BAA Comet Section : Comets discovered in 2021

Updated 2022 September 20


  • 2014 UN271 (Bernardinelli-Bernstein)
  • 2021 A1 (Leonard)
  • 2021 A2 (NEOWISE)
  • 2021 A3 (414P/STEREO)
  • 2021 A4 (NEOWISE)
  • 2021 A5 (P/PanSTARRS)
  • 2021 A6 (PanSTARRS)
  • 2021 A7 (NEOWISE)
  • 2021 A8 (416P/Scotti)
  • 2021 A9 (PanSTARRS)
  • 2021 A10 (NEOWISE)
  • 2021 A11 (419P/PanSTARRS)
  • 2021 A12 (423P/Lemmon)
  • 2021 B1 (417P/NEOWISE)
  • 2021 B2 (PanSTARRS)
  • 2021 B3 (NEOWISE)
  • 2021 C1 (Rankin)
  • 2021 C2 (P/PanSTARRS)
  • 2021 C3 (Catalina)
  • 2021 C4 (ATLAS)
  • 2021 C5 (PanSTARRS)
  • 2021 C6 (Lemmon)
  • 2021 CT3 [A/PanSTARRS]
  • 2021 D1 (SWAN)
  • 2021 D2 (ZTF)
  • 2021 E1 (420P/Hill)
  • A/2021 E2 (A/Lemmon)
  • 2021 E3 (ZTF)
  • A/2021 E4 (A/Lemmon)
  • 2021 F1 (Lemmon-PanSTARRS)
  • 2021 G1 (Leonard)
  • 2021 G2 (ATLAS)
  • 2021 G3 (PanSTARRS)
  • 2021 HS (P/PanSTARRS)
  • 2021 J1 (Maury-Attard)
  • 2021 J2 (PanSTARRS)
  • 2021 J3 (P/ATLAS)
  • 2021 K1 (ATLAS)
  • 2021 K2 (MASTER)
  • 2021 K3 (Catalina)
  • 2021 K4 (426P/PanSTARRS)
  • 2021 L1 (422P/Christensen)
  • 2021 L2 (P/Leonard)
  • 2021 L3 (Borisov)
  • 2021 L4 (P/PanSTARRS)
  • 2021 L5 (424P/La Sagra)
  • 2021 L6 (427P/ATLAS)
  • 2021 LB18 [A/PanSTARRS]
  • 2021 M1 (429P/LINEAR-Hill)
  • 2021 N1 (P/ZTF)
  • 2021 N2 (P/Fuls)
  • 2021 N3 (PanSTARRS)
  • 2021 N4 (432P/[PanSTARRS])
  • 2021 O1 (Nishimura)
  • 2021 O2 (425P/Kowalski)
  • 2021 O3 (PanSTARRS)
  • 2021 P1 (PanSTARRS)
  • 2021 P2 (PanSTARRS)
  • 2021 P3 (P/PanSTARRS)
  • 2021 P4 (ATLAS)
  • 2021 P5 (431P/Scotti)
  • 2021 Q1 (428P/Gibbs)
  • 2021 Q2 (430P/Scotti)
  • 2021 Q3 (ATLAS)
  • 2021 Q4 (Fuls)
  • 2021 Q5 (P/ATLAS)
  • 2021 Q6 (PanSTARRS)
  • 2021 QM45 (PanSTARRS)
  • 2021 R1 (P/PanSTARRS)
  • 2021 R2 (PanSTARRS)
  • 2021 R3 (P/PanSTARRS)
  • 2021 R4 (P/Wierzchos)
  • 2021 R5 (P/Rankin)
  • 2021 R6 (P/Groeller)
  • 2021 R7 (PanSTARRS)
  • 2021 R8 (P/Sheppard)
  • 2021 R9 (447P/Sheppard-Tholen)
  • 2021 RM114 [A/PanSTARRS]
  • 2021 S1 (ATLAS)
  • 2021 S2 (434P/Tenagra)
  • 2021 S3 (PanSTARRS)
  • 2021 S4 (Tsuchinshan)
  • 2021 T1 (Lemmon)
  • 2021 T2 (Fuls)
  • 2021 T3 (435P/PanSTARRS)
  • 2021 T4 (Lemmon)
  • 2021 U1 (P/Wierzchos)
  • 2021 U2 (436P/Garradd)
  • 2021 U3 (P/Attard-Maury)
  • 2021 U4 (Leonard)
  • 2021 U5 (Catalina)
  • 2021 UL19 [A/Lemmon]
  • 2021 V1 (Rankin)
  • 2021 V2 (P/Fuls)
  • 2021 V3 (437P/PanSTARRS)
  • 2021 W1 (439P/LINEAR)
  • 2021 W2 (440P/Kobayashi)
  • 2021 WT6 [A/Catalina]
  • 2021 X1 (Maury-Attard)
  • A/2021 X2 (A/Kitt Peak)
  • 2021 XZ3 [A/Lemmon]
  • 2021 XS6 [A/Lemmon]
  • 2021 Y1 (ATLAS)
  • 2021 YP [A/Lemmon]

  • 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.

    Observations of comets in 2021 are given in ICQ format. 

    Full details of recently discovered objects will not appear until they are available on the CBAT web pages. The actual accuracy of preliminary orbits is often (nearly always) much worse than the published accuracy implies.  In part this is because each orbital solution is treated as a mathematical construct and does not take account of observational error.  JPL does publish the errors, whereas the MPECs do not.


    2014 UN271 (Bernardinelli-Bernstein)
    Pedro Bernardinelli and Gary Bernstein of the Dark Energy Survey team using the Cerro Tololo 4.0 m reflector discovered a 22nd magnitude asteroid in images taken between 2014 October 20.29 and 2018 November 8.24. Sam Deen was able to find pre-discovery images taken with the CFHT at Mauna Kea on 2014 August 28. It is in a near parabolic, high inclination orbit with perihelion at 10.9 au in 2031 January. [MPEC 2021-M53, CBET 4983 2021 June 19/21]. Luca Buzzi reported that cometary activity was detected on June 22 in images taken with the 0.51 m SkyGems Remote Telescope in Namibia. It was then quickly re-designated as a comet. [MPEC 2021-M83, CBET 4989, 2021 June 24] It is a comet from the inner edge of the Oort cloud and has an absolute magnitude of 2.5, which may translate into a diameter of over 100 km.  It seems to be showing variable activity, with reports of brightening by 0.7 magnitude in less than a day on 2021 September 9. Hubble observations reported by the media suggest a diameter of around 140 km.  An object appeared on the PCCP as A10IfLR in 2022 July which was identified as C/2014 UN71 in the list of previous NEOCP objects, but is presumably this comet, as 2014 UN71 is a main belt asteroid.
