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Hi Mira-Ao, It's almost certain that 2017 FL36 was active in 2017. This is my current list of items in the asteroid file which are too bright to be inactive and yet only observed on a single opposition, so you can infer that they were likely active during their one apparition. There are a few others that have been removed from this list when they were moved to the comet orbits list. The first 6 of them I'm more or less certain of. The last 3 are simply suspected as being active, and there's some small chance that they are ordinary and have simply been missed due to bad luck for the surveys in recovering them. Also, given the clear activity of 2017 FL36 in the Subaru images, it removes all doubt for me. It's a formality though that makes sense—MPC needs a second report of activity and without that it remains on the PCCP even though it's certainly an active asteroid. I also don't fully understand what the policy is regarding single-opposition active asteroids and whether they always move them to the comet orbits file or sometimes prefer to leave them in the asteroids orbit file since the orbit is asteroidal. Designation Rating TJ 2008 BJ22 0.99999726 3.198039543 2001 BV70 0.99999726 2.947403141 2019 OE31 0.9999883 3.006167013 2015 BC566 0.99998224 3.199087267 2017 FL36 0.99980015 3.221096601 2021 AY8 0.9997931 3.348862983 2015 MR207 0.9986854 3.237052317 2015 BA553 0.9982122 3.134370005 2002 CW116 0.9981375 3.319114684

Four new comets (asteroids relabelled as...) in MPECs H86, H87, H88 and H90: H86: P/2017 FL36 (PANSTARRS) -- single apparition in 2017, P=5.01 years, next perihelion in August 2025. Note that it was observed when it was closer to aphelion (~January 2018) than perihelion (June 2015, July 2020), that makes it a strange case. H87: P/2009 KF37 (unnamed) -- observed in 2001, 2009, every year between 2014 and 2017, and now 2025; P = 8.34 years H88: C/2012 KA51 (unnamed) -- quasi-parabolic, single apparition in 2012 H90: P/2010 KG43 = P/2010 PT8 (unnamed) -- observed in 2010 and 2023; P = 13.2 years Adrien

Hi all, MPEC 2025-H69 has just announced P/2010 LH155, a Jupiter-family comet whose current observations are its third observed opposition. It looks like this object was inactive in 2010 and 2018, and has only been active at the current opposition. It makes me wonder if it's an actual comet, or an object that had an outburst for some reason (rotational breakup, collision, ...). It has regular close approaches with Jupiter (1940, 1998, 2023, 2058, 2117, 2141, 2176, 2200), but the only recent one was at 0.95 au in 2023, and it slightly shortened its perihelion but not dramatically, so it is unlikely to be the trigger of this cometary activity. Orbital parameters at perihelion: Epoch=Tp / a (au) / e / i (°) / q (au) 2010-02-18 / 3.88 / 0.38 / 8.3 / 2.39 2017-09-30 / 3.87 / 0.39 / 8.3 / 2.37 2025-04-09 / 3.74 / 0.51 / 8.8 / 2.22

Thanks for sharing the link, Dan, and congrats on making APoD! Very nice shot from June Lake when the comet was looking a lot healthier than it is now! --Rob

Hi all, Statistical question: given that this (non-sungrazing) comet seems to not be new (barycentric orbital period in the 30~80 thousand years at epoch 1900), i.e. its disintegration could supposingly have happened at any other approach before or after the current one, is this seeming disintegration at this specific approach a statistically unexpectable event (i.e. expectable lifetime / number of known similarly-long-period comets >> orbital period), or is it statistically not unlikely (i.e. expectable lifetime / number... << orbital period) -- and even more, unlikely or not to happen within "modern astronomy" (i.e. expectable lifetime / number... >> or << centuries)? Thank you in advance for your help. Adrien

Hi All. Just now was released CBET 5538 and SWAN25F = C/2025 F2 (SWAN)! My congratulations to Michael and Robert! Great job guys! I am also grateful to each and everyone who took part in this case - I proud that I can be a part of so good and so powerful astro-community. Also many thanks to Daniel Green and to CBAT and MPC staff. Vladimir.

