. Belfast) summarised observations may temporarily turn According to HST measurements of “Comet Hale-Bopp”. The asteroids into comets and produce still under debate the density is apparent standstill in the light dust bands. Because these events less than one. Pholus is very red curve last autumn could be are rare there are likely to be few and the reflectance spectrum explained if the large dust output examples at any one time. There (which is similar to that of KB gave rise to a strong phase effect. is a relative lack of old long objects) is a good match to Careful selection of the period comets (LPC) with respect tholins. They could be made by observations gave a good straight to new ones, implying that fading cosmic ray bombardment of line fit over the entire apparition exists and a comet is mantled cometary ices. The question of to date, implying no outbursts or within about 10 revolutions. what makes Chiron active and variations in behaviour. Similar There is also a lack of old LPC Pholus inactive and if they are molecules to those seen in 1996 with large perihelion distance SPCs remains unresolved. B2 had been seen and new implying inactivation. There are detections included SO, HCO+ no HTC with q larger than 1.5 Iwan Williams (Queen Mary) and HCCCN. The isotope ratios AU. There are a number of moved a bit further out to talk on of 12C/13C, 14N/15N and 32S/34S are asteroidal objects with cometary “Edgeworth-Kuiper Belt very similar to those of the Earth orbits: Don Quixote (JFC), Objects”. KBOs are near the suggesting that it formed in the Damocles (HTC), 1996 PW limits of detection at a distance of same solar nebula that we did. (LPC, P ~5000 years, q 2.5). Its 50 AU with a size of 100 km. Measurements of the rotation possible to decouple the JFC from There are not enough routine period gave results ranging from Jupiter by a combination of close astrometric observations being 12 hours to one year. The one encounters with the Earth and made (because these are not year period was based on the fact Venus and secular resonances exciting) and once discovered that there was no apparent (which gives evolutionary links many are lost; even observations rotation of the jets over 13 days, between MB and JFC). We don’t over 6 months are equivalent to however these images did show however know what fraction of only one point on the orbit. shells of material being emitted comets, dead comets and asteroids Observational selection is a one the image from one day was form the transition NEOs. He problem because searches are subtracted from an image on the also drew attention to the fact that only carried out near the ecliptic previous day. In a recent INT there are no comets with H0 (because that is where they are image 6 dust shells were visible fainter than about 12. Fainter expected to be seen) and away and these implied a 12 hour comets might be missed or from the milky way. rotation, however the lack of mistaken for asteroids, Unfortunately this currently rotation of the jets couldn’t be alternatively small objects might excludes searches near the explained. The latest telescope on erode very quickly once smaller location of Neptune so the La Palma is a 50mm camera lens than 1 km, especially if this is absence of objects here is not attached to a cooled 2000 pixel combined with fragmentation. He surprising. There may be two CCD camera installed on the INT concluded by pointing out that classes - Pluto types and the rest. roof which had been specially comet 46P/Wirtanen is just such Following the reported detection made to follow the evolution of an object and is a target for the of many KBOs in an HST field, the gas and dust tails. ESA Rosetta mission. Anita Cochran has imaged Jonathan Shanklin

BAA COMET SECTION NEWSLETTER 1997 MAY 5

Low-tech spectrometry: A suggestion for observations of bright near- solar comets.