    2021 A1 (Leonard)
    Gregory Leonard discovered a comet of 19th magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 January 3.54. It was placed on the PCCP as C4AGJ62. There were prediscovery observations from Catalina Sky Survey (2020 December, 2021 January), Mt Lemmon Survey (2020 April, November), PanSTARRS (2020 April, May, June, August) and the Szeged Asteroid Program, Hungary (2020 November). [CBET 4907, MPEC 2021-A99, 2021 January 10]. The comet was at perihelion at 0.6 au in 2022 January. The comet passed 0.23 au from the earth on 2021 December 12 and 0.0286 au from Venus on 2021 December 18.  Michael Mattizzo noted that it is very dusty and could show strong forward scattering between December  9 and 20.  He also noted that the Earth crossed the orbital plane of the comet on December 8, which could enhance the tail. 

    Michael Mattizzo imaged the comet on October 3, estimating the G magnitude at 13.  JJ Gonzalez observed the comet visually on October 7, estimating it at 11.2. It was reported as being visible in SWAN images in early November 2021. On December 2.3 it was 6.7 in 20x80B from central Cambridge, with a 45' tail.  On December 8.2 it was 5.5 in 8x40B from central Cambridge.  It was on track to reach about 4th magnitude, though some pundits suggested that it was disintegrating.  Some imagers reported the comet being brighter than expected on December 14 and this may be a result of the predicted forward scattering, although there was also a roughly factor of three increase in water vapour production at the same time.  JJ Gonzalez reported it at 3.3 in 10x50B from his mountain location on December 15.75. Observations since then have been a little scattered, with much speculation about outbursts and the comet certainly became much brighter than expected from the light curve.   It is possible that a new active area has come into play. Activity continued to be intermittent, with the comet fading to 4.5 on December 22/23 (Goiato & Gonzalez), but was 3.5 on December 23/24 (Amorim).  Alexandre Amorim reported seeing jets in his 90mm refractor.  Observations continued until January 28, when Chris Wyatt estimated it as 8.5 in his 25cm reflector.  Overall however the comet showed a consistent light curve.

    It was imaged in late February and early March after conjunction, and the images suggest that the comet is disintegrating, with no obvious central condensation.  David Seargent suggests that the disintegration might have already started by late January as his image on January 22 showed the tail more prominent than the head.  An image taken by Nirmal Paul on 2022 March 31 only shows a ghostly outline of the tail.  One contributor to the comet-ml suggests that despite this clear evidence that the comet is no more, it is not disintegrating.  Possibly he means that is because it has already disintegrated.


    2021 A2 (NEOWISE)
    An approximately 15th magnitude comet was discovered from the NEOWISE satellite on 2021 January 3.02. It was posted on the PCCP as N00ht7m. Ground-based observers confirmed the cometary nature, with Michael Mattiazzo reporting it as bright as 12th magnitude in his 0.2 m reflector. [CBET 4908, MPEC 2021-A100, 2021 January 10] It is at perihelion at 1.4 au in 2021 January. A southern circumpolar object at discovery, it is rapidly moving north and could brighten by a further magnitude.  For some reason the MPC leave it un-named in MPEC 2021-B143 [2021 January 31]
    2021 A3 (414P/STEREO)
    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 has not been 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 do use observations from 2016, so it may just be an oversight.  Perhaps because of the delays it also briefly appeared on the PCCP as P11c5Dk.
    2021 A4 (NEOWISE)
    An approximately 20th magnitude comet was discovered from the NEOWISE satellite on 2021 January 3.92. It was posted on the PCCP as N00htdm. The MPEC suggests that it was reported by NEOWISE as being cometary, however the CBET suggests that it was reported because of interesting motion and that ground-based observers confirmed the cometary nature. There were prediscovery observations from PanSTARRS on January 3.6. [CBET 4914, MPEC 2021-A207, 2021 January 15] It is at perihelion at 1.1 au in 2021 March. It appears to be an intrinsically faint object and if so won't come within visual range. Discovery magnitudes of NEOWISE objects are often fainter than seen by visual observers.  Alan Hale reported the comet as being 12.6 on February 6.16.
    2021 A5 (P/PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on January 6.30. It was placed on the PCCP as P11bxkC. There were prediscovery Mt Lemmon observations from 2020 December 16. [CBET 4915, MPEC 2021-A209, 2021 January 15] The comet was at perihelion at 2.6 au in 2020 November and has a period of 5.3 years.
    2021 A6 (PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on January 8.60. It was placed on the PCCP as P11bKhA. There were prediscovery Mt Lemmon observations from 2020 November 26 and December 22. [CBET 4916, MPEC 2021-A210, 2021 January 15] The comet was at perihelion at 7.9 au in 2021 April.
    2021 A7 (NEOWISE)
    An approximately 20th magnitude comet was discovered from the NEOWISE satellite on 2021 January 9.11. It was posted on the PCCP as N00hue0. [CBET 4917, MPEC 2021-A211, 2021 January 15/16] It is at perihelion at 2.0 au in 2021 July.  The CBET suggests that there is a possibility that it may be an intermediate period comet. It was posted as new object A10wPXq on April 29 and again as A10wXnm on May 2, probably as a result of the MPC supplying out of date elements.
    2021 A8 (416P/Scotti)
    Erwin Schwab recovered comet 2013 A2 as a nearly stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on January 14.01. [CBET 4919, MPEC 2021-B21, 2021 January 17]
    2021 A9 (PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on January 12.64. It was placed on the PCCP as P11bX5O. There were prediscovery Mt Lemmon observations from 2020 December 12 and 2021 January 9, and PanSTARRS 2 observations from 2020 December 24.  It may be an intermediate period comet.  [CBET 4922, MPEC 2021-B119, 2021 January 23] The comet is at perihelion at 7.7 au in 2023 November.
    2021 A10 (NEOWISE)
    An approximately 19th magnitude potential NEO was discovered from the NEOWISE satellite on 2021 January 12.16. It was posted on the PCCP as N00hurv. Subsequently astrometrists, including Peter Birtwhistle noted cometary features; Nick James also reported astrometry. [CBET 4930, MPEC 2021-C25, 2021 February 6] It is at perihelion at 1.3 au in 2021 March and has a long period, retrograde orbit. 
    2021 A11 (419P/PanSTARRS)
    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 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].  It is not clear why there was such a long gap between the issue of the CBET and MPEC.
    2021 A12 (423P/Lemmon)
    2008 CL94 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. [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.
    2021 B1 (417P/NEOWISE)
    Erwin Schwab recovered comet 2015 J3 as a nearly stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 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]
    2021 B2 (PanSTARRS)
    PanSTARRS 1 discovered a 20th magnitude comet in images taken with the 1.8m Ritchey-Chretien on January 17.23. It was placed on the PCCP as P11cite. There were prediscovery Catalina Sky Survey observations from 2020 December 12 and PanSTARRS 1 observations from 2020 December 24. [CBET 4921, MPEC 2021-B120, 2021 January 23] The comet is at perihelion at 2.5 au in 2021 May.
