Updated 2024 November 29
When observing a comet please try to forget how bright you think the comet should be, what it was when you last viewed it, what other observers think it is or what the ephemeris says it should be.
The equations for the light curves of comets that are currently visible use only the raw observations and should give a reasonable prediction for the current brightness. If the comet has not yet been observed or has gone from view a correction for aperture is included, so that telescopic observers should expect the comet to be fainter than given by the equation. The correction is about 0.033 per centimetre. Values for the r parameter given in square brackets [ ] are assumed. The form of the light curve is either the standard m = H0 + 5 log d + K0 log r or the linear brightening m = H0 + 5 log d + L0 abs(t - T + D0) where T is the date of perihelion, t the present and D0 an offset, if L0 is +ve the comet brightens towards perihelion and if D0 is +ve the comet is brightest prior to perihelion.
The order given here is provisional and based on the logical sequence of linked orbits. The final numbering scheme does not seem to follow this logical pattern.
This should have been numbered 405 if given in sequential order.
Erwin Schwab recovered the comet in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain. on 2020 September 11.09. The indicated delta-T correction to the prediction, by Gareth Williams, on MPC 58118 is -0.15 days. [CBET 4847, MPEC 2020-R159, 2020 September 14]
This should have been numbered 406 if given in sequential order.
The comet is a distant object and reached perihelion at the end of June 2003. The period is 18.5 years and the perihelion distance 3.93 au. Observers contributing to the preliminary orbit included BAA Member Peter Birtwhistle.
Erwin Schwab recovered the comet in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain. on 2020 August 18.11. The comet was some 5' from the expected position. [CBET 4835, 2020 August 19] It was finally given a designation for the return in MPEC 2020-S155 [2020 September 23].
This should have been numbered 403 if given in sequential order.
The Mt Lemmon Survey discovered a comet on 2020 October 15.45, which was placed on the PCCP as C3HU5C2. Hirohisa Sato subsequently realised that this was a return of 2007 VQ11 and it was withdrawn from the PCCP. CBET 4869 and MPEC 2020-U169 were issued on October 22. The comet was some 22' from the expected position, corresponding to a delta T of around -1.9 days.
Syuichi Nakano found images of the comet in PanSTARRS 1 data taken with the 1.8m Ritchey-Chretien on 2020 June 17.55 and on July 17 and 20. The comet was close to the expected position. The comet passed 0.97 au from Jupiter in 2020 February in an encounter that reduced the perihelion distance from 4.8 to 4.1 au and the period from 12.7 to 10.3 years. [CBET 4831, 2020 August 16] It was finally given a designation for the return in MPEC 2020-U182 [2020 October 23]. It was numbered 404 in CBET 4898 [2020 December 18], though it should have been 400.
An object briefly appeared on the PCCP as P218YG3 before being transferred to the "Previous NEOCP Objects" page having been identified as a return of comet 2013 TL117, though it was given on the page as 2013 TL17. The PCCP recovery was by by PanSTARRS 2 on 2020 October 25.6. Shortly afterwards further details were given in MPEC 2020-U231 and CBET 4874 [2020 October 25/26]. These reveal the continuing tensions between the MPC and CBET. Erwin Schwab had recovered the comet on October 17.13 with the Calar Alto 0.8m Schmidt (not Calar Alto-Schmidt as given in the MPEC). Additional independent recoveries were made at the Dominion Astrophysical Observatory on October 22 and by T. Ikemura and Hirohisa Sato on October 23/24.
Comet 2007 R2 was recovered during observations with the Korea Microlensing Telescope Network-SSO 1.6m reflector on 2020 September 11.64, when it was around 22nd magnitude. PanSTARRS 2 recorded it two days later and the Korean group made further observations on September 15. All these observations were published in MPEC 2020-S188 as observations of 2007 R2, though none of the observers realised that it was a recovery. [2020 September 25] Syuichi Nakano of the CBAT later noticed the observations and drew attention to the recovery. T. Ikemura and Hirohisa Sato made follow-up observations on October 10 and 12, with PanSTARRS 1 observing it on October 20. The comet was missed at the 2014 return and passed 0.74 au from Jupiter in 2016 March. The encounter increased the perihelion distance to 1.6 au and the period to 6.8 years. The comet was at perihelion in September. [CBET 4884, MPEC 2020-U269, 2020 October 30/31]. The CBET yet again hints at the tensions between the CBAT and MPC.
D Carson Fuls discovered a comet of 19th magnitude in Mt Lemmon Survey images taken with the 1.5m reflector on 2019 December 21.53. It was placed on the PCCP as C1N4PQ2 and confirmed by other observers including Michael Jaeger and Eric Bryssinck. [CBET 4709, MPEC 2020-A91, 2020 January 7/8]. The comet was at perihelion at 2.1 au in 2020 January and has a period of around 6 years.
Sam Deen has shown that the two comets are identical. The comet passed 0.34 au from Jupiter in 2010 in an encounter that significantly changed the orbit. [CBET 4792, 2020 June 8].
The comet should have been numbered 397, but the MPC have ignored the convention of numbering in order of orbit determination and returns. An MPEC announcing the identity was finally published on 2020 November 11 [MPEC 2020-V67].
Only the name Novichonok was originally given to the comet, however the discoverer was clear that it was a team effort with Gerke, and the name was later amended.
Denis Denisenko noted
As usual, there's a whole story behind the new discovery. This comet was caught just 63 (!!!) pixels from the edge of 1330x890 CCD image in 3x3 binning mode in the first night. Upon posting at NEO Confirmation Page most people (including myself) originally thought it to be identical to 111P (whose predicted position was less than 5' away, yet the magnitude was almost identical to the new object). But the direction of motion of the Comet Novichonok was totally different from Comet Helin-Roman-Crockett, and the new object was about twice slower.Congratulations to Artyom with the first Russian periodic comet since the breakup of USSR! If you remember, two Comets Elenin were discovered on the telescope installed in USA. This time the observation was made in southern Russia, in the Republic of Karachay-Cherkessia in northern Caucasus, not far away from the 6-meter BTA telescope.
Syuichi Nakano found images of 2011 R3 in PanSTARRS 1 data taken with the 1.8m Ritchey-Chretien on 2020 June 20.49 and July 18.36. The comet was close to the expected position. The comet was put into its present orbit during a series of encounters with Jupiter: 0.87 au in 1992 October, 0.11 au in 1993 August and 0.45 au in 2005 April. Prior to these encounters the comet was in a more distant orbit with perihelion at 5.2 au and a period of 19.4 years. [CBET 4833, 2020 August 17] It was finally given a designation for the return in 2020 November [MPEC 2020-V78, 2020 November 12].