Christopher Taylor

Most observers, I imagine, would taken by the image, drifting at this method is that one looks straight welcome the chance to use their rate, to pass over the interval into the eyepiece, at a normal telescopes for new types of between the two 1st-order spectra. telescopic view with full observation that reveal interesting The latter must, therefore, be unrestricted field uncluttered by phenomena not accessible to aligned fairly carefully 'fore and additional optics - there is, for simple direct imaging. It is aft' to the preceeding-following instance, no awkwardness of perhaps surprising then, that there directions in the field. One great keeping a narrow spectroscopic is such a possibility which is very advantage of a nylon curtain as slit on target. little used despite the fact that it dispersing element is that we can requires only a telescope on a determine the grating constant D At most declinations the transit simple altazimuth stand, a by actually counting the time Dt generally ranges from 50 stopclock and a few minutes individual threads as stated above, to 80 seconds, so it only takes a preparation time. There is no and this determination of few minutes to repeat the timing need for an equatorial mount, a wavelength is therefore, an in order to improve accuracy by drive, photography, a CCD, absolute one requiring no use of averaging: I generally take sets of computer or any investment in comparison spectra or four to six measures. The single ancillary instrumentation. interpolation formulae. most important procedural point Pretentiously it could be called is to ensure that the axis of "zero-technology objective- The nylon used should have a dispersion (see diagram) is square grating spectrometer"(!). reasonably uniform mesh, without to the register mark and that the superimposed patterns and should latter is square to the p.-f. Take a piece of plain, unpatterned be stretched flat over and fixed to direction (i.e. N.-S.), both to nylon gauze curtain such as is to a rigid diaphragm which is placed within a tolerance of say ±3°. be seen in suburban front over the entrance aperture of the The second pair of 1st order windows, preferably with a mesh telescope in such a way as to be spectra will be found very useful as fine as 1/3 mm and stretch it freely rotatable about the optical in making the first of these flat over the main aperture of the axis. The results below were adjustments (assuming that the telescope, being careful to keep obtained with one of 250 mm 'mesh' of your nylon is truly the threads as straight as possible. clear aperture, having 894±2 rectangular); an offset here will The result, as is well known1, is a threads, hence D = cause a systematic negative bias crude and rather inefficient means 0.2880±0.0006 mm (±0.3%). in the results, while an offset of of producing spectra of celestial The transit timings Dt were made the p.-f. direction will have the objects. What appears to be much with an electronic darkroom opposite effect. Neither of these less well known is that such a stopwatch by watching the two systematic errors is significant if primitive device can actually be opposite 1st order spectra proceed the offsets are at the 2°.level but used for quantitative in tandem across a register mark start to become serious at about spectrometry. It is possible to in the centre of the field; on 4°. Undoubtedly a rather thick make absolute measurements of bringing the object into view and and accurately square pair of the wavelengths in emission line rotating both the grating and the cross-wires in the focal plane sources such as planetary nebulae register mark appropriately, one would be a great advantage here and the heads of near solar obtains an arrangement of 0th but my trials of the method used comets. All that is necessary is a order and four 1st order images nothing more than a matchstick measurement of the diffraction which should be thus:- glued across the field stop of the angle q, an absolute count of the eyepiece! Other sources of threads in the gauze to establish systematic bias to watch out for, their precise mean spacing D, and which will not be apparent in the a simple application of the grating random scatter of the Dt measures formula: themselves, include inaccurate clock rate, wrong D-value (error nl = D sin (q) likely to be ±0.3%), systematic over estimation of Dt due to the Essentially, the theory of the angular diameter of the source method is this: the 1st-order (n=1) (likely to be 0 - 1%) and finally q-value is of order 5-6 arcmin., the dq rate may need correction for which the grating formula may for the object's own proper be approximated to better than 1 motion in the case of a very fast in 106 by l = Dq (q in radians). D It follows that the true field of the moving comet. is determined from the aperture of eyepiece must be at least 4q, the grating and a direct count of preferably rather more, but one The miracle is that such an the threads using a strong should use the highest power that absurdly crude 'grating' is at all magnifier. q is obtained as q = gives this - a typical comet capable of giving spectra of 0.5 dq.Dt, where dq = 7.2921 x eyepiece giving 30 - 35 arcmin. at sufficient purity for any 10-5 cosd sec-1 is the diurnal rate x100 is ideal. It is obvious that meaningful measurements. I have at declination d and Dt is the time another huge advantage of this recently put this to the test by BAA COMET SECTION NEWSLETTER 6 THE COMET’S TALE using some bright planetary always yield the same cometary bands is the dominant nebulae as 'standard sources', all wavelength, but near solar comets emission and with a really bright having visual spectra completely are much more interesting, being comet - Hale-Bopp in April and dominated by the [OIII] emission, essentially dynamic phenomena May 1997 ? - we may reasonably which has a centre of intensity at l and displaying a rich variety of expect to be able to see them all = 499.5 nm. Among the resultant emission lines. (Novae would separately and so to determine sets of measures, that with the make another interesting field of their wavelengths one-by-one, smallest scatter was also the best: application for the same reasons.) and make rough visual estimates NGC 7027 (visual mag +8.5) Comets at solar distances of 0.5 - of relative intensities. This gave l = 500.8 ±3.0 nm, allowing 1.0 AU usually radiate strongly certainly has the capability of for both random and systematic the molecular bands of C2 at showing up nightly spectroscopic errors, a result only 0.3% above 473.7 nm, 516.5 (often the changes that would be quite the expected value. The miracle dominant visual wavelength) and beyond the reach of direct actually works! 563.5 (band-head l’s) and of CN imaging with or without colour at 388 nm. Sun-grazers, by filters. I would strongly urge Other sets of 4 - 6 measures were contrast, are exercises in atomic members of the Comet Section to also taken for each of NGC 6826 spectra rather than molecular add observations of this sort to the (mv = 8.8), 7009 (mv = 8.3), 7662 chemistry. An earlier and much more usual direct imaging (mv = 8.3) and 3242 (mv = 7.7) cruder attempt in this direction planned for Hale-Bopp this with a worst case result only 2.7% which I made with the same piece spring. Given that the comet will, in error, this being a rather rough of nylon 20-odd years ago yielded when sufficiently near the sun to first attempt.... and all this with a value of l = 523±15 nm for produce strong line emission, be only an altazimuth telescope, a comet Kobayashi-Berger-Milon at least 6 magnitudes brighter than piece of old nylon curtain and a on 1975 August 24. Subsequently NGC 7027, there will not be a darkroom stopwatch! I have no published professional spectra single telescope user in our doubt on the basis of these results showed the C2 band-head at 516.5 Association who will be that more careful use of this nm as the brightest visual prevented by lack of equipment primitive instrumentation would emission at that time. In addition, from making some potentially be quite capable of ±1 - 2 nm my further observations over the very interesting measurements accuracy. Theoretically, the days following gave at least a with this truly minimalist method resolving power in 1st order of strong hint of night by night - why not give it a try ? this piece of nylon is nearly changes in the spectrum. sufficient to split the sodium 'D' Reference lines. The nylon grating method clearly 1. North, G. Advanced amateur has more than sufficient spectral astronomy, pp284-6, 1991 Planetary nebulae are rather discrimination to reveal very boring objects in this sense - they quickly which of the major