    2021 B3 (NEOWISE)
    An approximately 19th magnitude comet was discovered from the NEOWISE satellite on 2021 January 22.25. It was posted on the PCCP as N00hwa7. [CBET 4929, MPEC 2021-C16, 2021 February 4] It is at perihelion at 2.2 au in 2021 March and has a period of around 150 years
    2021 C1 (Rankin)
    David Rankin discovered a comet of 20th magnitude in images taken with the 1.5m reflector on February 11.44 during the Mt Lemmon Survey. It was placed on the PCCP as C4WH682. [CBET 4934, MPEC 2021-D102, 2021 February 24/25]. The comet was at perihelion at 3.5 au in 2020 December.
    2021 C2 (P/PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude comet in images taken with the 1.8m Ritchey-Chretien on February 12.53. It was placed on the PCCP as P11dgUs. There were prediscovery Mt Lemmon observations from 2021 January 17. [CBET 4935, MPEC 2021-D103, 2021 February 24/25] The comet was near perihelion at 4.9 au and has a period of around 30 years.
    2021 C3 (Catalina)
    An object of 19th magnitude was discovered in Catalina Sky Survey images taken with the 0.68m Schmidt on February 7.46. PanSTARRS 1 reported cometary features and it was placed on the PCCP as C1VUXJ1. There were pre-discovery Catalina images from January 16. [MPEC 2021-D112, CBET 4936, 2021 February 26]. The comet was near perihelion at 2.3 au and has a period of around 500 years in a retrograde orbit.
    2021 C4 (ATLAS)
    A 19th magnitude object was discovered in images taken with the 0.5m Schmidt at Haleakala on February 12.61 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team. It was posted on the PCCP as A10vcA4 following reports of signs of cometary activity. [CBET 4937, MPEC 2021-D113, 2021 February 26]. The comet was at perihelion at 4.5 au in 2021 January.
    2021 C5 (PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on February 12.35. It was placed on the PCCP as P11dcTx. There were prediscovery PanSTARRS observations from 2020 December 22 2021 January 23 and February 6 and Mt Lemmon observations from 2021 January 18. [CBET 4941, MPEC 2021-E64, 2021 March 8] The comet is at perihelion at 3.2 au in 2023 February.
    2021 C6 (Lemmon)
    The Mt Lemmon Survey discovered a potential NEO of 21st magnitude in images taken with the 1.5m reflector on February 7.43. It was placed on the PCCP as C4V28F2. Confirmation astrometry showed cometary features and pre-discovery images from PanSTARRS were found from January 23. [CBET 4946, MPEC 2021-F63, 2021 March 21]. The comet is at perihelion at 3.3 au in 2021 November. It is in a hyperbolic retrograde orbit.
    2021 CT3 [A/PanSTARRS]
    PanSTARRS 1 discovered an asteroid in images taken with the 1.8m Ritchey-Chretien on 2021 February 7.37. The object, classified by JPL as a Centaur, is at perihelion at 4.3 au in 2021 December and is in a retrograde orbit with a period of around 20 years. It briefly appeared on the PCCP as P11czUb.
    2021 D1 (SWAN)
    Michael Mattiazzo discovered a comet on February 25 in SWAN images taken since February 19 and this was confirmed in ground based images taken by Michael Jaeger on February 28.  The comet is currently poorly placed for visual observation, but is imageable.  The comet was near perihelion at 0.9 au and will fade.  Nick James, Denis Buczynski, Werner Hasubick and Richard Miles all made confirmatory images and astrometery of the comet. The MPC published an orbit and designated the comet in MPEC 2021-E19 [2021 March 4]. This gave an orbit with a period of around 75 years. CBET 4939 appeared five hours later on March 5 and gave a parabolic orbit based on a shorter arc with fewer observations, though with much more detail about the confirming observations.
    2021 D2 (ZTF)
    The Zwicky Transient Facility reported observations of a 19th magnitude possible NEO made on February 19.55 with the 1.2m Oschin Schmidt. This was placed on the PCCP as ZTF0KcP and subsequently found to show cometary features by astrometrists.  The CBET note that it is the same object as ZTF0Kii reported on March 13.7  [CBET 4947, 4948 (a correction), MPEC 2021-F67, 2021 March 22]. The comet is at perihelion at 2.9 au in 2022 February.
    2021 E1 (420P/Hill)
    Erwin Schwab recovered comet 2009 Q1 as a stellar object in images taken with the 0.8-m f/3 Schmidt reflector at Calar Alto, Spain, on 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]
    2021 E2 (A/Lemmon)
    The Mt Lemmon Survey discovered an object of 21st magnitude in images taken with the 1.5m reflector on March 7.39. It was placed on the PCCP as C4ZL362. No evidence for cometary activity has been detected and the object has passed perihelion. [MPEC 2021-H143, 2021 April 28]. The object was at perihelion at 2.3 au in 2020 December. It is in a long-period retrograde orbit.
    2021 E3 (ZTF)
    The Zwicky Transient Facility reported observations of a 20th magnitude possible NEO made on March 9.53 with the 1.2m Oschin Schmidt. This was placed on the PCCP as ZTF0Kij and subsequently found to show cometary features by astrometrists.  [CBET 4960, MPEC 2021-J71, 2021 May 6/7]. The comet is at perihelion at 1.8 au in 2022 June.  Marco Goiato observed it on April 30, when it was already 11.4 in his 0.22m reflector.  It could brighten by a further magnitude by the time of perihelion when it will be at high southern declination.  
    2021 E4 (A/Lemmon)
    The Mt Lemmon Survey discovered an object of 21st magnitude in images taken with the 1.5m reflector on March 7.32. It was placed on the PCCP as C5DDQL2. There were pre-discovery images from PanSTARRS in 2020 December, 2021 January and February. No evidence for cometary activity has been detected but the object has not yet passed perihelion. [MPEC 2021-M78, 2021 June 23]. The object is at perihelion at 4.7 au in 2022 April. It is in a long-period retrograde orbit.
    2021 F1 (Lemmon-PanSTARRS)
    PanSTARRS 1 discovered an asteroid in images taken with the 1.8m Ritchey-Chretien on 2021 March 19.41. It was placed on the PCCP as P11e2jE. There were fractionally earlier observations from Mt Lemmon. [MPEC 2021-H142, 2021 April 27] The object is at perihelion at 1.0 au in 2022 April and is in a retrograde orbit. It showed cometary activity as it approached perihelion.  Alan Hale reported detecting clear cometary activity on 2022 January 28, with a total magnitude of around 13.  Somewhat belatedly, MPEC 2022-C15 and CBET 5095 were issued on February 2, reporting that cometary activity had been detected as early as 2021 December 1 by Hirohisa Sato.  Unfortunately it is a poor return with the object being in conjunction on the opposite side of the Sun at perihelion.  It may brighten to 10th magnitude.