According to the MPEC the comet was recovered on 2020 November 3.49 by the Zwicky Transient Facility with the 1.2m Oschin Schmidt and by the Mt Lemmon Survey with the 1.5m reflector on November 16.51. The indicated delta-T correction to the prediction by G. V. Williams on MPC 75706 is -1.08 days and it was some 30' from the expected position. The CBET gives priority to the Mt Lemon Survey for reporting a new comet and then drawing attention to the likely identity with 2005 XA54. [CBET 4885, MPEC 2020-W25, 2020 November 17] The comet has perihelion at 1.8 au in 2021 January and a period of 14.9 years.
Erwin Schwab recovered comet 2007 B1 as a stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on November 17.13. The comet was some 20' from the predicted position, requiring a Delta(T) of -0.89 day. [CBET 4903, MPEC 2021-A66, 2021 January 7/9]
Brian Marsden noted on MPEC 2010-F69 [2010 March 23] that further [astrometric] observations of this comet were desirable.
The comet is one of those suspected to have undergone nuclear splitting according to the list of Marcos & Marcos [Dynamically correlated minor bodies in the outer solar system, MNRAS, 474, 838, 2018 February]. They note that it appears to be related to the multiple fragments of 332P/Ikeya-Murakami.
Quanzhi Ye recovered comet 2010 B2 in images taken with the 4.3 m Lowell Discovery Telescope on December 19.46. The recovery confirms the identification made by Sam Deen of a single observation made by the DECam on the Cerro Tololo 4 m reflector in 2015 June. [CBET 4904, MPEC 2021-A76, 2021 January 8/9] The comet passed 0.075 au from Mars on 1999 February 18. It passed 0.44 au from Jupiter on 1962 November 12 and 0.72 au on 1974 October 11. The comet will pass 0.51 au from Jupiter on 2045 September 12
Erwin Schwab recovered the comet as a stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2020 November 25.17. [CBET 4910, MPEC 2021-A147, 2021 January 11/12]
An object was discovered by the Zwicky Transient Factory on January 5.1 and posted on the PCCP as ZTF01on. It was summarily removed on January 8 and noted to be P/2016 J3. The previous evening Maik Meyer had discovered the identity, computed a linked orbit and informed the MPC and CBAT. Maik's linked orbit shows that the period is 4.67 years, with perihelion at 0.53 au on January 25. Despite this it was not designated 2021 A1. Michael Jaeger has imaged it, finding it to be around 14th magnitude.
Sam Dean notes:
It's caught in a Kozai resonance with Jupiter that it's currently on the higher-e, lower-i leg of. I think that'll peak around 2400-2500 before cycling back. Like plenty of Earth-crossing Kozai oscillating objects, its orbit also crosses Earth sometimes, creating a potential for meteor showers. It last crossed Earth's orbit within 0.1 au in the 1300s, coming as close as 0.07 au - and it will next do so in the 2200s/2300s, coming less than 0.01 au around 2300, where it should create a fairly regular and impressive meteor shower considering that it would be even more active than it is now.Sam also suggests that the absolute magnitude is very faint, around 23 and that it brightens rapidly, perhaps at 20 log r.
Rather belatedly the CBAT issued CBET 4911 on January 11, with a revision
coming 15 minutes later. This gives a similar account to that given above
and notes that the comet will pass Jupiter at 0.9 au in 2031 December. It
also hints that either the comet shows strong non-gravitational forces or that
the 2016 positions are somewhat out. The MPC finally issued MPEC 2021-A157 on January 12.
This does not give elements for 2016, although the published elements for 2021
and 2025 do use observations from 2016, so it may
just be an oversight.
J J Gonzalez made a visual observation of the comet
on 2021 January 16.78 from his mountain observing site, estimating it at 9.7 in
his 20 cm SCT.
The comet was acccidently recovered in astrometry taken by PanSTARRS on 2020 December 25.57. It was independently deliberately recovered by Erwin Schwab as a stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2021 January 13.01. The comet will pass 0.5 au from Jupiter in 2033 December in an encounter that will increase the perihelion distance to 3.8 au. [CBET 4918, MPEC 2021-B17, 2021 January 16/17]
Erwin Schwab recovered the comet as a nearly stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2021 January 14.01. [CBET 4919, MPEC 2021-B21, 2021 January 17]
Erwin Schwab recovered the comet as a nearly stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2021 January 17.23. The comet passed 0.48 au from Jupiter in 1952 August and will pass 0.43 au from the planet in 2024 September in an encounter that will increase the perihelion distance from 1.49 to 1.57 au. [CBET 4920, MPEC 2021-B118, 2021 January 22/23]
An object recorded at 22nd magnitude in astrometry taken by PanSTARRS 2 on December 23.49 was subsequently identified as as a return of 2010 A5 by the MPC. It was also detected by PanSTARRS 1 and Mt Lemmon later in 2021 January. [CBET 4928, MPEC 2021-B140, 2021 January 29]
Erwin Schwab recovered comet 2015 F1 as an apparently stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2021 January 13.06. Additional observations were made on February 10, 13 and 14. The comet was some 4' from the predicted position, implying a delta T of -0.2 days. The comet passed 0.46 au from Jupiter in 1975 December in an encounter that substantially reduced the perihelion distance. The comet is significantly fainter at this return than it was at the discovery return. [CBET 4933, MPEC 2021-D104, 2021 February 16/25]. In what seems to be competition between the CBET and MPC the MPEC was issued nine days after the CBET.
In 2009 October Rob Matson found images of the comet on three Heleakala-NEAT images from 1996, which in turn allowed him to find it in two more nights from 1998. It was very bright in the 1996 images showing obvious coma, but barely detectable in 1998.
Erwin Schwab recovered the comet as a stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2021 March 11.13. The recovery was confirmed by Diana Abreu using the 1.0m reflector at the ESA Optical Ground Station, Tenerife on March 14. The comet was some 9' from the expected position and does not reach perihelion until 2022 May. When Syuichi Nakano computed a linked orbit the observations showed that non-gravitiational parameters were required. When these were included it was found that the 1996 observations reported by Rob Matson were of the comet, though his 1998 measurements did not fit so well. [CBET 4943, MPEC 2021-F07, 2021 March 16/17]
Brian Marsden noted on MPEC 2009-Y57 [2009 December 29] that further [astrometric] observations of this comet were desirable.