CME-Fried Comets

Robert D Brown

This item was taken from the retrograde moving orbits and Hypothesis: CME's tend to have usenet and is reprinted as an arrive in the solar system from head-on interactions with example of its genre. No doubt it any direction (randomly). The retrograde-moving long period also explains the cometary origin intermediate period comets have comets that result in the explosive of Venus! Note that the author an average inclination of 28 demise of the , has not provided any calculations degrees to the ecliptic plane and while prograde moving comets which could attempt to justify the 75% move in prograde orbits. tend to have tail-first interactions hypothesis, though an order of The short period comets move with CME's that result in a slow magnitude calculation is quite within the ecliptic plane and all cook-off of comet volatiles. The straightforward. display prograde orbits. plasma-mediated magnetic connection of CME's with comet There is a potential for a parity- CME's maintain their angular tails converts parabolic orbits to breaking interaction between momentum as they traject away elliptical orbits more coronal mass ejections (CME's) from the Sun. Comet tails, in characteristic of asteroids. An and comet tails that may explain contrast, are radially-oriented in asteroid is what one gets from this the asymmetrical distribution of respect to the Sun. Because the process. comets in prograde and retrograde Sun's rotational rate is faster at the moving orbits and explain the equator than it is toward the poles, R. D. Brown, M.D. origin of asteroids as "CME-Fried the potential for a parity-breaking Pelorus Research Laboratory Comets". CME- interaction is greatest at the ecliptic plane. The long period comets are split 50-50 between prograde and