    2021 G1 (Leonard)
    Gregory Leonard discovered a comet of 21st magnitude in images taken with the 1.5 m reflector of the Mt Lemmon Survey on 2021 April 11.33. It was placed on the PCCP as C5EEGT2. [CBET 4959, MPEC 2021-J72, 2021 May 6]. The comet is at perihelion at 3.4 au in 2021 July and is in a long period orbit.  It passed 0.5 au from Saturn in 2018 March.
    2021 G2 (ATLAS)
    A 19th magnitude object was discovered by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team in images taken with the 0.5m Schmidt at Mauna Loa on April 11.25. It was posted on the PCCP as A10wotD. No cometary activity was detected (by professional observers) at the time. [MPEC 2021-M79, 2021 June 23]. The object is at perihelion at 5.0 au in 2024 September. CBET 4988 [2021 June 24] suggests that cometary activity has been detected and the object is probably a comet. Professional observers finally reported a coma on September 29 and it was then redesignated as a comet.  The comet's orbit shows non-gravitational influences.  [MPEC 2021-T206, CBET 5057, 2021 October 11]
    2021 G3 (PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude potential NEO in images taken with the 1.8m Ritchey-Chretien on April 1.26. With the PanSTARRS group finding signs of cometary activity it was placed on the PCCP as P11ebKr. There were prediscovery Mt Lemmon observations from 2021 February and Catalina Sky Survey observations using the Kitt Peak Bok telescope in March. [CBET 4990, MPEC 2021-M86, 2021 June 25] The comet is at perihelion at 5.2 au in 2021 October.
    2021 HS (P/PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude asteroid in images taken with the 1.8m Ritchey-Chretien on April 16.37. There were prediscovery PanSTARRS 2 observations from six days earlier. An orbit was published in MPEC 2021-H60 [2021 April 18]. On July 6 [The MPEC says July 7, but reports observations for July 6], Hirohisa Sato reported detecting a coma, which was soon confirmed by Luca Buzzi. It wasn't until further observations were made in September that a discovery MPEC was issued. [MPEC 2021-S44, CBET 5043, 2021 September 19/20] The comet was at perihelion at 0.8 au in 2021 August. The comet passed 0.26 au from Earth on August 13, and around 0.3 au from Jupiter in 1954 August. The CBET notes that the light-curve is somewhat unusual with a small K1 value.
    2021 J1 (Maury-Attard)
    Alain Maury and Georges Attard discovered a comet of 19th magnitude in images taken with the 0.28 m Schmidt of the MAP Observatory, San Pedro de Atacama, Chile (W94) on 2021 May 9.33. It was placed on the PCCP as 1581K01. [CBET 4972, MPEC 2021-K11, 2021 June 2]. The comet was at perihelion at 1.7 au in 2021 February and has a period of around 130 years. The MAP observatory is named for the initial letters of the last names of the amateur astronomers Alain Maury, Georges Attard and Daniel Parrot who own and run the observatory, which is dedicated to finding new asteroids and comets.   The discovery is eligible for the Edgar Wilson Award.
    2021 J2 (PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude comet in images taken with the 1.8m Ritchey-Chretien on May 10.41. It was placed on the PCCP as P11g7TN. There were prediscovery PanSTARRS observations from 2021 March, April and May and Mt Lemmon observations from earlier on May 10. [CBET 4973, MPEC 2021-L24, 2021 June 2] The comet is at perihelion at 4.7 au in 2021 September.
    2021 J3 (P/ATLAS)
    A 19th magnitude object was discovered in images taken with the 0.5m Schmidt at Haleakala on May 13.55 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team. It was posted on the PCCP as A10xbi7 following reports of signs of cometary activity in follow up images (and subsequently given as 2021 A3 on the list of previous NEO confirmations). [CBET 49xx, MPEC 2021-L26, 2021 June 3]. The comet was at perihelion at 4.9 au in 2019 June and has a period of around 25 years.
    2021 K1 (ATLAS)
    A 17th magnitude object was discovered in images taken with the 0.5m Schmidt at Haleakala on May 24.61 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team. It was posted on the PCCP as A10xB7g with an earlier discovery date of May 14.59 as this had been submitted to the MPC as an isolated tracklet. There were many PanSTARRS pre-discovery observations back to 2020 April. [CBET 4968, MPEC 2021-K89, 2021 May 27]. The comet was at perihelion at 2.5 au in 2021 May and has a period of around 45 years.
    2021 K2 (MASTER)
    The MASTER team reported the discovery of a 19th magnitude comet found using the MASTER (Mobile Astronomical System of the Telescope-Robots) auto detection system with the robotic 0.4m f/2.5 reflector at the SAAO, Sutherland, South Africa on May 22.98, with prediscovery images from earlier in May. It was confirmed by other observers. [CBET 4975, MPEC 2021-L89, 2021 June 9]. The comet will reach perihelion at 5.5 au in 2021 August. 
    2021 K3 (Catalina)
    A potential NEO of 22nd magnitude was discovered in Catalina Sky Survey images taken with the 2.25 m Bok telescope at Kitt Peak on May 20.42. PanSTARRS 1 reported cometary features and it was placed on the PCCP as C076EZ5. [MPEC 2021-M87, CBET 4991, 2021 June 25]. The comet is at perihelion at 5.2 au in 2022 February.
    2021 K4 (426P/PanSTARRS)
    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.
    2021 L1 (422P/Christensen)
    Cristovao Jacques recovered comet 2006 S4 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]
    2021 L2 (P/Leonard)
    Gregory Leonard discovered a comet of 20th magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 June 8.40. It was placed on the PCCP as C5QPCV2. There were prediscovery observations from the Mt Lemmon Survey and PanSTARRS in 2021 May. [CBET 4984, MPEC 2021-M74, 2021 June 22]. The comet is at perihelion at 1.9 au in 2021 July and has a period of 8.2 years.
    2021 L3 (Borisov)
    Gennady Borisov discovered an 20th magnitude comet in images taken with the MARGO 0.65-m f/1.5 astrograph at Nauchnij, Crimea on June 8.91. It was placed on the PCCP as gb00279 and quickly confirmed by other astrometrists. [CBET 4885, MPEC 2021-M75, 2021 June 22] The comet is at perihelion at 8.4 au in 2022 March.   The discovery is eligible for the Edgar Wilson Award.
    2021 L4 (P/PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on June 14.27. It was placed on the PCCP as P11h3rz. There were prediscovery Spacewatch and PanSTARRS observations from earlier in the month. [CBET 4986, MPEC 2021-M77, 2021 June 23] The comet was at perihelion at 2.8 au in 2019 September and has a period of 5.6 years. Given the long time since perihelion it might be in outburst.