In 2021 May the MPC linked isolated tracklets from PanSTARRS and Mt Lemmon made in 2020 April and May to 2009 U4 (P/McNaught). [CBET 4971, MPEC 2021-K101, 2021 May 31] The comet was at perihelion at 1.6 au in 2021 January, about 6 days earlier than predicted, and has a period of 11.4 years.
Cristovao Jacques recovered the comet at the SONEAR observatory on 2021 June 5.32. Taras Prystavski independently recovered the comet on 2021 June 15.75 using the 0.5 m iTelescope at Siding Spring, some 9' from the ephemeris position. The recovery was reported on the comets-ml on June 15/16, with Jacques noting that he had sent the observations to the MPC 10 days previously. The MPC is a bit behind with processing comet observations and did not announce the recovery until June 17 [MPEC 2021-M34, CBET 4979]
The comet was recovered in astrometry taken with the Gemini North 8.1 m telescope at Mauna Kea on January 9.27 and January 15. The comet passed 0.7 au from Jupiter in 1921 and 0.9 au from the planet in 1986. These encounters modified the elements, but kept the perihelion distance between 5.2 and 5.6 au. [MPEC 2021-M89 CBET 4992, 2021 June 26]. The MPEC does not say why there was such a long gap between the observations and announcement.
Images of the comet were found in incidental PanSTARRS 1 asrometry taken with the 1.8m Ritchey-Chretien on 2021 June 6.53. It was independently found later in images from ATLAS at Mauna Loa. [CBET 49xx, MPEC 2021-N47, 2021 July 8] The comet is at perihelion at 1.4 au in 2021 October and has a period of 9.3 years.
PanSTARRS 1 discovered a 20th magnitude comet in images taken with the 1.8m Ritchey-Chretien on July 20.60. It was identified as a return of 2005 W3 by the MPC. There were prediscovery PanSTARRS observations from 2020 September, October, November and December. The comet was some 13' from the predicted position, corresponding to a delta T of around -1.0 days. [CBET 4506, MPEC 2021-O66, 2021 July 30] At this return the comet is at perihelion at 2.9 au in 2021 September and has a period of 15.9 years. It made a distant encounter (1.1 au) with Saturn in 2014 July.
Marco Micheli recovered 2019 A7 in images taken by other observers with the 8.1m Gemini South telescope on May 17.17. He found confirmatory images of the comet in data from the Canada-France-Hawaii at Mauna Kea taken on June 13. [MPEC 2021-P78, CBET 5010, 2021 August 8] It reaches perihelion in 2023 September.
Marco Micheli recovered 2017 S5 in images taken by other observers with the 8.1m Gemini South telescope on June 9.07. [MPEC 2021-P79, CBET 5011, 2021 August 8]. It reaches perihelion in 2023 March.
Erwin Schwab recovered comet 2014 W12 as a 20th magnitude object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2021 August 16.13. It was a long way from the predicted position, with a delta T of -37.6 days, putting the comet at perihelion in 2021 May rather than June. Hirohisa Sato then reported the comet in images taken on August 7, with Syuichi Nakano then able to find images from the Catalina Sky Survey from 2008 November. There have been no close encounters with any major planets. [MPEC 2021-Q47, CBET 5025, 2021 August 22/23]
In 2020 Sam Deen found images of the comet in DECam data taken with the 4.0m reflector at Cerro Tololo on 2016 January 15.26 and 2016 March 1.14. These were identified by Syuichi Nakano as being a return of 2008 QP20. The comet was close to the expected position. [CBET 4832, 2020 August 17] It was not given a designation for the return, nor was it numbered at the time, though it should have been 410P.
PanSTARRS found a 23rd magnitude image of 2008 QP20 in data taken with the PanSTARRS 1 1.8m Ritchey-Chretien on June 18.59, with additional images from July and August. Despite having been identified at the 2015 return it was given a year identifier. The CBET suggests that it should have been designated as 2016 [A]10 at that return. [MPEC 2021-Q68, 2021 August 28, CBET 5040, 2021 September 18] The comet is at perihelion at 1.8 au in 2022 January and now has a period of 6.7 years following a distant encounter with Jupiter in 2017 July.
Gareth Williams noted on MPEC 2011-A65 [2011 January 14] that it was probable that this was a short-period comet and that further [astrometric] observations of the comet were desirable.
Further observations confirmed the short period orbit, and Hirohisa Sato gave a period of around 5.5 years with perihelion at 1.6 au in 2010 December.
The comet was recovered on 2021 August 20.50 in images taken by the Zwicky Transient Factory with the 1.2m Oschin Schmidt. It was also present in images taken on August 23, 24 and 25. The comet is at perihelion at 1.6 au in December and has a period of 5.5 years. It was some 17' from the predicted position, corresponding to a delta T of +0.79 days. The comet passed 0.41 au from Jupiter in 1986. [MPEC 2021-Q69, CBET 5026, 2021 August 28/31]
Francois Kugel recovered 2015 Q1 in images taken on August 2.96 at his observatory "Chante-Perdrix" (Dauban, France) with his 0.4-m f/2.8 reflector. This was confirmed in follow up observations on August 7 and 16 and by other amateurs Jean-Francois Soulier and John J Maikner. [MPEC 2021-Q75, 2021 August 29, CBET 5038, 2021 September 17] Rob Matson then found prediscovery observations made with the 1.2-m Palomar Schmidt in 2002, but no designation has yet been assigned for that return. The comet passed 0.6 au from Jupiter in 2005 December in an encounter that reduced the perihelion distance, whilst it passed 1.5 au in 2017 December, which increased the perihelion distance. The comet is next at perihelion at 1.8 au in 2022 February and has a period of 6.5 years.
As the orbit improved it became possible to search for earlier observations and PanSTARRS found images of the comet in data taken on 2016 October 25.47 and November 15. It was designated 2016 U2 for this return, though the MPEC does not give elements for that epoch. The CBET confirms the comet name as PanSTARRS. [MPEC 2021-Q96, 2021 August 31, CBET 5041, 2021 September 19]
A paper by Hsieh et al characterises the object as a Main Belt Comet, with activity driven by sublimation around perihelion. They note that archival observations also show activity at the last perihelion in 2016 and estimate a nuclear radius of around 1.6 km. They suggest that it might be a fast rotator.
Erwin Schwab recovered comet 2012 TK8 as a 20th magnitude object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2021 September 30.16. The comet was some 6' from the predicted position, indicating a Delta(T) of -0.38 day. [MPEC 2021-T44, CBET 5048, 2021 October 4] The comet was at perihelion at 3.0 au in 2021 October and now has a period of 8.4 years.