Hi Michael and Vladimir, I actually have Michael at 11 SWAN comets (or 12 if you count 58P which Michael spotted in SWAN in April 2020) C/2004 H6, C/2004 V13, P/2005 P3, C/2005 T4, C/2006 M4, C/2015 C2, C/2015 F3, C/2015 P3 , C/2020 F8, C/2021 D1 and C/2025 F2. If my records are correct, I have Vladimir with 7 SWAN comets (some shared with Michael and/or me): P/2005 P3, C/2011 Q4, C/2012 E2, C/2015 C2, C/2015 F3, C/2023 A2, and C/2025 F2 My count is at 9 (many of which also shared with Michael and/or Vladimir), though as Michael pointed out one of these (C/2012 V4) turned out to be the recovery of D/1827 M1 = 273P Pons-Gambart, and another P/2018 HT3 was linked to an asteroid. --Rob From: [email protected] <[email protected]> On Behalf Of Michael Mattiazzo via groups.io Sent: Friday, April 11, 2025 3:57 PM To: [email protected] Subject: EXTERNAL: Re: [comets-ml] C/2025 F2 (SWAN) + coordinate conversion check Thanks Vladimir. I’m sure Rob has also found quite a few over the years, including some non SWAN named ones such as 273P Pons-Gambart and P/2018 HT_3 The recovery of 58P was also a SWAN find. cheers, Michael From: [email protected] <[email protected]> On Behalf Of Vladimir Bezugly via groups.io Sent: Friday, 11 April 2025 6:02 PM To: [email protected] Subject: Re: [comets-ml] C/2025 F2 (SWAN) + coordinate conversion check Hi Michael. If I correctly understood this - we all should to congratulate you with a TEN comet that you discovered in the SWAN data! So my congratulations to you with this milestone! Vladimir.

Good afternoon, everyone. How do I obtain map of constellation in SWAN, STEREO images? I've seen these several times but I don't know how to get them And also calculating approximate right ascension and declination. (also from SWAN) Regards,

Dear Vladimir and Michael Mattiazzo: I am *relieved* that CBAT 5538 provides the missing timeline and important details of all the independent discovery work carried out by not only the three of us in measuring the comet’s very coarse astrometry in SWAN, but the essential confirmation attempts undertaken by a small army of ground-based observers cued by our ephemerides. I was a bit crestfallen by the short shrift given in MPEC 2025-G102 to the importance of the discovery observations and measured astrometry by Vladimir, Michael and myself. (After 12+ manhours of back-and-forth with MPC by Bill Gray and myself, we were finally able to get SWAN astrometry accepted by MPC.) SWAN comet finders all know going in that we have no naming rights – that the comet will get a SWAN name designation, just as SOHO and STEREO comets are named after those respective spacecraft/instruments. Brian Marsden (R.I.P.) understood and appreciated the contributions of “citizen scientists,” and so he was supportive of at least publicly crediting these discovery efforts. I thought perhaps that MPEC 2025-G102 would follow the precedent of 2023-D49 which provided clear credit to Vladimir for the discovery of C/2023 A2 (SWAN) in its opening paragraph: https://minorplanetcenter.net/mpec/K23/K23D49.html This was the first time ever that SWAN astrometry actually appeared in an MPEC. But, alas, none of those discovery details were given in MPEC 2025-G102: https://minorplanetcenter.net/mpec/K25/K25GA2.html No mention of Vladimir, and indeed there would have been no mention of Michael Mattiazzo in the MPEC if not for his iTelescope follow up observations using U94. The 249 astrometry reported happens to be mine (due to the somewhat excruciating efforts of Bill Gray and myself mentioned above), but I should think Michael’s or Vladimir’s would have been equally valid (though perhaps missing the SWAN instrument details), and their astrometry was reported to CBAT up to two days prior to mine. The bottom line is that we need a better reporting and acknowledgment system. Comets first found in SWAN data are quite rare – now just 21 of them since 1997 – and at least a couple of those discoveries reverted to prior designations (e.g. P/2018 HT3). The SWAN experts who do this work (are there even a dozen of us alive?) have surely earned some recognition for their hundreds if not thousands of hours’ work per actual comet discovery. --Rob From: [email protected] <[email protected]> On Behalf Of Vladimir Bezugly via groups.io Sent: Tuesday, April 8, 2025 5:53 PM To: [email protected] Subject: EXTERNAL: [comets-ml] C/2025 F2 (SWAN) Hi All. Just now was released CBET 5538 and SWAN25F = C/2025 F2 (SWAN)! My congratulations to Michael and Robert! Great job guys! I am also grateful to each and everyone who took part in this case - I proud that I can be a part of so good and so powerful astro-community. Also many thanks to Daniel Green and to CBAT and MPC staff. Vladimir.

Hi all, If you didn't check the WGSBN website, just to inform you that the WGSBN has assigned names to three comets that were up to now unnamed: - C/2015 K7 (COIAS) - P/2023 S1 (PANSTARRS) - 471P/LINEAR-Lemmon Adrien