    2021 L5 (424P/La Sagra)
    Images of 2012 S2 were found in incidental PanSTARRS 1 asrometry taken with the 1.8m Ritchey-Chretien on June 6.53. It was independently found later in images from ATLAS at Mauna Loa. [CBET 4994, 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.
    2021 L6 (427P/ATLAS)
    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.
    2021 LB18 [A/PanSTARRS]
    PanSTARRS 1 discovered an asteroid in images taken with the 1.8m Ritchey-Chretien on 2021 June 7.48. The object, classified by JPL as a Centaur, was at perihelion at 3.4 au in 2021 March and is in a retrograde orbit with a period of around 130 years. It appeared on the PCCP as P11gO7R. [MPEC 2021-M97, 2021 June 28]
    2021 M1 (429P/LINEAR-Hill)
    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 has a period of 6.7 years.
    2021 N1 (P/ZTF)
    The Zwicky Transient Facility reported observations of a 19th magnitude comet made on July 2.46 with the 1.2m Oschin Schmidt. This was placed on the PCCP as ZTF0LHw. [CBET 4999, MPEC 2021-N115, 2021 July 13]. The comet was at perihelion at 1.0 au in 2021 June and has a period of around 5.1 years. 
    2021 N2 (P/Fuls)
    David Carson Fuls discovered an 18th magnitude comet in Catalina Sky Survey images taken with the 0.68-m Schmidt on July 9.44. It was placed on the PCCP as C266K41. There were pre-discovery Catalina images from June 27. [MPEC 2021-N137, CBET 5000, 2021 July 15/16]. The comet is at perihelion at 3.8 au in 2021 November and has a period of around 18 years.  It passed within 0.4 au of Saturn in 2014 September and will do so again in 2102.
    2021 N3 (PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude comet in images taken with the 1.8m Ritchey-Chretien on July 13.52. It was placed on the PCCP as P11iNI. There were prediscovery PanSTARRS observations from 2021 June and July. [CBET 5003, MPEC 2021-O39, 2021 July 22/23] The comet was at perihelion at 5.7 au in 2020 August and may have a period of around 2000 years.
    2021 N4 (432P/PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude comet in images taken with the 1.8m Ritchey-Chretien on August 9.57 It was placed on the PCCP as P11iUGx. It was then linked to an object in incidental astrometry taken by PanSTARRS on July 8.53. [MPEC 2021-Q01, CBET 5019, 2021 August 16]. The comet is near perihelion at 2.3 au and has a period of 5.3 years. It has not yet been officially named, as the preliminary orbit is similar to that of a main belt asteroid.

    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]


    2021 O1 (Nishimura)
    Japanese amateur Hideo Nishimura from Gansho-ji, Kakegawa discovered a comet with a digital camera (Canon EOS 6D + 200mm telephoto lens) on July 21.78. He originally thought that it might be an outburst of 8P/Tuttle.  Michael Jäger was amongst those confirming the object and he gives a total magnitude of 9.2. It was placed on the PCCP as HN002. [MPEC 2021-O47, CBET 5004, 2021 July 25]. The comet is at perihelion at 0.8 au in August. Unfortunately this timing is nearly as bad as it could be, putting the comet on the far side of the Sun and at poor elongation. The comet has been at less than 30 degrees elongation since February, which probably explains why it was not picked up previously by search programmes.   The discovery is eligible for the Edgar Wilson Award.
    2021 O2 (425P/Kowalski)
    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] 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.
    2021 O3 (PanSTARRS)
    PanSTARRS 1 discovered a 20th magnitude comet in images taken with the 1.8m Ritchey-Chretien on July 26.48. It was placed on the PCCP as P11ibiE. [CBET 5009, MPEC 2021-P05, 2021 August 1/2] The comet was at perihelion at 0.3 au in 2022 April. The initial observations suggested a fairly faint absolute magnitude, and it only just survived perihelion. 

    The comet was reported on comets-ml as being 7th-8th magnitude in SWAN images on April 7 and 9, however Michael Mattiazzo imaged the area of the comet on April 22 and could see nothing convinving down to a stellar magnitude of 9.  SWAN saw something more akin to a debris cloud.  Other imagers suggested that it was around 9th magnitude in late April.  STEREO images suggested that only a debris train remained, with no discernable condensation.  In early May imagers captured the debris, estimating a total magnitude of around 14, much fainter than expected if it was still active.  Images in mid May did however show a weak condensation of around 13th magnitude. 


    2021 P1 (PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude comet in images taken with the 1.8m Ritchey-Chretien on August 9.51. It was placed on the PCCP as P11iUcP. There were prediscovery PanSTARRS observations from 2021 July and August, with the August 4.56 observations having been submitted in incidental astrometry. [MPEC 2021-Q02, CBET 5003, 2021 August 16] The comet is at perihelion at 4.4 au in 2022 June. Although the circumstances seem similar to those of 2021 N4, this time the comet has received a name.
    2021 P2 (PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude object in images taken with the 1.8m Ritchey-Chretien on August 7.52, which further PanSTARRS astrometry showed as cometary. It was placed on the PCCP as P11iIYn. There were prediscovery PanSTARRS observations from 2021 June. [MPEC 2021-Q28, CBET 5021, 2021 August 18/19] The comet is at perihelion at 5.1 au in 2023 January and is in a retrograde orbit according to the MPEC and JPL.  The CBET originally gave a rather different orbit, with perihelion at 4.4 au in 2022 June and in a prograde direction.  This appeared to be indentical to that for 2021 P1, and a correction to the CBET was duly issued [CBET 5023, 2021 August 20].
    2021 P3 (P/PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on August 11.58. It was placed on the PCCP as P11j2nn. There were prediscovery PanSTARRS observations from earlier in August. [MPEC 2021-Q29, CBET 5022, 2021 August 19/20] The comet was at perihelion at 2.9 au in 2021 May and has a period of around 9 years.
    2021 P4 (ATLAS)
    A 19th magnitude object was discovered in images taken by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team with the 0.5m Schmidt at Haleakala on August 10.54. It was posted on the NEOCP as A10zRkH and with follow-up astrometry showing cometary activity it was transferred to the PCCP. [MPEC 2021-Q42, CBET 5024, 2021 August 21]. The comet is at perihelion at 1.1 au in 2022 July and is in a 2000 year period orbit. Unfortunately, although the earth MOID is only 0.09 au, it is a poor return and the comet will only reach 11th magnitude at perihelion whilst at a low solar elongation.
    2021 P5 (431P/Scotti)
    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.
    2021 Q1 (428P/Gibbs)
    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 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 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]
    2021 Q2 (430P/Scotti)
    2011 A2 was recovered on 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]
    2021 Q3 (ATLAS)
    A 19th magnitude object was discovered in images taken by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team with the 0.5m Schmidt at Haleakala on August 26.30. It was posted on the NEOCP as A10AraK and when PanSTARRS reported cometary activity it was transferred to the PCCP. PanSTARRS also made a pre-discovery observation on August 19. [MPEC 2021-Q97, CBET 5027, 2021 August 31/32]. The comet is at perihelion at 5.2 au in 2022 January and is in a 600 year periodic orbit.  The CBET originally prefered a parabolic orbit, which gave perihelion as 2021 November at 5.4 au.
