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Dear colleagues, I've just observed 29P/S-W with 1.0-m telescope, the comet is in outburst with pseudo-nucleus mag ~13.7R (image in attachment). Time near 2025-05-13 18:10 UT I've already sent my photometry report. Best regards, A. Novichoniok.

This is a screendump from the current MISSION 29P News Page showing the lightcurve from the last 76 days of observations. Some particularly untypical behaviour occurred between April 15 and April 24 that terminated in two mini-outbursts. Compare that behaviour with the most recent May 04 outburst that has faded rapidly. If the brightness fades past R(1,1,0) value of 9.0 there is a high probability of another mini-event. The last two strong outbursts took place on February 01.7 and 02.4, the earlier event having triggered the later one. The next time this region of the nucleus emerges from the nightside will be about May 25-30 (i.e. two revolutions of the nucleus later) when we can expect a further strong outburst. Do keep up coverage of this bizarre object as it is now approaching low solar elongation and I am keen that we follow it for as long as possible . Clear skies, Richard Miles BAA

Prior to 2014 weak outbursts had never been detected and recognised. Here are plots for both 'strong' and 'weak' events, the boundary between the two being an intensity of 4.0 nucleus-equivalents: As you can see the two phenomena differ in several ways: N.B. Other analyses show no causal link indicating that a weak outburst can trigger a strong event. Keep up the good work observers! Richard Miles BAA

It is now 68 days since the last strong outburst and 13 days since the last weak outburst so the nucleus is now visible through a relatively feeble coma. The brightness of the coma alone (nucleus contribution subtracted) is about 1.1 nucleus equivalents (mag 17.0R). About 70% of all outbursts happen when the remaining coma is brighter than it is at the moment as can be seen from this plot: The question is - How much fainter will the inner coma become before we see any sort of further outburst? Richard

The last strong outburst was on February 02.43 ± 0.05. So given the rate of fading at present, we might expect another strong outburst between March 30 and April 02. Here's the lightcurve based on the latest 251 reports / sets of images, submitted since February 24. If the strong cryo-eruption takes place then it is from the same active source region on the surface, which erupted on February 02. If so then it has taken just a single revolution of the nucleus to recharge the cryomagma 'chamber'. If not, then we may have to wait another 58 days or so! Richard

Thank you all the observers who have been contributing to the project of late. You have done well. Having lots of contributions enables us to confirm even very weak outbursts as can be seen with the March 6th event. Here's a close-up of the last 4 out of 5 mini-outbursts: MISSION 29P has been going 11 years to date during which we have witnessed 254 outbursts, 57% of which have been of the mini-outburst variety. On average we cover 82% of each apparition, losing 18% to solar conjunctions. That means that on average 29P has exhibited 28 outbursts per annum - FOUR times the number that are claimed to take place according to Wikipedia! We have detailed observations of the rise in brightness after about 10 of these and in all cases it appears that the active ejection stage only lasts a matter of minutes (max. ~10 min) after which we see the expanding optically opaque ejecta cloud increasing in size and brightness for up to 20-30 minutes. Then further expansion renders it optically transparent after several hours when maximum brightness is reached. In NO case out of >250 outbursts do we see jets develop, so when a fissure does appear it promptly empties its ejecta into the vacuum of space in one short process before resealing. This behaviour is characteristic of a classic cryovolcanic eruption in which a fluid cryomagma exists at a positive pressure beneath a consolidated crust. The rapid expansion of gas and boiling of the liquid fraction during the ejection phase extracts large amounts of heat energy from the remaining cryomagma, which quickly cools and solidifies bringing the eruption to a halt. We have also seen that strong outbursts tend to trigger further strong outbursts within a day or two, suggestive of debris falling back and fracturing the crust, or precipitating low-albedo dust that causes sealing material to warm up, soften and melt provoking the triggered event. 29P appears to be entering a new phase in its behaviour when we start to see strong outbursts only coming from one side / hemisphere of the nucleus. This phase may last another 3 years. If so, we will have a good opportunity to verify the previous 57.7-day rotation period that used the 2010-2014 observations. Maybe the retro effect of eruptions will have slowed it down slightly? Do keep up the good work everyone, Richard