Taras Prystavski recovered 2007 R4 in images taken with the 0.51m iTelescope at Siding Spring on October 24.43. Confirmation came from John Drummond who had imaged the comet on September 5.47. The MPEC gives additional positions from John taken on August 15.61 but does not mention the September observations. The CBET does include these observations, along with additional ones by Filipp Romanov on August 13.61. The comet was some 7' east of the ephemeris position, corresponding to a delta-T of -0.2 days. [MPEC 2021-U108, CBET 5061, 2021 October 27]
Alessandro Odasso identified an object given the minor planet designation of 2020 OV62, found by the Mt Lemmon Survey on 2020 July 31.42, as being a return of 2005 T2. The MPC then found detections by PanSTARRS on 2012 November 5.21 at which return it was given the designation 2012 V5. Sam Deen then found additional PanSTARRS detections from 2012 August, in images taken with the CFH telescope at Mauna Kea in 2013 October and with DECam in 2019 June. The 2012 positions were over a degree from that expected from published predictions. [MPEC 2021-W47, CBET 5073, 2021 November 24/26] The comet will pass 0.40 au from Jupiter in 2037 November, although the 2012 Jupiter MOID was 0.45 au.
Erwin Schwab recovered the comet as a 20th magnitude object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2021 November 30.03. The position was close to that previously predicted, although it was missed at the 2015 return. The MPC then found an isolated tracklet from PanSTARRS 1 from August 8. [MPEC 2021-X81, CBET 5078, 2021 December 3] The comet passed 0.81 au from Jupiter in 2017 October in an encounter that has increased the perihelion distance to 1.85 au. The next close Jupiter encounter is in 2077, when the comet passes within 0.3 au.
The Purple Mountain Observatory discovered a potential 20th magnitude NEO at their XuYi station with their 1.04m Schmidt on 2022 January 11.67. The MPC identified this as a return of 1997 B1 and then found isolated tracklets from 2021 November 29 taken with the Bok 2.25m reflector at Kitt Peak. PanSTARRS then found the comet in images taken earlier in November. This sequence suggests that the comet should have been designated 2022 A2 as this was the discovery. The comet was some 0.5 degrees from the prediction based on observations in 1997. [MPEC 2022 A164, CBET 5091, 2022 January 11/12] The comet is at perihelion at 2.0 au in March and has a period of 25 years. The comet was close to 67P/ in the sky and Nick James subsequently discovered that he had imaged it on January 9, as did Peter Carson.
The MPC identified a 21st magnitude object found in incidental astrometry from Mt Lemmon on January 25.51 and PanSTARRS 2 on February 10.50 as being a return of 2017 R1. [CBET 5100, MPEC 2022-D03, 2022 February 16] The comet is at perihelion at 3.3 au in 2025 September and has a period of 8.4 years.
The comet is one of those suspected to have undergone nuclear splitting according to the list of Marcos & Marcos [Dynamically correlated minor bodies in the outer solar system, MNRAS, 474, 838, 2018 February]. They link it to 208P/McMillan.
Hirohisa Sato recovered 2011 Q3 at 20th magnitude in images taken with the 0.51-m f/6.8 iTelescope astrograph at Siding Spring on 2022 April 5.79, with confirming images taken with the same telescope five days later. [MPEC 2022-H01, CBET 5115, 2022 April 16/19]. The comet is at perihelion at 2.3 au in August. Following the recovery Syuichi Nakano was able to link isolated observations made on 2000 November 28.21 by Spacewatch to the comet. He notes that the comet passed 0.75 au from Jupiter in 1990 and 0.53 au in 2002, in encounters that made changes mostly to the angular elements.
It appeared on the PCCP as 2F61M11 on 2022 June 7.65, so was presumably recovered, though confirmation had to wait a month. Following the recovery additional tracklets from 1998 and 2006 were identified. The comet is at perihelion at 2.4 au in 2022 August and has a period of 8.2 years. [MPEC 2022-N51, CBET 5149, 2022 July 8]
PanSTARRS 2 discovered a new object on June 28.58, which the MPEC automatically identified as a return of 2012 O3. Hirohisa Sato was then able to find the comet in images taken with the 0.51-m f/6.8 iTelescope astrograph at Siding Spring on April 10.80. PanSTARRS checked their images and confirmed that they did show cometary activity. [MPEC 2022-N81, CBET 5150, 2022 July 12]. The comet was at perihelion at 1.6 au in May. It is not clear why the MPEC did not designate the comet as 2022 M2 (or M1) as would be expected from the discovery date.
The comet orbit has a Jupiter MOID of 0.65 au and the comet approached to 0.74 au in 1933 June.
Erwin Schwab recovered comet 2015 X1 at 21st magnitude and essentially stellar, in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2022 August 23.09. Additional confirming observations were made on August 24. Following recovery, Syuichi Nakano was able to link MPC ITF positions from 2008 October 1.38 and 2008 December 31 taken by the Catalina Sky Survey to the comet. [MPEC 2022-Q153, CBET 5164, 2022 August 28]. The comet is at perihelion at 2.1 au in September and has a period of 6.9 years. The comet passed 0.6 au from Jupiter in 2005 January; the orbit has a Jupiter MOID of 0.54 au.
In 2022 October Maik Meyer linked the comet to a comet discovered by Malcolm Hartley on a plate taken on 1987 January 5.73 with the 1.22m Southern Schmidt at Siding Spring. The comet was not found on the plate until March, so there were no follow up observations, and with only one plate the direction of motion was ambiguous so it was given an X/ designtion. Sam Dean was then able to find observations of the comet made with the 3.58m Canada-France-Hawaii telescope on 2013 December 29.30 and 2014 January 3. [MPEC 2022-T74, CBET 5173, 2022 October 5] Logically the comet should now be designated Hartley-Leonard.
B. A. Skiff, Lowell Observatory, reports the discovery of a comet found on CCD images taken by himself on 2004 January 13.27 in the course of the LONEOS program with the 0.59-m Schmidt telescope. The LONEOS images showed stellar appearance, but the motion led Skiff to request that a pair of 5-min R-band CCD exposures be taken of the object by H. R. Miller at the Perkins 1.8-m reflector, and these images show a 3" well- condensed coma and a 12" tail in p.a. 290 deg. To get additional observations, the object's ephemeris was then posted on the NEO Confirmation Page, which resulted in CCD images taken by J. Young (Table Mountain, CA, 0.6-m reflector) on Jan. 13.5 UT that show a 4" coma with a very faint 10" tail in p.a. 262 deg. [IAUC 8267, 2004 January 13]
The comet was finally named in 2004 November: The IAU Committee on Small Bodies Nomenclature has decided to name three comets as follows: C/1996 R3 (Lagerkvist), P/2003 A1 (LINEAR), P/2004 A1 (LONEOS). [IAUC 8430, 2004 November 6]
Charles Schambeau recovered comet 2004 A1 at 25th magnitude in images taken with the 8.1 m Gemini North telescope at Maunakea on 2022 August 21.52. Additional confirming observations were made on August 23. [MPEC 2022-T106, CBET 5178, 2022 October 8]. The comet is at perihelion at 5.5 au in 2027 January and has a period of 22.5 years. The elements by Syuuchi Nakano show that the comet passed 0.031 au from Saturn on 1992 July 30 in an encounter that reduced the perihelion distance from 9.8 au and the period from 43 years. The previous perihelion had been in 1951 October. The comet will approach Jupiter to 0.5 au in 2026 July, with a further small reduction in perihelion distance and period.
Erwin Schwab recovered comet 2007 A2 at 21st magnitude and essentially stellar, in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 2022 September 27.17. Additional confirming observations were made on October 1. [MPEC 2022-T107, CBET 5177, 2022 October 8]. The comet is at perihelion at 2.8 au in November and has a period of 15.9 years.
In October 2022 Michael Kelley reported that 2003 CC22 showed a tail in ZTF images taken on September 27. Sam Dean then noted that images since at least 2018 showed considerable variation in brightness.
Despite this report, the MPC decided to designate it as 2022 B5 based on images taken at Santa Maria de Montmagastrell on 2022 January 28.80. The MPEC also reports that archival ZTF images show cometary activity back to 2022 February. They do not report any of the 2018 observations mentioned by Sam Deen. [MPEC 2022-V36, CBET 5186, 2022 November 2] The comet passed 0.12 au from Saturn in 1938 January and 0.50 au from Jupiter in 1947 June, with more distant passes from Saturn in 1997 September and Jupiter in 2002 September.
Images by several amateurs in 2023 February showed a somewhat elongated and weak central condensation and a tail.
Comet 2017 S9 was recovered at 22nd magnitude in PanSTARRS images taken with the 1.8 m Ritchey-Chretien on 2022 September 2.37. There were earlier PanSTARRS 2 images from August 6. Once recovered, even earlier PanSTARRS images from 2011 August (earliest on August 21.56) and September were found. The prediction based on the 2017 observations required a correction of Delta(T) = -0.69 day. [MPEC 2022-Y14, CBET 5200, 2022 December 17] The comet is at perihelion at 2.2 au in 2023 February and has a period of 5.6 years.
Sam Deen and K Ly later identified images of the comet in archival data from the Canada-France-Hawaii 3.6m telescope on Mauna Kea taken on 2012 August 18, 28, September 12 and 14. It was completely asteroidal and was given the designation 2012 Q3. [CBET 5210, MPEC 2023-B135, 2023 January 27]
In 2023 March K Ly reported finding the comet in images taken with the 8.2m Subaru telescope in 2016 July and August. [MPEC 2023-F99, F100, 2023 March 22]
In 2023 Richard Weryk reported the recovery of 2016 BA14 in images taken in 2020 October (recovery image October 17.52), November, December, and 2021 January from Pan-STARRS 1. [MPEC 2023-G14, CBET 5243, 2023 April 2] The MPEC has a helpful ephemeris to allow you to find the 31st magnitude comet.
Following the discovery, Syuichi Nakano was able to link an asteroid discovered by LONEOS on 2000 July 29.36 and designated 2000 OZ21, but only observed over a five day arc, with the comet. [CBET 5166, 2022 September 3]. It should have been numbered 449, but seemed to have been overlooked; it was eventually numbered in 2023 July.
On 2023 April 16 Rob Matson discovered an object in SWAN images taken between April 5 and 15. Michael Mattiazzo confirmed it with a ground based observation on April 18. Follow up by the amateur community fairly quickly established a link with 2018 HT3, an Apollo asteroid discovered by NEOWISE on 2018 April 22.96. PanSTARRS observations from 2012 September, October and 2013 June were subsequently found. The object was recovered in 2022 November by Spacewatch II. Sam Deen noted that it might be visible in SWAN imagery from 1997 August, 2002 September, 2007 October, 2012 December and 2018 January. It was also visible in STEREO images from 2012 November. The comet was past perihelion but approaching Earth. It was estimated at around 13th magnitude and won't get any brighter but the elongation will improve. It is at high southern declination. This object has not received the 2023 G1 designation as the MPC use a different logic to that used by Brian Marsden who devised the system. In 2023 October Rob Matson checked the SWAN images from 2018 January 16-20 and found the comet, though it was hard to locate being very faint.
Facility astronomers recovered 2008 L2 in images taken with the ESA TBT 0.56-m f/2.52 astrograph at the ESO La Silla Observatory, Chile on June 1.39, with additional images on June 2 and 8. The comet was 19th magnitude and near perihelion. [MPEC 2023-L67, CBET 5270, 2023 June 12/13] The TBT (Test Bed Telescope) is a collaboration between the European Space Agency and the European Southern Observatory to design an autonomous network of telescopes for survey of transients and moving objects. First light was in 2021, and there is a northern component at the Cebreros Satellite Tracking Station in Spain.
The comet is one of those suspected to have undergone nuclear splitting according to the list of Marcos & Marcos [Dynamically correlated minor bodies in the outer solar system, MNRAS, 474, 838, 2018 February]. They link it to 10P/Tempel.
A possible new comet of 19th magnitude was discovered on 2023 June 26.42 in images taken with the 1.5-m reflector of the Mt Lemmon Survey. It was placed on the PCCP as C9DRXC2. Following some confirmatory observations and astrometry, M Suzuki identified it as a return of 2015 T3 some 0.2 degrees from its predicted position, requiring a correction of Delta(T) = +0.58 day to previously published elements. [MPEC 2023-N18, CBET 5277, 2023 July 7]. The comet was at perihelion at 2.2 au in 2023 May and has a period of 8.12 years. The comet passed 0.63 au from Jupiter on 2003 August 24 and will pass 0.28 au from Jupiter on 2025 December 24 in an encounter that will slightly increase the perihelion distance.
The osculation epoch for the orbit is the current standard epoch, rather than the 40-day epoch closest to perihelion, which is normal for comets. Like the recent case of P/2011 P1 (McNaught), P/2010 TO20 (LINEAR-Grauer) has made a recent close approach to Jupiter (0.077 au on 2009 November 2). For current epochs, the perihelion date lies in 2008. For epochs in 2008, the perihelion date lies in 2012-2013.
Marco Micheli and Charles Schambeau recovered comet 2010 TO20 in images taken on 2023 April 20.39 and May 25 with the Gemini South 8.1m reflector. It was 23rd magnitude and had been at perihelion at 5.5 au in 2022 December. Sam Dean had previously found ZTF images from 2009 July. [MPEC 2023-O88, CBET 5283, 2023 July 27] The comet passed 0.24 au from Saturn in 1960 August, 0.35 au from Jupiter on 2003 August 26, and 0.075 au from Jupiter on 2009 October 22. It currently has a period of 14.1 years.
R. H. McNaught, Siding Spring Observatory, reports the discovery of an object on 2004 November 3.40 on images taken by G. J. Garradd with the 0.5-m Uppsala Schmidt telescope in the course of the Siding Spring Survey; McNaught later (November 5 and 6) found the object to be slightly diffuse on CCD images taken with the Siding Spring 1.0-m f/8 reflector. [IAUC 8429, 2004 November 6]
Martin Masek recovered 2004 V3 in images taken on July 19.37 with a 0.3m reflector at the Pierre Auger Observatory, Malargue and then found it in images from July 18. The comet was over 0.5 degrees from the predicted position, requiring a correction of Delta(T) = -3.20 days to the predicted time of perihelion. The comet is fainter than expected, so the light curve may be assymetric. [MPEC 2023-O89, CBET 5282, 2023 July 27]. The comet is at perihelion at 3.9 au in 2023 November and has a period of 19.0 years. It passed 0.27 au from Saturn in 1980 March and 1.03 au from Jupiter in 1986 September.
John Maikner recovered 2014 W1 with the 0.3m telescope at the Comet Hunter Observatory 2 at New Ringgold on 2023 August 2.24, with a confirming image on August 11. Werner Hasubick also imaged it from his Buchloe Observatory on August 14. The MPC have however decided that the recovery observation was made by PanSTARRS on July 30.54. This was found by the MPC in the "isolated tracklet file" and reported as an unidentified object, though it is not clear when this report was made. PanSTARRS then found further images from June 22, 29, July 29 and August 22. The previously published orbit required a correction of Delta(T) = -0.14 day. [MPEC 2023-Q142, CBET 5288, 2023 August 26]
Although some time from perihelion, it is a distant object in a periodic orbit and will initially fade. The period is around 21.2 years and the perihelion distance 3.4 au. Observers contributing to the preliminary orbit include BAA Members Peter Birtwhistle and Stephen Laurie.
An asteroid was discovered at 21st magnitude by Erwin Schwab with the Calar Alto-Schmidt on 2023 September 9.09. JPL classified it as a Centaur. The object was in a 21 year orbit with perihelion at 3.4 au in 2024 July. The orbit has a Jupiter MOID of 0.7 au and a Saturn MOID of 0.3 au. Alessandro Odasso pointed out on October 24 via the comet-ml that the orbit for this object was close to that of 2002 T6 (P/NEAT-LINEAR). The MPC confirmed this on October 30 with the issue of MPEC 2023-U279. Neither this nor CBET 5306 credits Alessandro, although the CBET alludes to the posting leading to further observations.
Given that an orbit was published before the identification was known the comet should have become P/NEAT-LINEAR-Schwab, but this approach was not followed.
Additional astrometry and preliminary parabolic orbital elements (from 25 observations, August 28-29) appear on MPEC 2001-Q70. [IAUC 7698, 2001 August 29] The comet could reach 14th mag at high northern declination in October. This is NEAT's 15th comet and 13th this year.
Additional astrometry orbital elements, published on MPEC 2001-S06, indicate this comet (cf. IAUC 7698) to be of short period, with a period of 23 years. [IAUC 7722, 2001 September 21]
Visual m_1 estimates: September 22.00 UT, 14.0 (K. Sarneczky, Agasvr, Hungary, 0.44-m reflector); October 8.81, 11.8 (R. J. Bouma, Groningen, The Netherlands, 0.31-m reflector); 13.64, 11.9 (K. Yoshimoto, Yamaguchi, Japan, 0.25-m reflector); 14.74, 11.1 (Yoshimoto); 15.85, 11.4 (Bouma). [IAUC 7734, 2001 October 16]
44 observations in 2001/2 give a rather unlikely preliminary uncorrected light curve of 5.5 + 5 log d + 41.0 log r, although this is a poor fit.
Comet 2001 Q6 was recovered at Skygems Chile, Rio Hurtado on 2023 November 29 by Hidetaka Sato. The delta-T correction was -2.7 days compared to the published orbit. The comet passed 0.7 au from Jupiter in 1957 November. It is at perihelion at 1.4 au in 2024 February and has a period of 22 years. On December 9 the MPC posted it on the PCCP as CA06E32 without realising that it had already been recovered. It is a poor return, but if it again brightens rapidly it could reach 13th magnitude. It took the MPC another four days to issue MPEC 2023-X258, with CBET 5325 following.
The MPC then issued another MPEC stating that John Maikner had recovered 2001 Q6 with the 0.3-m telescope at the Comet Hunter Observatory 2 at New Ringgold on December 12.95, with other observers later providing confirming images. The MPC gave a designation of 2023 X5, ignoring the confusion created with designations of 2023 S4 = 2023 X5 for P/Hogan. Until this is resolved I am using X5A for P/NEAT and X5B for P/Hogan. [MPEC 2024-B144, 2024 January 28] This MPEC was later withdrawn [MPEC 2024-B152, 2024 January 29]
In something of a repeat performance the MPC published an orbit for a 22nd magnitude asteroid discovered by PanSTARRS on 2023 November 18.46, with further pre-discovery PanSTARRS images from October 17, 24 and November 12. [MPEC 2023-Y72, 2023 December 21]. Three hours later Maik Meyer put a message on the comets-ml noting that this was actually a return of 2011 NO1. It is not clear whether this will result in a new designation of Elenin-PanSTARRS, or even Elenin-Meyer. The MPC eventually acknowledged the identity in MPEC 2024-B143 [2024 January 28] wrongly atributing Hirohisa Sato as the first to point out the identity. The CBET acknowledge Maik Meyer as being the first to suggest the identity. The previously published elements require a correction of Delta(T) = -0.25 day. [CBET 5339 (wrong elements, 5340, 2024 January 28] The comet is at perihelion in 2024 May at 1.2 au and has a period of 13.3 years. It could reach 14th magnitude around the time of perihelion.
An apparently asteroidal object found by both the Spacewatch and LINEAR projects on CCD images taken on 2004 February 17 has been found to have a 5" centrally condensed coma (of mag R = 18.7) and a 15" tail in p.a. 220-270 deg on CCD images taken on 2004 March 16.3-16.6 by S. S. Sheppard, Y. R. Fernandez, and D. Jewitt with the University of Hawaii 2.2-m reflector. [IAUC 8305, 2004 March 15]
Marco Micheli reported the recovery of 2004 DO29 (P/Spacewatch-LINEAR) in images taken on November 11.24 with the 1.0-m reflector of the ESA Optical Ground Station, Tenerife. Francisco Ocana reported an independent recovery in images taken November 13.22 with the Calar Alto 0.8-m Schmidt.[MPEC 2024-B93, 2024 January 22] The CBET gives a different take on affairs, suggesting that their first indication of the recovery was from Richard Weyrk discovering a new comet in PanSTARRS images from November 25.63, which he linked to 2004 DO29. He then found pre-discovery images from November 11.6. As most of these observations had been kept confidential, Michal Jager made another independent recovery on 2024 January 17.14. The correction to the perihelion time compared to the previous orbit was Delta(T) = -1.50 days. [CBET 5335, 2024 January 23] The comet is at perihelion at 4.1 au in 2024 June and has a period of 19.8 years.
John Maikner recovered 2015 HG16 with the 0.3-m telescope at the Comet Hunter Observatory 2 at New Ringgold on November 17.15, with confirming images two days later. The MPEC states that the recovery images were on November 19 and 20, but the published positions are on November 17 and 19, once again suggesting the proof reading is not a strong point. The previously published orbit required a correction of Delta(T) = 0.5 day. The CBET remarks that the November 17 observations have large residuals and may not be real. They give a recovery date of November 19.15 and also noted that the MPC had found additional ITF observations from December 7, 8 and 16. They also note that supposed observations of the comet made by ATLAS in 2018 July and published by the MPC are almost certainly not of this comet. [MPEC 2024-B134, CBET 5337, 2024 January 26] The comet is at perihelion at 3.1 au in 2024 October and has a period of 10.5 years. It passed 0.066 au from Jupiter in 2006 November, prior to which it had a period of 22 years with perihelion at 4.9 au.
T Oribe recovered 2018 P3 in images taken with the 1.03-m reflector at the Saji Observatory on November 15.39. It was 21st magnitude. The CBET draws attention to observations made in 2013 at Mauna Kea (Published in 2022) and by PanSTARRS (published in 2023), which should have been given a 2013 designation. [MPEC 2024-B135, CBET 5336, 2024 January 26] THe comet was at perihelion at 1.8 au in 2023 December and has a period of 5.2 years.
2017 BQ100 was discovered on 2017/01/28 by PANSTARRS and observed for just 5 days without being recovered. Although I failed to extend the arc, I found further observations from 01/28 by the Dark Energy Camera (W84) which still have not been published showing it with a faint but distinct tail in the antisolar direction. Furthermore, these observations showed that the previous orbit calculating it as a normal main-belt asteroid were due to bad measurements by J43 on 2017/01/29 (consistently about 2-3 arcseconds off) the resultant improved orbit has P=6.96 years and q=2.41 au.It bears vague orbital similarity to 94P/Russell but the orbit is too poor to make any definite claims off of that. I searched in the ITF as well and found no additional observations. It should next come to perihelion in late 2023 or early 2024, at which point the orbit is too poor to attempt any recovery. Times like these make me very much wish that PANSTARRS and Mount Lemmon would make their recent data available, because this comet is definitely somewhere in them.
The ATLAS (Asteroid Terrestrial-impact Last Alert System) team discovered a 19th magnitude comet in images taken with the 0.5 m Schmidt at Sutherland, South Africa on December 18.98. It was posted on the PCCP as A10ZtNK. There were pre-discovery positions from ATLAS Chile from December 13 in an ITF. Richard Weyrk then linked the comet to the previously discovered asteroid 2017 BQ100. This object was discovered by PanSTARRS on 2017 January 28.49. [MPEC 2024-B139, CBET 5338, 2024 January 27]. The comet is at perihelion at 2.4 au in 2024 May and has a period of 7.0 years.
2014 A3 was recovered in incidental PanSTARRS astrometry on December 9.53 and on January 7 and 20. The MPEC and CBET give no clues as to the process of identification. The previously published elements require a correction of Delta(T) = -0.02 day. [MPEC 2024-B170, CBET 5342, 2024 January 31] The comet was at perihelion at 3.5 au in 2023 April and has a period of 9.9 years. It passed 0.071 au from Jupiter in 1971 May and 0.6 au in 2006 September, and 0.7 au from Saturn in 1942 December. Prior to 1971 the perihelion distance was 5.2 au and the period 18.2 years.
Erwin Schwab recovered comet 2012 WA34 at 20th magnitude in images taken with the 1.0-m reflector at the ESA Optical Ground Station at Tenerife on February 12.97. Sam Deen then found images taken on 2023 September 18 and 19 taken with the 4.0-m DECam at Cerro Tololo. [MPEC 2024-D103, CBET 53xx, 2024 February 22]. The comet was at perihelion at 3.1 au in 2023 July and has a period of 10.1 years.
Marco Micheli recovered fragment A of 2016 J1 in images taken with the 8.1-m Gemini North telescope on 2020 December 24.52, and in additional images taken on 2021 February 17, April 11, 14, 15, 17, May 16, 17, 2022 March 13, April 8, 25 and June 19. At recovery the comet was 25th magnitude. [MPEC 2024-E142, CBET 5367, 2024 March 11/13]
Marco Micheli recovered fragment B of 2016 J1 in images taken with the 8.1-m Gemini North telescope on 2021 May 20.28, and in additional images taken on May 30, 31, 2022 June 24 and July 7 and with Gemini South on 2022 July 7. At recovery the comet was 24th magnitude. [MPEC 2024-E143, CBET 5367, 2024 March 11/13] The CBET suggests that the 2021 K5-B designation should not have been made and instead designates it as 2020 Y6-B. It also notes that following recovery and computation of a linked orbit, Syuichi Nakano was able to find images of the comet made on 2004 June 20 by the Catalina Sky Survey. Sam Deen was also able to find additional observations from 2010 and 2011. The splitting likely occured at or after the 2004 return.
To add to the confusion, the MPC published additional observations found by Sam Dean from WISE in 2010 June and by PanSTARRS in 2011 August under the designation 2010 M9. [MPEC 2024-F76, 2024 March 22] Whether this will lead to other cometary returns getting a designation prior to numbering is uncertain.
I am not certain whether the two objects will be given separate numbers, or retain their A and B designations. It may depend on who does the numbering. The answer seems to be that the comet is numbered as 483, and eventually separate orbits for the two components were given.
Erwin Schwab recovered comet 2018 L5 at 21st magnitude in images taken with the 1.0-m reflector at the ESA Optical Ground Station at Tenerife on April 18.o7. He confirmed the recovery with images taken by the Sutherland LCO 1-m Schmidt on April 21. [MPEC 2024-K145, CBET 5400, 2024 May 31]. The comet is at perihelion at 2.3 au in 2025 April and has a period of 6.9 years. It passed 0.4 au from Jupiter in 1978 July and 2014 September. There is a possible identification with 1937 BG
In 2012 November, further observations at Siding Spring showed that it had cometary features and it was reclassified.
Martin Masek recovered 2012 US27 in images taken at the Pierre Auger Observatory with a 0.3m reflector on 2024 July 5.35. He took confirming images the next night, with independent confirmation from Alan Hale on July 12 and Jack Drummond on July 16. With an improved orbit Sam Deen was able to locate the comet in Sloan Digital Sky Survey images taken with the 3.5m telescope at Apache Point on 2002 February 23.4. [MPEC 2024-O57, CBET 5422, 2024 July 26/27]. The comet is at perihelion at 1.8 au in 2024 October and has a period of 11.7 years.
An object discovered by PanSTARRS 2 on 2024 July 9.6 was placed on the PCCP as P21WnsB. This was linked by PanSTARRS to the main belt asteroid discovered in NEAT images and so removed from the PCCP. The discovery object was then subsequently replaced on the PCCP and the linkage removed. MPEC 2024-P23 [2024 August 2] originally had observations of the object with a designation of 2024 N6, but these were edited out. It is not a very transparent process, but a formal MPEC [2024-P41] appeared on August 3. This, along with CBET 5426/7 [August 4] confirmed the linkage, with the latter giving further background on the 2002 return. The comet was at perihelion in 2024 May at 1.7 au and has a period of 7.2 years. It passed 0.4 au from Jupiter in 1991 June and will pass 0.7 au from it in 2026 June.
PanSTARRS 2 recovered 2019 M2 at 22nd magnitude in images taken on 2024 February 4.52, with additional images on February 15, March 1, 31 and April 4. The comet returns to perihelion at 1.07 au in September. The additional astrometry and linked orbit rule out a direct connection with D/Barnard. The comet passed 0.7 au from Jupiter in 1990 January and will pass 0.8 au from the planet in 2037 May. [MPEC 2024-Q25, CBET 5433, 2024 August 20]
PanSTARRS 1 recovered 2014 MG4 at 21st magnitude on May 30.33. Additional images were then found from April 17, 18 and May 7. The comet reaches perihelion at 3.7 au in September. The comet passed 0.05 au from Jupiter in 1955 July, prior to which it was at perihelion at 5.3 au in 1909 July and had a period of 45 years. [MPEC 2024-Q26, CBET 5431, 2024 August 20]
An object appearing on the PCCP as ZTS2139 and discovered on 2024 July 28.48 was linked to a return of 2010 WK and removed from the PCCP on August 2. An MPEC was eventually issued on August 23. This gives the discovery date by the ZTF as July 18.48 when the object was 20th magnitude. It also gives the alternate 2010 designation and the designation for the 2024 return
Martin Masek recovered 2005 SB216 in images taken with the 0.25 m reflector at La Palma on August 30.13, with confirming images taken over the next few days. Subsequently the ZTF reported that they had imaged the comet on August 2, with further images on many subsequent days. [MPEC 2024-R78, CBET 5439, 2024 September 5] The comet is at perihelion at 3.8 au in 2026 January and has a period of 19.2 years. It will pass 0.6 au from Jupiter in 2028 February.
An object of 21st magnitude was discovered on 2024 September 8.30 in images taken with the 1.5-m reflector of the Mt Lemmon Survey. Following further observations it was designated by the MPC as an asteroid. Peter VanWylen and John Maikner pointed out that it could be linked to 2016 A2. Following the linkage, observations were found by T Kobayashi in the MPC "isolated tracklet file" that had been reported as P10hax1 (PanSTARRS) on 2014 December 27.23. [MPEC 2024-U34, CBET 5463, 2024 October 22/23] There is probably some logic as to why it is not now named as Christensen-Lemmon. It is at perihelion at 3.5 au in 2025 October and has a period of 10.4 years. It has a Jupiter MOID of 0.4 au, but there have been no recent close approaches.
Computations by Kenji Muraoka and Hirohisa Sato had quickly suggested that it was a short period object, though the preliminary orbit was parabolic.
The comet was accidently recovered by PanSTARRS on October 7.56 and placed on the PCCP as P120uko. Sam Deen quickly (October 8) spotted that this was a recovery and not a new comet. We wait to see whether it will get a designation for the return and whether it will be numbered. Eventually (October 23) the MPC put out an MPEC, which suggested that the comet had been recovered on September 26.59. This is condradicted by the CBET, which says that the comet was found by PanSTARRS in ITF images taken by Mt Lemmon on September 11.38, with additional PanSTARRS images on September 14.57 and it was these that led to the discovery of the September 26.59 images. The CBET suggests that it was the MPC that then identified it as a return of 2010 A3. [MPEC 2024-U42, CBET 5466, 2024 October 23]. The comet is at perihelion at 1.6 au in 2025 March and has a period of 15.1 years. There will be a distant encounter with Jupiter in 2042 that will reduce the period to 14.5 years and the perihelion distance to 1.5 au. The Jupiter MOID is 0.10 au.
2011 UA134 was accidently recovered in astrometry from Mt Lemmon on 2024 October 5.31 at 21st magnitude, with subsequent astrometry from PanSTARRS on October 9 and 10. [MPEC 2024-U43, CBET 5464, 2024 October 23] The comet is at perihelion at 2.1 au in 2025 February and has a period of 13.3 years.
The MPC finally got round to re-designating it as a comet in 2024 August, following further reports of its cometary nature in 2024 June. There were pre- discovery observations from 2018 March and 2023 April, although the object was then stellar. There appears to have been an initiation of activity between 2023 April 27 and 29. [MPEC 2024-Q04, CBET 5430, 2024 August 16/17]. Despite designating it as a comet, the MPC failed to number it at the next oportunity.
Published by Jonathan Shanklin. Jon Shanklin - jds@ast.cam.ac.uk