    2021 Q4 (Fuls)
    David Carson Fuls discovered a comet of 20th magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 August 26.30. It was placed on the PCCP as C5TP1J2. Pre-discovery PanSTARRS 1 and 2 images dating back to 2020 April were quickly found. [MPEC 2021-Q102, CBET 5028, 2021 August 31/33]. The comet is a distant one, reaching perihelion at 7.6 au in 2023 June.
    2021 Q5 (P/ATLAS)
    A 17th magnitude comet was discovered in images taken by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team with the 0.5m Schmidt at Haleakala on August 29.61. It was posted on the PCCP as A10ACD6. [MPEC 2021-R98, CBET 5029, 2021 September 6]. The initial orbit is still a little uncertain, but suggests that the comet was at perihelion at 1.2 au in late August and is in a 6 year periodic orbit. This suggests that the comet made a close pass to Jupiter in 2019 February.  Sam Deen has calculated a new orbit using additional astrometry, which suggests that the comet passed 0.07 au from Jupiter.  The pre-encounter orbit had perihelion at 2.6 au and an eight year period.  The comet will again encounter Jupiter in 2030, which will increase the perihelion distance.  JJ Gonzalez observed it at around 12th magnitude whilst it was still on the PCCP, suggesting that it is brighter than the quoted discovery magnitude, as is often the case.
    2021 Q6 (PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude comet in images taken with the 1.8m Ritchey-Chretien on August 22.52. It was placed on the PCCP as P11jupO. There were prediscovery PanSTARRS 1 observations from 2021 January, July and August. [MPEC 2021-R167, CBET 5032, 2021 September 9] The comet is at perihelion at 8.7 au in 2024 March.
    2021 QM45 (PanSTARRS)
    PanSTARRS 1 discovered a 22nd magnitude asteroid in images taken with the 1.8m Ritchey-Chretien on August 17.51. There were prediscovery PanSTARRS 1 observations from earlier in August. Images taken by the Palomar Mountain ZTF on 2022 June 29 and 30 showed cometary features, when analysed by automatic detection software and it was reported as a possible new comet. PanSTARRS then looked at archival images and also noted cometary features in 2021 October. [MPEC 2021-N12, CBET 5145, 2022 July 2] The comet is at perihelion at 2.8 au in 2022 August.
    2021 R1 (P/PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on September 4.36. It was placed on the PCCP as P11k2mj. There were prediscovery PanSTARRS 1 observations from 2020 August, September, 2021 July and August, with PanSTARRS 2 observations from 2020 September. [MPEC 2021-R150, CBET 5030, 2021 September 8] The comet is at perihelion at 4.9 au in 2021 December and has a period of around 25 years.
    2021 R2 (PanSTARRS)
    PanSTARRS 2 [The MPEC says PanSTARRS 1, but this is clearly an error] discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on September 5.34. It was placed on the PCCP as P221kcz3. There were prediscovery PanSTARRS 1 observations from 2021 August and September. [MPEC 2021-R151, CBET 5031, 2021 September 8] The comet is at perihelion at 7.3 au in 2021 December.
    2021 R3 (P/PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude object in images taken with the 1.8m Ritchey-Chretien on September 5.32, which was placed on the NEOCP as P11kcfu. Michael Jaeger reported cometary activity and it was moved to the PCCP. There were prediscovery PanSTARRS 1 observations from 2021 July and August, with PanSTARRS 2 observations from 2021 August. [MPEC 2021-R255, CBET 5033, 5036, 2021 September 11/12] The comet was at perihelion at 2.5 au in 2021 May and has a period of around 7.3 years. It passed 0.4 au from Jupiter in 2002 September.
    2021 R4 (P/Wierzchos)
    Kacper W Wierzchos discovered a comet of 21st magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 September 6.40. It was placed on the PCCP as C5U2GG2. There were pre-discovery PanSTARRS 2 images from a couple of days earlier. [MPEC 2021-R256, CBET 5034, 2021 September 11/12]. The comet is at perihelion at 2.3 au in 2021 October and has a period of around 13 years.
    2021 R5 (P/Rankin)
    David Rankin discovered a comet of 19th magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 September 9.29. It was placed on the PCCP as C5V8842. There were pre-discovery PanSTARRS 1 images from 2021 June and August, and ATLAS and PanSTARRS 2 images from earlier in September. [MPEC 2021-R257, CBET 5035, 2021 September 11/12]. The comet is at perihelion at 3.3 au in 2022 January and has a period of around 11 years.  The comet passed 0.5 au from Jupiter in 2007 August and a little further away in 2019 April.
    2021 R6 (P/Groeller)
    Hannes Groeller discovered a comet of 20th magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 September 12.46. It was placed on the PCCP as C5XUMT2. There were pre-discovery PanSTARRS 2 images from 2021 August and PanSTARRS 1 images from earlier in September. [MPEC 2021-S113, CBET 5045, 2021 September 28]. The comet is at perihelion at 2.6 au in 2021 October and has a period of around 16 years.
    2021 R7 (PanSTARRS)
    PanSTARRS 2 discovered a 22nd magnitude NEO candidate in images taken with the 1.8m Ritchey-Chretien on September 5.43. It was placed on the NEOCP as P221kcLa. PanSTARRS follow up observations with the CFHT showed it as cometary, as did other astrometrists. There were prediscovery PanSTARRS 1 observations from 2021 August 7. [MPEC 2021-T162, CBET 5050, 2021 October 8] The comet was at perihelion at 5.6 au in 2021 April.
    2021 R8 (P/Sheppard)
    Scott Sheppard discovered a 22nd magnitude comet in images taken with the "Hyper Suprime-Cam" CCD on the 8.2-m f/2.2 Subaru reflector at Mauna Kea on September 5.55. After the discovery PanSTARRS was asked to search archival imagery and found images of the comet from August and early in September. It was placed on the PCCP as i249429. [MPEC 2021-X149, CBET 5079, 2021 December 7] The comet was at perihelion at 2.1 au in October and has a period of 5.2 years.
    2021 R9 (447P/Sheppard-Tholen)
    In 2022 July Scott Sheppard and David Tholen discovered a 22nd magnitude comet in images taken with the "Hyper Suprime-Cam" CCD on the 8.2-m f/2.2 Subaru reflector at Mauna Kea on 2021 September 5.62. After the discovery PanSTARRS was asked to search archival imagery and found images of the comet from 2021 June to 2022 January. It was placed on the PCCP as g293400. After the astrometry was published Syuichi Nakano found isolated tracklets from 2008 October from Mt Lemmon and Sam Deen found an image from 2007 June taken with the CFH 3.6-m reflector. [MPEC 2022-O19, CBET 5152, 2022 July 22] The comet is at perihelion at 4.6 au in August and currently has a period of 13.4 years. It passed 0.45 au from Jupiter in 1931 January and will pass a similar distance in 2037 March, though the encounters do not make drastic changes to the orbit.