2025 March 2: Stellar occultation update / Mini-outburst on 2025 March 01 discovered by Nick Quinn The past 19 days have seen the pseudo-nucleus gradually fade from magnitude 14.8R to 16.5. Yesterday, thanks to Nick Quinn observing from Steyning in the UK, a 0.4-mag outburst was detected. Thanks also to Patrick Wiggins observing from Utah about 6 hours earlier we have been able to tie down the time of this step-change in brightness to an accuracy of 0.2 days. On the occultation front, we have to thank Christian Weber and Dave Herald, who by chasing up some negative reports has managed to constrain the size and shape of the nucleus in a useful manner. Here’s a close-up view of the latest occultation chords. Still only one positive event. The path appears to have shifted roughly 170 km south of the predicted path. The two observers either side of the total occultation were Matthieu Conjat from Nice, France and Patrice Le Guen from Toulon, France. This result shows that the nucleus shape is far from being bi-lobal. Richard Miles (BAA)

Dear all, On the evening of Wednesday, February 5, 2025, there was a stellar occultation of a magnitude 13 star in Leo by the nucleus of comet 29P/Schwassmann-Wachmann. From the ALMO Observatory MPC G18 (near Bologna), the occultation is negative, even if the acquired data are still being analyzed. Regards Adriano Valvasori

I recorded from 23:04:21 to 23:19:59 at 500ms exposure (FITS). A gradual increase in brightness was recorded compared to two comparison stars. This was probably caused by the brighter part of the coma moving into the measurement aperture (Tangra). Here is my light curve. Blue is the target. I will be reporting to SODIS and the OccultPortal. Predicted mid time was around 2311 30s UT Tim Haymes Steeple Aston, Oxfordshire Y98 [ C11 F5.8, QHY174m-GPS. exp 500ms. No filter, as FITS sequence ]

From: [email protected] <[email protected]> on behalf of Richard Miles via groups.io <rmiles.btee@...> Date: Tuesday, February 4, 2025 at 4:53 PM To: [email protected] <[email protected]> Subject: [29P-ml] Stellar Occultation by Comet 29P/Schwassmann-Wachmann on 2025 February 05 23:06-23:11UT - UPDATE A reminder about this unique event crossing Europe and Asia within less than 24 hours from now. N.B. The comet had two outbursts on February 01.7 and February 02.4 so some possibility exists that obscuring material has entered a temporary orbit within a few hundred kilometres of the nucleus. Similarly some ejecta fall back onto the nucleus after a few days and this may be detected also. Observers anywhere within Europe might try to monitor this once-in-a-lifetime event as negative observations do add to our knowledge. Details of the occultation are available at the Lucky Star Predictions webpage: https://www.lesia.obspm.fr/lucky-star/occ.php?p=146316 Other details have been posted on the BAA's MISSION 29P News webpage at: https://britastro.org/section_information_/comet-section-overview/mission-29p-2/mission-29p-centaur-comet-observing-campaign The coma around the nucleus is continuing to fade so we can expect magnitude drops of between 1.0 and 2.5 mag for a total occultation, depending on the size of the photometric measuring aperture - smaller apertures yield greater magnitude drops. The expected maximum duration of the event will be about 3.5 seconds so a telescope of 0.15-m aperture or preferably larger is recommended. Video cameras or fast frame-rate CMOS cameras are recommended to provide a permanent record of the event are best to be used. Absolute timing accuracy should be high (better than 0.2 sec if possible). Video cameras with GPS time insertion are particularly good. However since the track covers areas of high population, if many timing chords are obtained it will also be useful if an observation of the 'duration' of the occultation is obtained using manual timing to an accuracy of about 1 second or better. Clear skies, Richard Miles British Astronomical Association (BAA)