Letters

BAA COMET SECTION NEWSLETTER

Graeme Waddington points out in dodecatemorio capricorni visus from space. The latest Captain of that the period I gave for comet est, hicque spatio sexaginta Mir is Alexandr Kalery who sent Hale-Bopp in the Journal note is quinque dierum, tria signa in this reply on 1996 October 14; only true for the epoch of coelo percurrit. Hunc reception was not good and there perihelion. He goes on to say: confusiones linguarum, & are some gaps in the transmission: This is not the orbital period prior dissipationes gentium in toto to the comet’s current passage terrarum orbe, sunt secutae. De Dear Don, through the solar system, as it was quibus Genes, undecimo capite, changed as a result of the 115 prolixus textus dicunt. I saw both Tabor and Hale-Bopp million km approach to Jupiter in comet. Tabor looks like a small April 1996. The period of the Whereas Hevelius accepts this diffuse spot having size approx. previous orbit was around 4200 AM 1944 (=-2191), “record”, 7-8 arcmin. I couldn't see its tale. years - hence we should be Pingre rightly regards it as a pure Only the head was seen through looking for cometary apparitions fiction (“imaginees sans aucun its coma...... I can say nothing around 2200BC and not 500BC as fondement”), but neither Baldet about this star because it is absent implied by your wording. As it nor Hasegawa picked this up. on my star map. I can observe happens, both Baldet and (The alternative dating of -2024, this comet by binocular -20x and Hasegawa’s comet lists give a quoted by both Baldet and monocular -6x only. Hale-Bopp candidate comet visible from Hasegawa, appears to be due to comet is seen also by these Egypt in -2191 (or -2024); in both Pingre - it depends on just when instruments. But in binocular I cases the comet “record” has been you think the “flood” occurred!). saw only its head and in taken from Pingre’s Given the paucity of reliable monocular I saw its tale too. I can Cometography (1783), p 246. records from 2200BC it is indeed estimate its head size in 14-15 Pingre got his entry from unlikely that the previous arcmin and its tale 2-3 times Hevelius’ Cometographia (1668), apparition of the Hale-Bopp will longer. Now it can be seen in the p 794. Hevelius, in turn, got his be identified in the historical first 10-15 minutes of shadow in information from the Sequunter record...... (Communication was lost at Exempla Cometarum of this point, but Don thinks he was Rochenbach’s De Cometis (1600; Graeme Waddington answering the question as to how published 1619), p114 where we close to the sun they were able to find the following: observe the comets by going on to The cosmonauts aboard the Mir say that they were observing them Anno mundi, millesimo, spacecraft communicate with while in shadow before sunrise or nongentesimo, quadragesimo amateur radio enthusiasts all over after sunset.) quarto. Anno post diluvia, the world. Amongst them is BAA ducentesimo, octuagesimo octavo, Member Don Shirreff (G3BGM) Alexandr Kalery Cometa in Aegipto naturam who asked them about observing Saturni referens, circa Alcairum,

Tales from the Past

This section gives a few excerpts alter the comet’s orbit. The D Crommelin published a paper from past BAA Journals, RAS review of the year notes in the Journal on how to compute Monthly Notices and Sky & calculations by Professor the orbit of a comet from three Telescope. Plantamour of Geneva in AN, on observations made at intervals of the motion of Biela’s comet and a few days. Observations of the 150 Years Ago: Monthly gives a passage from Seneca’s Leonids were reported and Notices contained an anonymous Naturales Quaestiones which prognoses given for the review of A Historical Survey of seems to describe a double comet. forthcoming return and that of Comets’ by Dr Michelsen, which The review also records comet 1933. A good return of the seems to be a forerunner of recent discoveries of the previous twelve Bielids was also expected in books by authors such as Schaaf months, including 3 by de Vico, 1898. It was reported that Dr and Yeomans. According to the 2 by Brorsen and two by Hind. Riem had linked comet Tebbutt review it covered great and Hind had been co-discoverer of 1881 K1 to a comet seen by the periodic comets, including one with de Vico and had just Chinese in 612 BC. Mr W T apparitions of 1P/Halley back to missed out on another, but the one Lynn suggested that comet 426 BC [though modern research that carried his name alone Tewfik, seen at the solar eclipse gives returns in 391 or 466 BC]. became visible in daylight on in 1882, might be linked to was one of the few March 30. Hind also predicted a ‘certain appearances’ seen in other periodic comets observed at return of the comets 1264 N1 and photographs taken at the solar several returns at this time and its 1556 D1 for February 1848, eclipses of 1860 and 1893. If so motion was thought to however the modern orbits bear the comet would have a period of demonstrate the presence of a no relation to each other. 10.9 years; however he also resisting medium in space. F W linked sunspots to swarms of Bessel died in 1846 and his 100 Years Ago: Volume 7 of the meteors! AN 3416 contained a obituary notes his studies of BAA Journal reported that a new paper by J holetschek giving 1P/Haley, and particularly refers rule for telegraphing comets came notes on many ancient comets, to his observations of jets in the into operation on November 1, including several apparitions of coma and his realization that these when the brightness of the object comet 1P/Halley recorded by the could create a repulsive effect and was included in the cypher. A C Chinese. Linking comet orbits BAA COMET SECTION NEWSLETTER 8 THE COMET’S TALE was a popular pastime and paper on the Giacobinids and out a comet search earlier. It another attempted linkage was there was much discussion about moved north and was expected to between comet D/Lexell (17770 the storm’s relation to comet be 9m [the section archive records L1) and D/Swift (1895 Q1). Giacobini-Zinner. Also in start the following year]. The Swift had also seen a bright object reference to the shower, known as Carter Observatory of New about 1 degree east of the sun on the Draconids in the USA, Sky & Zealand issued the announcement the evening of 1896 September Tel mentions ‘No known comet of the discovery of a comet by the 21; this may have been a can itself strike the Earth’. The Director of the RAS of New . March Journal (57, 3) contains a Zealand comet Section on report of the comet Section for September 2. Berry himself was 50 Years Ago: The Reverend Dr 1946 [such reports are fairly doubtful and wanted to wait for Martin Davidson resigned as infrequent in the Journal]. confirmation. It turned out that Director of the comet Section at Section member Albert Jones had flaws on three plates taken on the AGM in October 1946 and discovered a comet (1946 P1) on separate days were coincidentally was succeeded by Dr Gerald August 6 the previous year whilst aligned. Merton. At the January meeting trying to find the variable star U Manning Prentice presented a Puppis, although he had carried

Review of comet observations for 1996 November - 1997 April

The information in this report is a synopsis of material gleaned from IAU circulars 6496 - 6640 and The Astronomer (1996 November

- 1997 April). Note that the Comet 46P/Wirtanen Comet 81P/Wild 2 figures quoted here are rounded 9 off from their original published 9 accuracy. Lightcurves for the 10 brighter comets are from 10 observations submitted to The 11

Astronomer and the Director. A 12 11 full report of the comets seen 13 during the year will be published Observed magnitude Observed magnitude 12 in the Journal in due course. 14 13 A final observation of 22P/Kopff 15 Dec Jan Feb Mar Apr May Dec Jan Feb Mar Apr May was made by Wener Hasubick on 1996 - 1997 1996 - 1997 1996 November 4.7 when it was mag 13.5. A preliminary analysis of the data gives a light curve of 6.5 + 5 log d + 12.9 log r but this is a little indeterminate. 81P/Wild 2, a target for the 118P/Shoemaker-Levy 4 never 29P/Schwassmann-Wachmann 1 NASA Stardust mission, reached became very bright, but a number was again in outburst in February peak brightness at around 10th of observers recorded it fading and early March, peaking at mag in late March and is now from 13m during the winter. around 12th mag. This comet fading slowly. Observations Observations received so far give seems to spend a lot of time in received so far give a preliminary a preliminary light curve of outburst and is worth monitoring light curve of 8.9 + 5 log d + [10] log r with CCD cameras on a regular 7.0 + 5 log d + 11.6 log r basis. not very different to the previous apparition. 46P/Wirtanen, the target for the ESA Rosetta mission, was visible for a short while in the evening sky this spring. A diffuse object, it peaked at around 10m in late March, but was not too difficult to see. It faded rapidly in April. Observations received so far give a preliminary light curve of 8.2 + 5 log d + 17.6 log r

BAA COMET SECTION NEWSLETTER 1997 MAY 9

at the RAS meeting on March 14, gave a nearly perfect straight line fit with no apparent variations.

Comet 118P/Shoemaker-Levy 4 Since the beginning of the year Comet Tabur (1996 Q1)

11 the comet brightened more rapidly 4 at -0.7 + 5 log d + 10.5 log r 5 12 suggesting that peak brightness 6 was around -0.4. 7 13 8 Observed magnitude

Observed magnitude Observed 9 14

10

15 11 Comet Hale-Bopp (1995 O1) Dec Jan Feb Mar Apr Sep Oct Nov

1996 - 1997 -2 1996

-1

0

1

2 126P/IRAS (1996 P1) was 1996 R3 Details of a faint comet recovered at 13m by Rob Observed magnitude 3 discovered by Claes-Ingvar

McNaught on a UK Schmidt plate 4 Lagerkvist on an ESO Schmidt taken by Q A Parker on August 8. plate taken last October were 5 For most of the apparition it was a Jan Feb Mar Apr May given on IAUC 6564 (1997 southern hemisphere object, but 1997 February 21). The object was became visible from the north late eventually confirmed on images in the year as it faded from 12 to taken by the Spacewatch and 13 mag during November and NEAT teams last September. It is December. an intrinsically very faint comet and may be periodic, though there C/1995 O1 (Hale-Bopp) has now C/Evans-Drinkwater (1996 J1) are not enough observations to disappeared from view to was discovered by Robert Evans confirm this. northern hemisphere observers. and Michael Drinkwater (a former There are already over 2000 PhD student at the Institute of C/NEAT (1997 A1). The NEAT visual magnitude observations, Astronomy in Cambridge) on UK (Near Earth Asteroid Tracking) and 400 graphic images of one Schmidt plates taken on 1996 Team discovered a very faint sort or another in the archive, May 10. Despite being at comet (19th mag) with the making it the most observed perihelion at the end of USAF/GEODSS telescope on comet in the Section records. December, no observations have Hawaii. It is a distant object and Although it was a '', it been reported as it has been too unlikely to be observed visually, is presumptive to call it THE great close to the sun. It is now fading however at least one UK amateur comet of 1997 - there are 8 below 13m. has obtained CCD images. months of the year to go yet! C/Tabur (1996 Q1) was visually P/Kobayashi (1997 B1) was The comet faded a little in August discovered by Vello Tabur of initially reported to the IAU by S and September last year, but Wanniassa, Australian Capital Nakano as an asteroid discovered during October brightened by Territory on August 19 at 10m. It by Takao Kobayashi, but about 1 mag and reached 4.5 to brightened rapidly and moved subsequent observations showed the in mid October. north, becoming an easy target for that it was in a cometary orbit and During the rest of the year it did northern hemisphere observers. It further observations by W Offutt not brighten much and reached broke up and faded during late showed it to have a coma and tail. 4th mag by the end of the year. It October and the last observation The nuclear magnitude of the brightened rapidly during January was made in mid November. The comet is around 17, but visual and February peaking at around - light curve is a power law best fit observations may put it brighter. 0.5 in late March. It is now over the apparition, but the This is the first amateur CCD fading. The equation observations are clearly much discovery of a comet and is also -0.5 + 5 log d + 7.2 log r fainter than this in late October the faintest amateur discovery and fits all the available observations and November. shows that the field is not lost to (corrected for aperture), but there the professional search teams. are long period variations about this mean curve of around a P/Gehrels (1997 C1). Tom magnitude. Alan Fitzsimmons Gehrels discovered a comet by has suggested that because it is a eye during the course of the very dusty comet the light curve Spacewatch survey. The comet is is better fitted by including a a periodic one, and is currently phase term and the observations 17th mag and fading. do bear this out, at least until February. A presentation by Alan BAA COMET SECTION NEWSLETTER 10 THE COMET’S TALE

C/Spacewatch. Details of the 1899, and couldn't be found in orbit of an unusual asteroid, 1997 1932. At the last return it was BA6 were given on MPEC C-13. eventually recovered some three The orbit is very eccentric, with a months after perihelion in 1965 period near 4500 years and a June. semi-major axis of several hundred AU. This is more typical The Leonid rates themselves last of a long period comet and year seem to have peaked at a subsequent observations with ZHR of around 50-60 between large telescopes showed a small 06-10 UT on November 17. faint coma. Currently it is nearly Many of the meteors were bright, 20th mag and located at around which is similar to what was seen 12 deg dec, but will be at high prior to the big display in 1966. southern dec when near perihelion. The asteroid is C/Montani (1997 G1) was currently some 8 AU from the announced on IAUC 6622. It is a earth and nearly 9 AU from the 19th mag object discovered by sun, and is heading for perihelion Joe Montani of the Spacewatch at 3.4 AU in 1999 December team. The preliminary orbit when it may be around 13th mag. suggests that it is a distant object, with a perihelion distance of 4.3 C/Mueller (1997 D1) is a new AU and will not become any comet discovered on plates taken brighter. It may be a periodic by Jean Mueller for the 2nd comet. Palomar Sky Survey with the 1.2- m Oschin Schmidt Camera on Feb C/Montani (1997 G2) quickly 17th. The object was reported as followed. It is another distant 16th mag, but appears brighter to comet, but may just become visual observers. This was visible to southern hemisphere confirmed by an observation observers when it reaches made with the Northumberland perihelion next Spring. 0.30-m refractor x170 on March 6.11, when I made the comet P/McNaught-Hughes (1997 H1 = 13.7, DC4, diameter 0.4'. 1991 S1) was recovered at its first Although it should remain around return by Jim Scotti with the this brightness until conjunction Spacewatch telescope and A in late May, no positive Nakamura with the Kuma Kogen observations have been reported Astronomical Observatory 0.6-m since early April. It should f6 Ritchey-Chretien reflector. It reappear in the autumn slightly is not expected to become much brighter. brighter than 18m .

55P/Tempel-Tuttle (1997 E1) has C/Mueller (1997 J1) is another been recovered by observers new comet discovered on plates using the Keck 10-m telescope taken by Jean Mueller for the 2nd and confirmed using the ESO 3.5- Palomar Sky Survey. The object m NTT at mag 22. The parent was reported as 14th mag, but comet of the Leonids, it will not appeared a little brighter to visual reach perihelion until 1998 Feb observers. Just past perihelion 28 when it may get as bright as and at high northern declination 9m. It will pass 0.35 AU from the when discovered, it will fade. earth in mid February when it gets within 8° of the pole. Several sungrazing comets have been discovered by the The comet was originally coronograph on the SOHO discovered on 1865 December 19 spacecraft. Formal discovery by William Tempel in Marseilles designations will be announced and on 1866 January 6 by Horace when the CBAT has sufficient Tuttle from Harvard. The comet details to give accurate positions was then around 6m and reached or orbits. perihelion on January 12 when it was 5m. It faded and was last For the latest information on seen on February 9. Once the discoveries and the brightness of orbit was calculated it was comets see the section www page: realised that it was very similar to http://www.ast.cam.ac.uk/~jds that of the Leonids and previous returns of the comet were found in 1366 (when it made a very close approach to earth, 0.0229 AU, and reached 3m) and 1699. It wasn't really looked for in BAA COMET SECTION NEWSLETTER 1997 MAY 11

BAA COMET SECTION NEWSLETTER