    2021 RM114 [A/PanSTARRS]
    PanSTARRS 1 discovered a 23rd magnitude object in images taken with the 1.8m Ritchey-Chretien on September 13.34. It was placed on the NEOCP as P11l6d7. There were prediscovery PanSTARRS 1 observations from 2021 August 9 and September 7. [MPEC 2021-U56, 2021 October 22] The object is in a long period retrograde orbit taking over 1000 years and is at perihelion at 4.0 au in 2022 January. JPL classify it as a Trans-Neptunian Object. No cometary activity has been detected to date.
    2021 S1 (ATLAS)
    An 18th magnitude comet was discovered in images taken with the 0.5m Schmidt at Haleakala on September 27.57 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team. It was posted on the PCCP as A10BpPq. [MPEC 2021-T21, CBET 5047, 2021 October 3]. The comet is at perihelion at 6.1 au in 2022 March.
    2021 S2 (434P/Tenagra)
    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 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 is at perihelion at 3.0 au in 2021 October and currently has a period of 8.4 years.
    2021 S3 (PanSTARRS)
    PanSTARRS 2 discovered a 20th magnitude comet in images taken with the 1.8m Ritchey-Chretien on September 24.56. It was placed on the PCCP as P221lhTi. [MPEC 2021-T166, CBET 5051, 2021 October 8] The comet is at perihelion at 1.3 au in 2024 February, though there is an uncertainty of 10 days in the date of perihelion and 0.02 au in the perihelion distance. The comet could come into visual range in the middle of 2023 and reach about 7th magnitude around the time of perihelion. UK observers should be able to pick it up from mid February 2024, but it is a morning object when brightest.
    2021 S4 (Tsuchinshan)
    The Purple Mountain Observatory discovered a potential NEO with the 1.04-m f/1.8 Schmidt on September 29.77. Roberto Haver and R. Gorelli reported cometary activity in images taken at the Frasso Sabino observatory with a 0.37-m f/6.70 Cassegrain on October 2.  There were pre-discovery PanSTARRS 2 and 1, and Mt Lemmon images from earlier in September. [MPEC 2021-T167, CBET 5052, 2021 October 8]. The comet is at perihelion at 6.7 au in 2023 December.
    2021 T1 (Lemmon)
    The Mt Lemmon Survey discovered an object of 20th magnitude in images taken with the 1.5m reflector on October 2.21. It was placed on the NEOCP as C60DRY2. Roberto Haver and R. Gorelli reported cometary activity in images taken at the Frasso Sabino observatory with a 0.37-m f/6.70 Cassegrain on October 2.9. There were pre-discovery images from the Catalina Sky Survey in 2021 September. [MPEC 2021-T168, CBET 5053, 2021 October 8/9]. The comet was near perihelion at 3.1 au.
    2021 T2 (Fuls)
    David Carson Fuls discovered a 20th magnitude comet in Mt Lemmon Survey images taken with the 1.5m reflector on October 2.38. It was placed on the PCCP as C60E7J2. [MPEC 2021-T169, CBET 5054, 2021 October 8/9]. The comet is at perihelion at 1.3 au in 2022 June. Unfortunately the circumstances are poor and the comet may only reach 13th magnitude.
    2021 T3 (435P/PanSTARRS)
    PanSTARRS 1 discovered a 20th magnitude comet in images taken with the 1.8m Ritchey-Chretien on October 2.40. It was placed on the PCCP as P11lWkH and pre-discovery PanSTARRS observations were quickly found, first PanSTARRS 1 and 2 observations from 2020 April and May, then PanSTARRS 1 observations from the previous return between 2015 and 2017 for which it was given the designation 2015 K6. [The MPC seem to have developed a convention whereby a comet can be designated at one previous pre-discovery apparition and that it is the first reported one.] Sam Deen then found DECam images from 2015 February and Sloan Digital Sky Survey images from 2002 January. [MPEC 2021-T184, CBET 5056, 2021 October 9] The comet was at perihelion at 2.1 au in 2021 July.
    2021 T4 (Lemmon)
    The Mt Lemmon Survey discovered an object of 20th magnitude in images taken with the 1.5m reflector on October 7.35. It was placed on the NEOCP as C6131F2. Erik Bryssinck reported cometary activity in images taken with the Telescope Live 0.61-m reflector at El Sauce Observatory, Rio Hurtado, Chile on October 11.4. There were pre-discovery images from PanSTARRS 1 in August, PanSTARRS 2 and Mt Lemmon in September and PanSTARRS 1 in October. [MPEC 2021-U187, CBET 5063, 2021 October 29]. The comet does not reach perihelion, which is at 1.4 au, until 2023 July. The comet passes 0.5 au from the Earth 11 days before perihelion. The comet could reach 8th magnitude, but will be at high southern declination and not visible from the UK when brighter than 12th magnitude.
    2021 U1 (P/Wierzchos)
    Kacper W Wierzchos discovered a comet of 19th magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 October 18.35. It was placed on the PCCP as C69C5G2. There were pre-discovery PanSTARRS 1 and 2 images from September and PanSTARRS 2, Mt Lemmon and Catalina images from earlier in October. [MPEC 2021-U43, CBET 5058, 2021 October 19/20]. The comet is at perihelion at 2.4 au in 2021 September and has a period of around 25 years.
    2021 U2 (436P/Garradd)
    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]
    2021 U3 (P/Attard-Maury)
    Alain Maury and Georges Attard discovered a second comet, of 19th magnitude, in images taken with the 0.28 m Schmidt of the MAP Observatory, San Pedro de Atacama, Chile (W94) on 2021 October 24.31. It was placed on the PCCP as 1AN2E11. They confirmed the cometary nature with observations made with the 0.40 m reflector at the nearby Observatorio Panameno the following night. [CBET 5064, MPEC 2021-V21, 2021 November 2]. The comet was at perihelion at 1.9 au and has a period of 8.6 years. The comet passed 0.5 au from Jupiter in 2019 April. The MAP observatory is named for the initial letters of the last names of the amateur astronomers Alain Maury, Georges Attard and Daniel Parrot who own and run the observatory, which is dedicated to finding new asteroids and comets.   The discovery is eligible for the Edgar Wilson Award.
    2021 U4 (Leonard)
    Gregory Leonard discovered a comet of 20th magnitude in images taken with the 1.5 m reflector of the Mt Lemmon Survey on 2021 October 31.30. It was placed on the PCCP as C6DP222. There were pre-discovery Mt Lemmon and PanSTARRS 1 & 2 observations from early in October. [CBET 5065, MPEC 2021-V22, 2021 November 2]. The comet is at perihelion at 1.8 au in 2021 December and is in a long period orbit. 
    2021 U5 (Catalina)
    A 19th magnitude object was discovered by the Catalina Sky Survey in images taken with the 0.68-m Schmidt on October 29.49. It was placed on the NEOCP as C2G7HL1, but moved to the PCCP when Nirmal Paul reported cometary activity. [MPEC 2021-V199, CBET 5070, 2021 November 10]. The comet is at perihelion at 2.4 au in 2022 January.
    2021 UL19 [A/Lemmon]
    The Mt Lemmon Survey discovered an object of 21st magnitude in images taken with the 1.5m reflector on October 17.33. It was placed on the PCCP as C68URH2. No evidence for cometary activity has been detected and the object has passed perihelion. [MPEC 2021-V236, 2021 November 10]. The object was at perihelion at 1.9 au in 2021 September. It is in a long-period retrograde orbit. JPL classify it as a Trans-Neptunian Object.
    2021 V1 (Rankin)
    David Rankin discovered a comet of 21st magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 November 5.16. It was placed on the PCCP as C6E8602. There were pre-discovery Mt Lemmon and PanSTARRS 1 & 2 images from October. [MPEC 2021-V167, CBET 5067, 2021 November 8/9]. The comet is at perihelion at 3.0 au in 2022 April and is in a very long period orbit.
    2021 V2 (P/Fuls)
    David Carson Fuls discovered a comet of 20th magnitude in images taken with the 1.5m reflector of the Mt Lemmon Survey on 2021 November 7.30. It was placed on the PCCP as C6FM222 and PanSTARRS made an independent discovery soon afterwards. There were pre-discovery PanSTARRS 1 images from August and PanSTARRS 2 images from October. [MPEC 2021-V169, CBET 5068, 2021 November 8/9]. The comet is at perihelion at 3.5 au in 2023 January and has a period of around 27 years.  The comet passed around 0.5 au from Jupiter in 1970 July.
    2021 V3 (P/PanSTARRS)
    PanSTARRS 1 discovered a 21st magnitude comet in images taken with the 1.8m Ritchey-Chretien on November 1.50. It was placed on the PCCP as P11o2nD and pre-discovery observations by PanSTARRS 1 & 2 in October were quickly found. The MPC then linked it to isolated tracklets from Mt Lemmon in 2012, Tenagra in 2012 and 2013 .  The comet was then linked to asteroid 2011 UE215, discovered by the Mt Lemmon survey on 2011 October 24.26. [MPEC 2021-V173, CBET 5069, 2021 November 9] The comet is at perihelion at 3.4 au in 2022 August and has a period of 9.7 years.  The comet passed 0.4 au from Jupiter in 2007 December, prior to which it was in a longer period orbit with perihelion at 4.0 au.
    2021 VQ8 [A/PanSTARRS]
    PanSTARRS 2 discovered an object in images taken with the 1.8m Ritchey-Chretien on November 6.4. It was briefly placed on the NEOCP as P21ofj3. The observations remain unpublished. The object was at perihelion at 2.0 au in 2021 October and has a period of around 30 years. JPL classify it as a Centaur. No cometary activity has been detected to date.
    2021 W1 (P/LINEAR)
    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 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 on 2077, when the comet passes within 0.3 au.
    2021 W2 (P/Kobayashi)
    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.
    2021 WT6 [A/Catalina]
    A 19th magnitude object was discovered by the Catalina Sky Survey in images taken with the 0.68-m Schmidt on November 29.47. It was placed on the NEOCP as C2NU8T1. [MPEC 2021-X73, 2021 December 3]. JPL class the object as a Centaur in a retrograde orbit with a period of about 13 years and it is at perihelion at 1.7 au in 2022 April. It may be worth looking for cometary activity as it approaches the Sun.
    2021 X1 (Maury-Attard)
    Alain Maury and Georges Attard discovered an object, of 19th magnitude, in images taken with the 0.28 m Schmidt of the MAP Observatory, San Pedro de Atacama, Chile (W94) on 2021 December 2.32. It was placed on the PCCP as 1C11G21. [MPEC 2021-X157, 2021 December 8]. The object is at perihelion at 3.2 au in 2023 May and has a retrograde parabolic orbit. At discovery it did not show any cometary characteristics, hence received an A/ designation. The MAP observatory is named for the initial letters of the last names of the amateur astronomers Alain Maury, Georges Attard and Daniel Parrot who own and run the observatory, which is dedicated to finding new asteroids and comets. Luca Buzzi and Andrea Aletti noted a coma in images taken on 2022 February23.83.  Eventually the MPC issued an MPEC, noting that Christavao Jacques had reported an elongated coma on December 30 [The MPEC has typos and says December 10, with discovery on December 12], but did not mention the February observation.  The CBET says that the MPC "inadvertently" gave it the A/ designation, despite many reports of cometary activity.  [MPEC 2022-J33, CBET 5119, 2022 May 5].  The discovery is eligible for the Edgar Wilson Award.
    A/2021 X2 (A/Kitt Peak)
    A 22nd magnitude object was discovered at Kitt Peak with the Bok 2.25m reflector on December 1.38. Subsequent astrometry and pre-discovery images from PanSTARRS 1 (October) and PanSTARRS 2 (November) show that it is in a parabolic orbit. It was placed on the PCCP as CO8YMM5. [MPEC 2021-X227, 2021 December 15]. To date it has shown no cometary activity. It is at perihelion at 3.0 au in 2022 July.
    2021 XZ3 [A/Lemmon]
    The Mt Lemmon Survey discovered an object of 21st magnitude in images taken with the 1.5m reflector on December 2.34. It was placed on the PCCP as C6UN4W2. No evidence for cometary activity has yet been detected. [MPEC 2021-X162, 2021 December 8]. The object is at perihelion at 3.1 au in 2022 October. It is in a retrograde orbit with a period of around 50 years. JPL classify it as a Centaur.
    2021 XS6 [A/Lemmon]
    The Mt Lemmon Survey discovered an object of 22nd magnitude in images taken with the 1.5m reflector on December 3.29. It was placed on the PCCP as C6V64K2. There were pre-discovery PanSTARRS 1 and 2 observations from 2021 October and November. No evidence for cometary activity has yet been detected. [MPEC 2021-Y46, 2021 December 20]. The object is at perihelion at 3.9 au in 2022 February. It is in a near perpendicular orbit with a period of nearly 250 years. JPL classify it as a Trans-Neptunian Object.
    2021 Y1 (ATLAS)
    A 19th magnitude object was discovered in images taken with the 0.5m Schmidt at Mauna Loa on December 26.29 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) team. It was posted on the PCCP as A10DXMA. Follow-up observations by astrometrists showed cometary activity. