Endlich Durchblick! / Alle grossen Brocken unten: Report#13 22.7.1994 18:10 CST (spaeter als sonst, aber aus gutem Grund: Selber gucken ging vor...!) ------------------------------------------------------------------------------- "I've got a 4-meter telescope ready, and here I'm observing with a 4-inch..." John Spencer konnte es kaum fassen, aber es gab keine Alternative: Nachdem hef- tige Schneefaelle nicht nur den Cerro Tololo sondern auch die Teleskopkuppeln bedeckt hatten, erlaubte Berg-Direktor Oskar Saa in dieser Nacht das Oeffnen nicht (aus gutem Grund: eine heftige Schneelawine loeste sich bald darauf von der 4-m-Kuppel) - auch als es ENDLICH in der Nacht aufzuklaren begann. Ausser dem wundersamen Mini-Newton, den jemand in der Casa Dos (wo die Radioastronomen hausen) deponiert hatte, stand mithin kein Geraet zur Verfuegung, und so wurden die Beobachtungen kurzerhand verlagert. Die beiden Spektroskopiker aus Korea und Frankreich kamen mit, Brad Schaefer natuerlich und John - mehr haetten auch kaum in den Jeep gepasst, der als einziger die zugeschneiten Strassen befahren durfte. Die Spektroskopiker hielt es nicht lange, die beiden visuell orientier- teren Herren brachten dagegen die Geduld auf, das Auskuehlen des allzuwarmen Tubus abzuwarten - und dann sahen wir alle (mit vielen Sigma Zuverlaessigkeit, wie die Beteiligten betonten), wie sich der dunkle Fleck um die Impaktregion Q dem Zentralmeridian naeherte und ihn gegen Mitternacht passierte. Trotz der zu geringen Vergroesserung (die mitgebrachte Barlowlinse passte nicht...) und schlechten Seeings in 25 Grad Hoehe war der dunkle Fleck mindestens so auffael- lig wie das NEB und v.a. dunkler - wenn auch dermassen weit im Sueden Jupiters, dass er bei besonders schlechter Luftruhe mit dem Planetenrand und dem dunklen Weltraum dahinter zu verschmelzen schien. Heute nun begruesste uns strahlend blauer Himmel, und John konnte schon gegen 16:00 mit IR-Beobachtungen beginnen. Der Planet ist weiter voll heller 'Plumes' und hat ein "Mysterium" zu bieten: Date: Fri, 22 Jul 94 13:18:59 MST From: John R. Spencer Subject: Dark spot in North at 1.58 microns We are observing again, in daylight, at the CTIO 4-meter. At 1.58 microns, continuum, we see a prominent dark spot in the NORTHERN hemisphere, eyeballed at about 15 N, approaching the meridian at about 20:00 UT. The impact sites in the south are not prominent at this wavelength, thogh we are seeing them at 2.3 microns. as usual. No, it's not a satellite shadow.... ANyone else seen this or can explain it? John Spencer, Darren Depoy, CTIO 4-meter, OSIRIS. Aber zurueck zur vergangenen Nacht: Am Center for Astrophysics stand der tra- ditionelle oeffentliche Abend am 9"-Clark-Refraktor bevor, und man fuerchtete nicht zu Unrecht, von Menschenmassen ueberrannt zu werden. Susannes Bericht: Oh weia..... Jupiter ist gerade hinter den Baeumen verschwunden, und ich habe mich vom Dach davongeschlichen, bevor die Menschenmenge, die 2 Stunden geduldig in der Schlange stand, ueber mich herfallen konnte, weil Jupiter untergegangen ist und sie ihn nicht gesehen haben... Aber viele haben ihn gesehen, da es hier erstaunlicherweise richtig klar wurde. Ich habe ich mich voellig heiser geredet, hatte zuerst die angenehme Aufgabe, Jupiter im 9" zu zentrieren, so dass ich ihn oefter zu sehen bekam - aber dann hat das jemand anders uebernommen und ich habe mich vor der Kuppeltuer postiert und Leuten Voraberklaerungen gebenen, damit es am teleskop schneller ging. Extrem schwierig - man kann die Leute nicht nach 10sec wegzerren, besonders, wenn sie Jupiter vorher noch nie gesehen haben, aber was macht man, wenn dahinter noch 200 Leute warten... Diese Erklaererei draussen vor der Tuer war eine gute Sache, und fuehrte zu mancherlei Diskussionen - aber anstrengend. Wir hatten drei, vier andere Teleskope draussen, und in einem 6" Newton kann habe ich Fleck K ganz gut gesehen, aber das ist nichts richtiges fuer Joe Public - in so einem kleinem Teleskop muss man *wissen* wonach man Ausschau halten muss. Dass spannendst aber passierte noch vor Sonnenuntergang. Als ich nach oben zum Teleskop ging, so gegen 7 pm (die Sonne stand noch hoch), beobachteten neben ein paar anderen Leuten Dan Green und Steve O'Meara -- Jupiter am Taghimmel, mit einem dichten Orangefilter. Der Kontrast war natuerlich mies, aber Fleck K war gut sichtbar, und das Adlerauge Steve hatte in kuerzester Zeit auch A und C ausgemacht. A habe ich auch eindeutig gesehen. Und dann sagte Steve: "K is double. There's a small, dark spot trailing it." Ich checkte meine Liste und Meinte: "Ja, kann sein, da ist der neue Impakt U, der zu dem Zeitpunkt gerade eine Stunde alt war, und der nur 6 Minuten nach K im Transit sein soll" Daniel nickte erst, und meinte dann "Unmoeglich. U ist voellig insignifikant, es ist ein Fragment, das ziemlich verschwunden ist. Aber na gut, ichwerde mal meine Mail checken." Kurze Zeit spaeter kam er wieder und sagte: "U gibt es nicht - drei non-detections sind berichtet worden." Steve schaute wieder und war voellig unbeeindruckt. "It IS there. Foolish professionals - I see it. They just don't look in the visual. Put it out on the exploder, Dan - it's there." Groessere Aufregung .... und die Oeffentlichkeitsscharen begannen, das Dach zu stuermen. Irgendwie haben Dan und Steve zwischendurch immer wieder mal geschaut, und ich versuchte, gleichzeitig Erklaerungen abzugeben und mit ihnen zu diskutieren. Ich habe K iebrigens nur deutlich elogiert gesehen... Und es blieb weiter spannend: Wir alle drei und ein weiterer der Public Night helfer sahen klare Struktur im Fleck L, der danach kam, und zwar einen ganz dunklen Fleck, der von der ueblichen "Bull's Eye + smudge" Struktur raeumlich getrennt war. Steve sah das wieder klarer als wir anderen - wenn er uebrigens schnell was skizziert, ist das eine so gute Planetenzeichnung, wie der normale Beobachter sie *nie* hinbekommt.... An dieser Stelle sollte nun nach Liste gar nichts sein - ein unbekanntes Fragment ?? Mystery Spot ?? Dan meinte, mnche Bilder wuerden Einzelsites doppelt zeigen, also war es vieleicht "nur" eine interessante Substruktur... Wieder weiss ich nicht, ob die beiden "uber den Exploder etwas herausgejagt haben... sie tauchten noch ein- zweimal in dr Kuppel auf und schafften es, kurz durchs Teleskop zu schauen (und das Bild dabei wieder zu zentrieren) --- aber ich kann Dir sagen, dass das ein Moment echt grosser Aufregung war und ich Joe Public gerne losgeworden waere... aber auch der Oeffentlichkeit gegenueber hatten wir eine Verpflichtung. Ich habe das f:ur Leute, die die aufgeregten Diskussionen mitbekamen, dann umgedreht - bestimmt wuerden sie merken, wie aufgeregt wir waeren und daran sehen, was fuer ein aussergewoehnliches Ereignis sie miterlebten.... Hier nun aus dem Mail-Exploder die Chronologie der restlichen Impakte: We successfully observed the R impact from the 200-inch Hale telescope at Palomar, with simultaneous observations at 3.6 microns, 5 microns, interleaved with 10-micron spectra at 10-minute intervals. The first indications were seen at 5:35 UT at 3.6 and 5 microns. We recorded rapid brightening of the site at 5:41, reaching a peak at 5:46 UT when diffraction spikes were observed at 5 um. 5-um flux dimmed by a factor of 40 by 5:50 UT. The image was observed to be extended along the limb at 5:51 UT and approximately 2" long at 5:54 UT. By 5:59 UT, the 5-um flux had dropped to the level in the first images. After approximately 6:00 UT, the 10-um flux appeared to be constant. By 6:12 UT, the 5-um feature had faded to a brightness comparable with the planet. At 6:23 UT, the 5-um feature was almost gone, at an airmass of 4.17. By 6:39, impact site Q also appeared on the eastern limb. Observations ceased at 6:50 when the horizon limit was reached. Colleen McGhee, Phil Nicholson, Gerry Neugebauer, Keith Matthews, Tom Hayward, Jeff Van Cleve, Alycia Weinberger, John Miles, Dave Shupe Observations from San Pedro Martir Observatory (SPMO) confirmed a quick R flash. It was seen visually by the telescope operator through the finder telescope as a flash off of one of the satellites (he didn't identify which one) through a 6" reflector. An observer at the .84m doing photometry saw a flash 2 minutes after the predicted time on the SE limb of Jupiter. Observations with the NICMOS Camila camera at 2.2 um confirmed a flash about 15 minutes after the predicted time, approximately Jul 22 22:45. In the IR at 2.12 um the flash was a very quick brightening, a matter of minutes--the exact times are difficult to determine due to the closeness of the G spot. It also faded rapidly--again in just a few minutes. Since the signal was much lower than the L flash reported yesterday, it is more difficult to pin down the times more reliablly wihtout further reduction (and you know how much I hate instant science...). At 2.12 um, it brightened to a flux greater than Io for a brief time. Jim Klavetter (CSUS) et al. The W.M. Keck Observatory comet impact team reports: At UT 5:33 (July 21) we detected the FLASH from impact R: it lasted for maybe 20 seconds: truly remarkable. Approximately 8 minutes later the plume appeared, brightened considerably and faded again over a period of approximately 8 minutes. Based upon weather conditions (clouds, high cirrus), we observed in a narrow K-band filter (2.3 micron; 1% CO filter). Frames were obtained every 7.5 seconds, with an integration time of 4.2 seconds. We are momentarily closed due to high humidity. Imke de Pater, James Graham and Garrett Jernigan. PS. Yesterday we detected the impact from the "lost fragment M", at around 6:08 UT. The impact site was clearly separate from that of K, which came into view a little later. July 21 (UT). The NASA/Infrared Telescope Facility reports observing a bright plume associated with the impact of fragment R, at 5:40 UT, using the MIRAC2 mid-infrared array camera. The fireball was observed at wavelengths of 7.85, 10.2, and 12.2 um at intervals of 50 seconds per cycle. The emission increased at all three wavelengths for 5-10 minutes, then decayed on a slower time scale. At its brightest, the fireball's surface brightness was at least 50 times that of Jupiter at all three wavelengths. The NASA/IRTF Comet Collision Science Team THE IMPACT OF FRAGMENT R OBSERVED BY IRIS ON THE AAT We are continuing to use the InfraRed Imaging Spectrometer (IRIS) on the 3.9 m Anglo-Australian Telescope (AAT) at Siding Spring Observatory (near Coonabarabran, Australia) to monitor the impacts of Comet Shoemaker-Levy 9 with Jupiter. On 22 July, observations were initiated at 04:28 UT. The the sun was still high in the sky (2:28 PM local time) but the sky was clear, and the seeing was initially about 1 arcsec. K- and H- grism image cubes of the Jovian disk were recorded between 4:30 and 5:30 UT. Images extracted from the K-grism cubes initially revealed the impact sites of fragments K and L as bright clouds in the morning and afternoon hemispheres at about 45 S latitude. We could not easily distinguish the impact site of P2 from that of the K impact. K-grism drift scanning was used to monitor the R-fragment fireball with an integration time of 1.5 seconds per slit position. In this mode, we obtain spatially-resolved (0.6 arcsec/pixel), full-disk spectral image cubes (R ~ 300) of Jupiter once every 2 minutes. The detection of the fragment R impact fireball was a special challenge because it occurred while the sun was up, and because it was predicted to occur just as the the impact sites of fragments D and G were approaching the morning limb. In addition, the seeing worsened to 2-3 arcsec just before the predicted impact time, further complicating the detection of the predicted impact fireball. A distinct, bright, point-like source first appeared on the morning limb at 05:34 UT. This feature was tentatively identified as the impact fireball from fragment R. At 05:42, as the seeing improved, this feature brightened dramatically, saturating the detector at 05:45:33, and producing distinct diffraction spikes, like the fireballs associated with the impacts of fragments G and K observed earlier this week. Just before saturation, the feature was at least 200 times brighter than the South Polar Hood at 2.34 microns. The telescope was stopped down to 2.3 m to bring the detector back on scale at 05:47 UT. The brightness of the feature was still about 200 times brighter than the South Polar Hood at 05:48 UT. By 05:50, its brightness had decreased by at least a factor of 25. The mirror was therefore re-opened to its full 3.9 m aperture. At approximately 06:00 UT, a bright feature came over the limb. We could not determine if this was the impact site of fragment R, or that of G, D, or Q2. We are continuing to monitor these impact sites. SPIREX observed the fragment R impact on the Bullseye at 05:44 UT. Our preliminary estimate is that the impact site was as bright as event E, at 2.36 microns. Again, the South Pole has been experiencing intermittent cloud, but the sky was clear around the time of impact. We are also starting to make some progress reducing the several thousand frames taken at approximately hourly intervals in several narrow band filters over the entire course of the impact sequence. We expect to have almost uninterrupted coverage of the impact sequence and subsequent evolution of the impact sites. Does anybody know what the record for continuous observations of a single object is? Mark Hereld, Hien Nguyen, Bernard J. Rauscher, Scott A. Severson Astronomy & Astrophysics Center, University of Chicago The W.M. Keck Observatory comet impact team reports: At UT 5:33 (July 21) we detected the first FLASH from impact R, followed within 45 sec by a second FLASH; each FLASH lasted for 15-20 seconds: truly remarkable. Approximately 8 minutes later the plume appeared, brightened considerably and faded again over a period of approximately 8 minutes. Based upon weather conditions (clouds, high cirrus), we observed in a narrow K-band filter (2.3 micron; 1% CO filter). Frames were obtained every 7.5=20 seconds, with an integration time of 4.2 seconds. We are momentarily closed due to high humidity. We observed the fireball from the impact of Fragment R, using the Steward Observatory 90-Inch. The fireball became visible at about 05:42 UT, July 21 and persisted for about 6 minutes. A spectrum was obtained over the range 2.29 to 2.355 microns, with spectral resolution of 3500. The spectrum shows a complex molecular band which we identify as CO emission, redshifted by the expansion of the fireball. Milagros Ruiz, George and Marcia Rieke, Dennis Means The impact plume of fragment S was detected at 15:29 UT with the