Updated 2021 July 30
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 Hirohisa Sato subsequently realised that this was a return of 2007 VQ11 and it was withdrawn from the PCCP.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.
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 has not yet been given a designation for the return, nor has it been numbered, though it should have been 410P.
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.
Published by Jonathan Shanklin. Jon Shanklin - jds@ast.cam.ac.uk