MAGIC camera on the 3.5m telescope at Calar Alto Observatory in the 2.3 micron range. It became brighter than the nearby spots of previous impacts within about 2 minutes after detection. Starting from 15:33 UT it started fading eventually reaching the level of the other bright spots. Due to electronic problems we were not able to record the event from 15:18 to 15:28 UT. In images taken with 4 sec time resolution up to 15:18 UT the S impact was not visible. A very large dark ring is seen surrounding the impact site which moved onto the limb at about 10:02 UT 21 July. (perhaps the L site?) The ring extended beyond the south pole, and nearly to the equator, imaged using a Bessell blue filter and CCD detector. The central impact site was also dark in this filter. Where this ring intersected Jupiter's dark band at about 20 degrees south latitude (belt? zone?) the methane image shows a bright spot. The impact site is not bright in the methane (8900 A, 300 A wide) This complex was seen to move across the face of the planet in successive images taken between 9:24 and 10:38 UT. By 12:46 poor seeing prevented seeing it. This feature was marginally visible in a narrowband sodium filter, but not in a Cousins R filter. These observations are part of the Comet Impact Network Experiment headed by Steve Larson of the University of Arizona. Ellen Howell Mount Stromlo Siding Spring Observatory 1m telescope At this point in time (21 July 1994 3:30 EDT =3D 19:30 UT), the Hubble Space Telescope Team has not yet seen evidence for any rings other than the small discrete rings which closely surround the largest impact sites, and the larger ejecta blankets generally to the south of each feature. It is possible that our temporal and spatial sampling is not optimal for seeing these large scale phenomena. The G impact created the largest site yet seen. Many of the sites (including G) appear larger near the limb than they do near the central meridian due to enhanced scattering. All detected phenomena at impact sites were and still are bright at the 8890-A methane band. Imaging was also obtained at 9530, 5550 or 5470, 4100, 3360, and 2550 A (virtually all detected phenomena at impact sites were dark at those non-methane wavelengths). Heidi B. Hammel, for the Hubble Space Telescope Team Clouds in central Baja, Mexico, have allowed us to do a more accurate reduction of the R impact "flash" (for wont of a better name--it does NOT appear to be the same as the visually observed flash since the time is 15 minutes later than the reported visual times). We observed around the R impact time with the Camila IR Camera at 2.122 um (narrow H2 filter). Althhough the conditions were not photometric, both Io and Europa were on the chip and not saturated. By comparing the photometry of the G spot which was just on the limb with Io and Europa we were able to do fairly accurate photometry. The flash we saw corresponded to the G spot spatially so the excess was due to the R impact. We find that the rise time was incredibly fast and distinctly different than the larger L impact flash seen the day before. The flux increased by a factor of 2 in less than 1 minute (no mistake--1 minute). It stayed at max brightness for about 5.5 minutes at a nearly constant level, and then was down to near its pre-brightness levels in again less than 1 minute. It was brighter than Io at maximum and total rise was about a factor of almost 200%. Although not as bright as the L impact flash, this one seems remarkable in its own way and seems like it might be physically different than L, rather than just being scaled down in size/mass? As a ps, did anyone notice how odd the K spot looked? Maybe there was an M impact after all? Jim Klavetter (CSUS) et al. We report observations of the T impact starting at approximately 20h UT, (before sunset). The T impact site showed spatial structure down to the sub-arcsecond level different from that observed in other impact sites. More specifically the arcs extended to the northeast instead of to the southwest of the impact spot. Until approximately 23:30 UT with Jupiter at a high airmass no obvious U impact spot was detected. The Arizona-Florida-Spain Team at the 4.2 m WHT, La Palma. On the night of July 21 we continued to monitor the eastern limb of Jupiter with the 3.5m and 2.2m telescopes at the Calar Alto Observatory. We observed no sign of the T impact (which occured here before sunset). The T impact site was on top of the E and F spots which made identification of an event difficult. The U fragment was predicted to strike in the old K site. We saw a brief rise in the brightness of the region at 22:10 lasting perhaps a minute. If this was the U impact, then it certainly was unlike previous events! 22 July 1994 (UT): Table Mountain Observatory 1.2m, Wrightwood, CA. We started observing Jupiter at 0:55 UT in 8900 A filter, 1 sec integration time. We are able to discern the impact site of fragment U as it transits the central meridian. We also observed (what I think is) a combination of sites G+D+R rising over the western limb at 1:0UT. We stopped temporarily to pull up the wind cover as the winds seem to have picked up. The sky is rather clear right now. In repsonse to Jim Bell (of Lick Observatory) message earlier today, I agree with his explanation of why observers using 8900+/-100A cannot observe bright spots on Jupiter. We are using narrow band filters (50A wide) at 8900,9450, 7270,7500,6184 A filters. We observe the spots to be bight with some dark cores in 8900 A, but dark in all the other filters. Milagros Ruiz, Dennis Means, G. & M. Rieke observing at the Steward Observatory 90-Inch searched for the V impact, which had not occurred (at least no fireball) by 35 minutes after the predicted time. Conditions were clear, seeing was 1", we were looking at the right planet, no excuse. NON-DETECTION OF THE IMPACT OF FRAGMENT V BY THE AAT We are continuing to use the InfraRed Imaging Spectrometer (IRIS) on the 3.9 m Anglo-Australian Telescope (AAT) at Siding Spring Observatory (near Coonabarabran, Australia) to monitor the impacts of Comet Shoemaker-Levy 9 with Jupiter. On 22 July, observations were initiated at 03:34 UT. The the sun was still high in the sky (1:34 PM local time) but the sky was clear, and the seeing was initially about 2-3 arcsec. K-grism image cubes of the Jovian disk were recorded between 03:30 and 04:00 UT. Images extracted from these cubes initially revealed the impact sites of fragments H, the N-Q1-Q2-R-S-D complex, and L as bright clouds distributed between the morning and afternoon hemispheres at about 45 S latitude. Starting at 04:00 UT, we switched to rapid-sampling imaging photometry with a 2.34 micron filter to search for the impact flash of fragment V. The readout time was 0.45 seconds. The detection of this impact was particularly challenging because (1) it occurred while the sun was up, (2) fragment V was expected to be one of the smaller fragments, and (3) the impact was predicted to occur just as the the impact sites of fragments H,F, and T were near the morning limb. No distinct flash was detected before 04:33 UT, at which time a faint, but distinct feature moved over the morning limb. The slow, steady increase in brightness of this feature suggests that it was the impact site of fragments F or T, rather than the fireball for V. After a few tries, I think we are finally getting it right. Unfortunately, it seems as if the comet has fizzled the last few fragments. V continued the trend. No brightening in H2 (2.2 um) with careful photometric and time resolution here at SPMO in Baja, MX. =20 jjk for SPMO team 22 July 1994 (UT): Table Mountain Observatory 1.2m, Wrightwood, CA. We are still observing Jupiter as long as we can as the impacts come to a close. We ended observing at 6:345 UT. The GRS spot had crossed the central meridian. Impact site for fragmetn Q was approaching the e. limb as we all bid adieu! Padma A. Yanamandra-Fisher, Steve Gillam, Robet Fisher, Jim Young and Joe Spitale (TMO). SPIREX observed the fragment W impact at 08:14 UT. Our preliminary estimate is that the impact site was as bright as event E, at 2.36 microns. The last 30 hours or so at the South Pole have been severely affected by cloud. The clouds cleared around the time of impact, and the view of the impact was described by the observers at the Pole as "Beautiful!". The clouds have set in again. We are hoping that the clouds will clear for some reasonable fraction of our remaining thousand odd observing hours tonight. Mark Hereld, Hien Nguyen, Bernard J. Rauscher, Scott A. Severson Astronomy & Astrophysics Center, University of Chicago No evidence of the impact of fragment V was seen at 2.34 microns on the ANU 2.3 m telescope at Siding Spring Observatory. The impact of fragment W was detected at 2.34 microns as a slight brightening over a pre-existing impact site at UT 08:06. This appeared to fade by UT 08:09, and reappeared strongly beginning at UT 08:10. Our detector saturated at UT 08:13 as the impact site came into view. Narrow band imaging between 3 and 5 microns beginning at UT 08:17 showed strong emission at 4.78 microns associated with the impact site, but no evidence was found for a wave moving out from the impact site, as we have observed after other large impacts. Peter McGregor and Mark Allen Mount Stromlo and Siding Spring Observatories Australia Das waren also die grossen Einschlage - nun heisst es beobachten, was mit den grossen entstandenen Wolken in den naechsten Tagen und Wochen passiert. Z.B. A: From: Jim Bell LICK OBSERVATORY CROSSLEY 36" REPORT Subjects: Apparent Dark Ring around impact site A Detectability of impact sites using 8900A filters Images obtained from Lick using a high speed CCD camera system on 20 July UT confirm the reports of Howell and others from Mount Stromlo that there is a possible large dark ring surrounding the A impact site. A mosaic of some of our images (processed using a blurred mask filter) called crossley.gif is available in the /ftp/incoming subdirectory on pdssbn.astro.umd.edu. The caption to the image is called crossley.txt We observed the impact sites using Bessel U,B filters and narrowband 7500A, 8600A, 8900A, and 9500A filters (FWHM = 100A). In B images obtained from 0400 to 0500 UT on 7/20 we observe a large dark arc-like structure extending from the south pole up to -20 degrees S latitude and centered on the A impact site (which was also dark in our B images). The arc has a radius of roughly 10 arcsec. The structure is also visible in our U band images but is not visible in any of our narrowband filters. There are at least two immediately obvious possible explanations for this feature: (1) it may be the visible expression of an expanding shell (or wave) of material from the A impact site: the feature is large because the A site is oldest; (2) it may be an artifact introduced by a combination of 2-arcsec seeing and the fortuitous alignment of the GRS and H impact site along an annulus concentric to the A site. In the exploder report by Howell, the bright spot in the methane filter at the intersection of the dark ring and Jupiter's dark -20 degree band is probably the GRS. Also, the impact site on the dawn limb in the Howell image is most likely the A site. Jupiter's aspect was nearly the same at 4 hours UT on 7/20 and 10 hours UT on 7/21. Jim Bell, Ted Dunham, Dominique Toublanc, Bob Thompson Lick Observatory Crossley 36" Observing Team Weitere Instant Science wie ueblich von den NASA-Pressekonferenze, diesmal gleich von zweien, gestern und heute und zusammengefasst von S.Huettemeister: NASA Select Comet Update / July 21 8 am EDT Disclaimer: Sorry, I forget my notes at home and wasn't quite awake when I watched this, so this is fairly sporadic and garbled, possibly even wrong On the panel this morning: Hal Weaver, Rita Beebe, Lucy McFadden, Gene Shoemaker, David Levy Most striking (picturewise) to me was the first presentation of "real color" pictures from HST, of (among others) impact site G. The colors were pastellish and fairly subdued, so maybe theu were really close to "real colors". I know from Heidi Hammel herself that she likes it that way and is really worried about strange impressions brought forward in the mind of the public by garish false colors. Anyway, clearly this is one of the pictures mentioned day before yesterday (I think) proving how thin the "dark stuff" truly is. At least one of Jupiters regular bands was visible quite ckearly through the "impact blanket", even on a TV screen with less than prefect picture quality. And the impact site was clearly the by far most prominent thing visible on Jupiter's disk - but we got used to that, haven't we :-) ? Beebe stated that she really got into this whole business because she was hoping to study Jupiter's winds by watching the impact material spread out (in longitude, mainly). But this doesn't seem to be really happening - she stated that the impact related material and the tropospheric wind seem to be very well "decoupled" at this point. This might change with time (and isn't at least spot A slowly expanding?), but right now if might give poor cloud shrouded Cerro Tololo another shot, even after the last impact tomorrow. By the way, in a color picture, the spots appear dark brown rather than red. She also showed a picture that had a little something related to the Q impact. Having read other reports, I'm now more confused than before, but this is (roughly) what she said: They only have data from one HST orbit processed yet, and something is just coming around the edge of the planet. She stated that this was (maybe) Q2, definitely "the baby of the group", the smallest impact site seen so far. But in brightness, the pre-impact fragment Q2 was 10x stronger than A. So why did it cause such a "wimpy" site? Speculation: Q2, like B and another one that was also weak and the name of which escapes me, were "out of line" with the other fragment, possibly ejected later (?) and physically different (ie less solid, more "rubble pile" like), so that they form a different class of impactors. But that should mean that Q1 should have been brighter, and she didn't say a word about Q1. Weaver showed a picture taken of the Q region just 10 hours before impact. The point was to study if Q1/Q2 disintegrated further when falling toward Jupiter. His findings: They clearly didn't. However, the dust "coma" betwenn them got stretched out, and the 2 fragments also where separated by a larger distance, and seemed almost aligned, while in earlier pictures Q2 was "above" Q1. They impacted on Jupiter 12 deg in longitude apart. Gene Shoemaker was especially excited by the fact the *the impact of fragment M has been observed at Keck*. It was a tiny impact compared to others, but M was a fragment that disappeared last year. The debate was if it disappered because it didintegrated entirely, or bacause it "shut off" its activity. Shoe- maker had been firmly siding with the people who favoured "shut off" - and if the impact of this fragment was really seen, it seems he was right. Beebe added thta the Keck observer who noticed this didn't report it for a day - she noticed it, but it wasn't on her list, so she didn't believe it. Only a talk on the phone with Beebe convinced her otherwise. Amateurs: David Levy again encourages everyone to go ahead and look at Jupiter. But it seems that he himself hasn't seen it yet - he complained: "All these dinners - every time it clears up, I have to *eat*! I can't wait to get back to Tucson." Other observatories: Lucy Mcfadden had a report from Galileo, concerning the impact of fragment L, which was luckily caught, because its impact time changed. The brightness of the initial flash was described as " 4-6% of Jupiter's brightness ". There was also something from an UV satellite (McFaddeb said IUE, the caption said EUVE, so I don't know) - they got good observations of the impact sides, but see no brightening of the Io plasma torus so far. In the Q/A, one well informed journalist asked about flashes seen not from the moons (there were none) but from the ring of Jupiter. There seem to have been claims that such a thing was seen at least once. And someone asked why everyone had predictes a fizzle when it turned out to be such a great show --- Gene Shoemaker grinned pretty comfortably and explained that *some* people (including him) had really predicted things to be pretty close to what we see. Then he explained the usual stuff about the uncertainties in determining fragment sizes. NASA Press Briefing 2 pm EDT, July 22 --------------------------------------- On the Panel: West (JPL), Andy Ingersoll, Gene Shoemaker, Lucy McFadden, David Levy * Shoemaker confirmed that all fragnments have hit. W was quite visible, but U and V were "fizzles" - which was expected, since they were small to start with. Dan Green, with whom I watched this, speculated that W, like A, might have been and "end piece of the comet", thus physically slightly different and possibly making a bigger splash than expected from its size. * There are a lot of really nice true color HST pictures around now, showing lots of spots with complex and changing structure. The panelists themselves got confused noe and then about spot identifications, so all idents I make are slightly doubtful... * There's a very nice UV HST picture out, showing various dark spots. Obviously, this was taken after the impact of R (its site is there) and before S (not present). West stated that we are seeing UV absorbing dark material that will alloe us to trace stratospheric wind with time. He suspects that the effect will be fairly longasting - the number he mentioned was actually "up to year", which is the longest I've heard so far. But he does expected the spots to have blnded together and mixed a lot till then. But it seems to be a valid question if we'll see something after Jupiter reappears in the morning sky after conjunction. * Waves: Andy Ingersoll very confidently interpreted the thin dark ring around site G in the famous HST image 1 1/2 h after impact as a sound wave, 4000 km in radius at the time, and expanding with a velocity of 800 m/s, which is the sound speed in hydrogen at the right pressure on Jupiter. I haben't seen later HST pictures about the evolution of this ring yet, however. There are some very confusing reports on the net (also discussed in the briefing, without much further enlightenment) on the discovery of possible seismic waves. There seem to be 2 reports about a visually (!!) visible dark ring that extends well beyond the south pole in one direction and almost to the equator in another. However, one group identified its center tentatively with L, while the other claimed that it was centered on A. If any of this is true, said Ingersoll, the natural interpretation of a ring this big is a seismic wave. * David Levy finally got to see Jupiter yesterday from the USNO in Washington (with Tom Wilson, I presume...). He said that the seeing was truly terrible in the 26", so they could get hardly any sort of a steady picture in there - but that he found it much easier to see in the 26"'s finderscope. * Lucy McFadden admitted that she tried to observe, but confused Jupiter with Venus at first... laughter from the panalists.... She then reported from other obdervatories: * Cerro Tololo and La Silla report nothing but clouds (seems to have changed), while Mauna Kea reports a hurricane. * Keck does however show a 9 panel IR sequence of the (I think) impact R producing its fireball right on top of the existing Q site. "These data will keep astronomers busy for years." * The KAO reports good results for R - they claim to have seen "new emissions, not reported so far", and they conclude (preliminary, obviously) that the explosion took place at rather high altitudes. * The UK Infrared telescope reports the tentative discovery of *water* (!!) at 2.407 mu from impact R. * The IUE looked not at Jupiter for a while, but at the chain of impacting fragment. They think they see UV emission from the fragments along the chain. * They also went back to the plume pictures above the limb and pointed out that in the first moment (when the fireball rises) it's glowing from its own heat, which is why it's visible immediately, on the dark side of the planet (remember - Jupiter shows a slight phase to earthbased observers!) Later, this fades and we see the material (in HST pictures, that is) illuminated by sunlight, that is *above* the dark limb and the shadow cast by the planet (this is easier to visualize in the graphic that they showed...) Mehr nun direkt vom HUBBLE-Team, Instant Science und neue Zahlen: The HST comet team has analyzed a 39-minute time sequence of the G impact, showing the growth and decay of the plume on the limb of the planet. The objective is to estimate the lag between impact and visual phenomena as the plume rises to an altitude where it is visible from Earth if it is self-luminous, and then to an altitude where it is in sunlight. Based on the 16 July 1994 predictions of Chodas and Yeomans, these altitudes are 550 km and 2900 km, respectively at the instant of impact, but they decrease with time as the impact site rotates toward the dawn terminator. We estimated the impact time from position on the disk 90 minutes after the event. The error of this determination is about 2.5 minutes, as described in two earlier messages concerning impacts A,B,C,D,E,G,H. More such determinations are coming tonight (21 July 1994). Time Altitude above limb Appearance 7:32 0 Impact (from later observations) 7:35 500 Self-luminous, unilluminated 7:37 900 ditto 7:40 1600 Arc-shaped, top of plume in sunlight 7:43 1200 ditto 7:46 900 ditto 7:49 500 ditto "Altitude above limb" is perhaps a misnomer, since the dark limb is about 500 km above the terminator, and we have enhanced the contrast mercilessly to bring out every last photon in between. So treat the altitudes with 500 km uncertainty. The plume is visible at 889 nm and 953 nm when it is still in shadow. In sunlight, its brightness is comparable to that of Jupiter near the terminator. The shape is that of a capital D rotated counterclockwise by 90 degrees. For the G plume at least, the time interval from impact to when the plume was visible in sunlight was 4-8 minutes. Andy Ingersoll and John Clarke, for the HST Comet Team Far-UV Images of Jupiter with HST: Dark Regions and Auroral Arcs! The HST WFPC 2 and FOC have obtained images of Jupiter at far-UV wavelengths roughly 1-2 times per day since 13 July. Images cover 1150-2100 A, which shows Rayleigh scattered solar continuum over 1700-2100 A and auroral emissions at H Ly alpha and H2 bands over 1150-1650 A. The FOC images one auroral region at a time, while the WFPC 2 images the whole planet including impact sites and both polar auroral regions. We have baseline images from late May and June with both cameras which are by far the best UV images of Jupiter's aurora ever obtained. These indicate the morphology of the "normal" Jupiter aurora, which have been seen to vary on timescales of 5-10 min. when there are no comets falling into the atmosphere. To date, the UV aurora have appeared somewhat fainter than in May in the WFPC 2 team images, and fainter than average to IUE observers (IUE observations have been obtained since May 1979). In the L = 6-30 areas the auroral morphology is similar to that observed in May, without obvious changes associated with the comet passage. We do see multiple latitudinal band structure in the north auroral emissions near 150-180 deg., which appears well resolved in the short 400 sec images (less blurring from rotation than in May). Most of the far-UV images this week have been near 200 deg. CML, due to timing and to track the C, A, E, F, and K impact region changes. In the first post-impact WFPC 2 images, taken after the C, A, and E, we have seen large dark regions in the scattered solar continuum over 1800-2100 A in the F160W (Na Wood's filter) bandpass. These region are similar to F218W and F255W images, and larger in extent and darker than the visible images. One of these was released to the press last Monday and is now all over the world in .gif format. Each of the large impact sites appears dark and extended in the far-UV: the continuum level is less than 1/2 the level outside of the dark regions. These dark regions appear to be spreading with time, but slowly. To date, the G and L sites are the largest in the far-UV and very impressive, each being larger than the great red spot. In contrast with the lack of clear changes in the auroral regions, we have detected bright "arcs" apparently associated with the K impact region. Two images roughly 45 min. after the K impact show arc-like auroral emissions near the approaching limb at mid-latitudes in the north, and fainter but similar emissions near the conjugate points at the K impact site in the south. The north arcs are of the order of 20-30 kR in brightness, which at that time was as bright as the northern aurora. The arcs are clearly fainter in the second image, indicating a decay in brightness on a ~10 min. time scale. No arc-like emissions outside of the "normal" auroral ovals were detected in quick looks at additional images: - 1 hour before and 30 min. after the P impact - 2 hours after the R impact - 2 hours after the W impact We have overplotted magnetic field lines from the O6 model, starting at the north arcs and extending to the south atmosphere. The conjugate points in the south are close, but not exactly, on the fainter diffuse emissions which border the K impact region. The maximum radial distance of the outer field line is 2.1 Jovian radii, suggesting source plasma originating either from the K fragment within a few x 1000 km of the atmosphere or in the plume itself. A preliminary overlay of long/lat lines gives extents of the emission regions in degrees (planetographic latitude, system III longitude): (56,258) to (56,238) - brighter northern arc (52,277) to (51,257) - less bright northern arc Ground-based observers with images of Jupiter's H3+, etc. emissions may detect comparable emissions from these features, especially in observations taken near and within 1 hour after the impacts. Please examine your images in the north as well as the south! Reports from IUE observers indicate enhanced H Ly alpha emission and possibly some H2 emission also from the vicinity of the K impact site near the time of impact: see yesterday's message from Gilda Ballester. The first of two WFPC 2 images with overplotted field lines will be placed on the stsci.edu bulletin board later today. John Clarke for the HST UV Imaging Team - dazu passen Neuigkeiten vom IUE: Observations of the Jupiter system have been performed with the IUE satellite on a 24 hour basis since the 15th of July, and intermittantly since early June. The IUE imaging spectrographs have a combined spectral coverage from 1150-3300A at resolutions from .14 to 6A. We are monitoring several of the best studied upper atmospheric features of Jupiter and its magnetosphere including the Aurora, the LY-a equatorial anomaly, and the Io torus. We have detected changes in some of these features (in particular, the aurora has been weak) that we attribute to (or at least find suspiciously coincidental with) the effects of the comet fragment impacts and/or to the passage of dust through the inner Jovian magnetosphere. The IUE is also being used to monitor the development of spectral features in the impact areas, and in particular has been useful for showing the timescales that describe the development of the dark features seen in the WFPC-II images. The A, B, E, G, K, and Q impacts have been observed wiht great success. For instance, our analysis of spectra obtained on the approaching and receeding limb while we followed the G impact site with the IUE small aperture show that the region experienced a 50% drop in reflectivity as it rotated moved across the disk of the planet. Many possible absorption and emission features have also been observed in spectra obtained from the impact sites. We have not as yet had an opportunity to analyze these features properly. We are also performing an unprecedented number of simultaneous observations with other instruments. This is providing new insight into the characteristics of features long studied with the IUE, and gives the operators of the other instruments an opportunity to compare the results of their observations with the more than 15 years of Jovian FUV spectra in the archives. Along with our European collaborators, we will continue to monitor the effects of the impacts on a 24 hour basis with the IUE until the end of the week, and then on a less regular schedule until it becomse unobservable with the satellite on Aug. 15. Walt Harris; for the IUE US science team 7/21/94 We report on the likely detection of H-Lyman alpha emission off the Jovian limb associated with the plume of the impacts of fragments K, and P2 using the modest imaging capabilities of the IUE satellite. Although the PSF at Lyman-alpha is 4-5 arcsec, the emission peaks near/at the limb, and there is also quite extended,weaker emission within the 9"x21" aperture possibly 3-4 arcsec above the limb. Some molecular hydrogen emission is also detected (it appears less extended compared to the H-Lyman alpha, although this could be the effect of low S/N). Impacts Q and R have also been observed but not imaged with the small 3" aperture. Gilda Ballester for the IUE US-Vilspa observing team. Nun zu den taeglichen News der Auswertung von Spektren aller Art: We observed extremely strong CO overtone band emission in a 2.2-2.4 micron spectrum of the R impact at approximately UT 5:45 July 21 with the CGS4 spectrometer at UKIRT, Mauna Kea, Hawaii. The CO emission faded on a timescale of 10 minutes. The overtone emission implies gas temperatures of several thousand degrees K. Roger Knacke et al. JUPITER: DETECTION OF CS2 For the Hubble Space Telescope (HST) team, K. S. Noll, Space Telescope Science Institute, reports the following result: We have identified CS2 in spectra of impact site G obtained with the HST Faint Object Spectrograph. At least 13 separate bands from 1873 A to 2064 A are clearly observed. In the same spectra we have previously positively identified S2, enhanced NH3, and we have tentative evidence for H2S (see IAUC 6031). CS2 is an expected product of shock and/or solar EUV induced chemical reactions between H2S and CH4. We have also searched for bands of SO and SO2, but no band from either molecule has been observed. The two spectra were obtained at 10:43 and 11:05 UT on 19 July 1994, more than three hours after the impact of fragment G. The 0."9 arcsec aperture was positioned at the center of the impact site. A preliminary analysis of the CH4 emission at the time of impact H from IRSPEC-NTT observations. We have performed a quick-look analysis of the IRSPEC data recorded in the 3.50-3.56 micron region shortly after impact H. Our sequence started on July 18 at 19:46 UT, about 10 minutes after its detection by the TIMMI camera, at a rate of 1 spectral image per minute. During about 30 minutes, the signal of the impact region was dominated by the emission of CH4, through 5 multiplets of the nu3-P branch (J=3D14 to J=3D18). A spatial average over the presumed impact region shows that the signal intensity decreases exponentially with a time scale of about 5 minutes. The IRSPEC spectrometer with its 4.4" slit aligned along the parallel of the impact (l=-44 deg), allows a spatial analysis in this direction. The spatial resolution is 2.2". At the beginning of the sequence, the CH4 emission extends over about 10". Its spectral shape shows drastic variations along the slit, corresponding to a large range of rotational temperatures. The peak of intensity at the center of the emission corresponds to a rotational temperature of 800K. On the leading side, the intensity is weaker, but the rotational temperature is a few thousand degrees. 15 minutes after the beginning of the sequence, this hot region cools down to about 1000K, while the intensity peak has a rotational temperature of 500K. There is a weak H3+ emission on the leading side of the impact region, but no H3+ in the region itself. J.A. Stuewe, G. Wiedemann, T. Encrenaz, R. Schulz Report from IRAM 30-m observations. After the announced detection of CS2 by the HST team, we have searched CS in impact sites K, L, Q1 and T on July 21, UT 16-22. The CS(5-4) 244 GHz line was detected on site Q1, with an integrated intensity of 3.2 +/- 0.12 K km/s and a width (FWHM) of about 4.7 km/s. The CO 230 GHz was also readily detected on this site, with similar characteristics as the CS line (i.e. several times more intense than in previously observed sites E,G,H,K). Data reduction for other sites is in progress. We also report unsuccesful searches on site K (on July 20) for CH3OH and HC3N near 218 GHz. E. Lellouch, R. Moreno, G. Paubert, M. Festou The CO emission spectrum obtained from the R impact fireball at the Steward Observatory 90-Inch has been reduced more thoroughly with the following results: We see a bandhead and about 40 emission lines, making the identification as CO totally unambiguous. There are two possible explanations for the shape of the bandhead. In one, the emission band is near zero velocity and there is an absorption CO feature shifted by about one resolution element (80 km/sec Nyquist sampled for our spectrum) to the red. The emission lines become apparent on the other side of this absorption at about 2.295microns. The second interpretation would be that the bandhead is redshifted to 2.295 microns, giving a recessional velocity of about 200 km/sec. This second possibility seems less likely given the geometry of the event and the rate at which the fireballs are seen to expand in imaging experiments. These results appear to be in excellent agreement with the independent observations with the UKIRT; the higher spectral resolution of our data complement the greater coverage they achieved. In one of our previous messages, we said that we have detected CH4 nu3 band emission, which has not been unambiguously detected before on Jupiter. We prepared a postscript file that contains the obtained spectrum and a model of the nu3 band of CH4. The observations were done on the CTIO 1.5 m telescope with the new IRS around (UT) 0:00 July 17 on the impact site A. The model contains Jupiter and Earth atmospheres, and the effects of the Doppler shift between Jupiter and Earth. We used auroral temperature-pressure and enhanced CH4 mixing ratio above the 1 mbar level. As seen in the model comparison, we did not see any notable H3+ emission lines around 2830 cm-1, where several H3+ lines occurs. We have put the postscript file in pub/impact on sunkng.lowell.edu. The userid is anonymous, and follow displayed instruction after putting in the userid. The file name is CH4NU3SiteA.ps. Sang Kim, Christophe Dumas, Jay Elias, Richard Elston. A gif format image showing four KAO spectra of the K fragment's fireball in the 7.7 micron region has been posted to pdssbn.astro.umd.edu in the directory /ftp/incoming. It is called KAO_K_frag.gif and is accompanied by a short text file KAO_K_frag.txt. The image shows four long-slit spectra at a resolution of 9000 using KEGS on the Kuiper Airborne Observatory. The spectra were taken at UT= 10:28, 10:39, 10:53, and 11:04. The fireball is clearly evident in the 10:39 image. Images were taken roughly every 40 sec, so this is a small sample of the total data obtained. A cursory analysis of the light curve gives a 1/e time of approximately 8 minutes. The mean methane emission at peak increased by about a factor of 30 compared with the pre-impact emission. In the last image, the mean emission is still a factor of 4 brighter than the pre-impact emission. The 7.7 micron region is a sensitive thermometer of the jovian stratosphere sounding levels between 1 microbar and 10 millibars, far above the visible clouds. This region is totally blocked by methane in the Earth's atmosphere - it cannot be observed from ground-based telescopes. The KAO is the only observatory capable of investigating this spectral region. An important objective of our KAO investigation is to determine the level at which the cometary fragments exploded. We had 2 water channels (at 22.6 and 23.9 microns) in addition to the temperature channel at 7.7 microns. The 2 water channels are more difficult to interpret. Subtle changes will have to be investigated carefully. Our extremely preliminary examination of the water data suggest the following: the explosion did not take place at the 10 bar level on Jupiter. Otherwise we would have seen strong H2O emission lines in each of our 2 water channels due to the transport of water vapor in a rising plume. Second, the bulk of the energy was not deposited near the 200-millibar level; otherwise, the continuum level at 22.6 and 23.9 microns would have increased dramatically. Our positive detection of enhanced CH4 emission and the non-detection of jovian water and non-detection of elevated temperatures at 200 millibars suggest that the explosion of the G and K fragments took place in the stratosphere. We emphasize that these results are very preliminary as we have looked at only a small fraction of our spectra in a hangar at the airport in Melbourne, Australia after an exhausting series of flights. The high spectral resolution of the KEGS instrument reveals individual emission lines of C-12 and C-13 CH4. At least 2 unknown emission lines were observed in the spectrum of the fireball. These may be due to high excitation states of NH3, which, if confirmed, would provide evidence that the K fragment penetrated to levels deeper than 200mbars in Jupiter's troposphere. We would like to thank everyone associated with the KAO as well as our hosts in Australia for a successful flight program. Gordon Bjoraker (NASA/GSFC) Terry Herter, Susan Stolovy, George Gull, and Bruce Pirger (Cornell Univ) We have observed an emission line at 2.407 um during the R impact. The wave elength is coincident with the wavelength of an H2O line. The observed feature changed to absorption a few minutes after the peak of the event and then faced a way. This mimics behavior of CO lines we reported earlier. The observation is a provisional detection of H2O. Corroborating observations (on upcoming impacts) are highly desirable. Further observations at Mauna Kea are highly unlikely where the weather oulook is grim. Roger Knacke et al. Nun noch tiefer in den Radiobereich hinein, zuerst mit Nachrichten von Ulysses: REPORT FROM THE ULYSSES UNIFIED RADIO AND PLASMA WAVE (URAP) TEAM Ulysses, from its vantage point high over the sun's southern polar region, has a direct line of sight to the impact areas. The URAP instrument covers the frequency range of 1 kHz to 1 MHz with very high sensitivity. This frequency range encompasses several of Jupiter's known radio components and these components are quite regularly and easily detected by URAP. We have now processed URAP data through the Q impacts and have NOT detected any clearly identifiable radio emission associated with the impacts. Both Jupiter and the sun are very active, but not out of the ordinary. We will continue to analyze our data in search of more subtle or long-term effects due to the impacts, but at this stage we are not hopeful that anything will be revealed. M. L. Kaiser, R. J. MacDowall, M. D. Desch, W. M. Farrell, R. G. Stone Goddard Space Flight Center, Greenbelt, MD 20771 Und Radio-News erdgebundener Teleskope, oft nur muehsam zu interpretieren: CAUTIONARY NOTE CONCERNING RADIO DETECTION OF COMET IMPACTS We would like to caution observers concerning the several announcements that have come from various amateur groups of positive detection of decametric radio bursts associated with the comet impacts. Jupiter is a continually active planet with a highly predictable radio burst morphology. The University of Maryland's WWW pages contain a listing of the MAJOR predicted decametric storms throughout the impact period. While we don't doubt that amateur groups with modest equipment can detect Jovian bursts, one must first compare these detections with the predicted level of Jovian activity. Additionally, some of these reported detections appear to have occurred during daylight hours. We point out that the sun is rather active at present and solar emissions can be confused with Jovian emissions. For example, with the Ulysses radio astronomy instrument (URAP), we have detected 19 type III solar bursts just on July 19! M. L. Kaiser, M. D. Desch, and R. J. MacDowall Goddard Space Flight Center, Greenbelt, MD 20771 At RATAN-600 site we are monitoring daily thermal radio emission of Jovian disk (1.3; 2.7; 3.9cm), size and flux from Jovian radio emitting belts (7.6; 13; 18; 31 cm) and decametric bursts at 10m and 20m not very far from local meridian. At 10m well visible burst of activity appeared within 1- 2 min of time from object E impact time as really observed (E-mail information) and within 5 min from ITA (Russian) early prediction. Waiting confirmation from other observers. Variations of the belt radiation also visible (about 10%) in horizontal polarization but not in vertical one. Connection with cometa induced fenomena should be checked later. Y.Parijskij with RATAN-600 observers. Abschliessend noch Gedanken zur Signifikanz der Effekte fuer Jupiters Aussehen: At the U.S. Naval Observatory on 22.1 July UT, I observed the L and G impact sites through a variety of large and small telescopes. Both sites are very dark, and L has an unusual kidney-bean shape. I agree with Clark Chapman; these are the most obvious features I have ever seen on Jupiter, and with the exception of Saturn's recent white spot, the most obvious feature on any planet. David H. Levy In a 19 July message, Clark Chapman proposes that the SL-9 impacts have produced "the most visually prominent discrete spots ever observed on Jupiter." There is nothing in the photographic record of Jupiter to dispute this assertion. What about the pre- photographic era? References to size and contrast are scarce because the principal interest in jovian spots before the twentieth century was the determination of rotation period and (later) wind speed. Still, here is a list of candidate spots that were considered "promi- nent" in their time: 1690 - G. Cassini observes a spot in the SEB that "autant a peupres qu'en occupe toute l'Affrique." 1778 - W. Herschel draws three dark equatorial spots on Jupiter. Each occupies less than 1/10th the planet's diameter. 1834 - G. Airy writes of "a remarkable spot seen on the apparent southern belt, nearly four times as large as the shadow of the first satellite." 1850 - W. Dawes and W. Lassell see STZ spots, "two being nearly equal in size, and almost as large as the third satellite appears . . ." 1872 - O. Lohse draws a possible South Temperate White Oval. It slightly exceeds the Earth's diameter in longitude, but not latitude. Having last night (03:00 UT) visually observed Jupiter through the 0.2-m telescope at the Hillside Observatory, I agree with Chapman that we are witnessing spots that would have amazed the great planetary observers of the 17th, 18th, and 19th centuries. [Reference: Hockey, T. *A Historical Interpretation of the study of the Visible Cloud Morphology on the Planet Jupiter: 1610 - 1878*. Las Cruces: NMSU, 1988. (Doctoral Dissertation)] Thomas Hockey University of Northern Iowa P. S.: Many thanks to Anne Raugh and team. The Exploder was a watershed event in the way observing campaigns have and will be conducted. Recht hat er! Nun aber huschhusch an die Fernrohre - auch die Kuppel des eigentlich stillgelegten 16"ers hier hat schon jemand aufgemacht. Da sage noch einer, professionelle Astronmen wuessten den Blick durch ein Okular nicht mehr zu schaetzen... Oder ist es das "Ereignis des Jahrtausends", das zu ungewoehnlichen Massnahmen (siehe ganz oben) verleitet? Euer D. Fischer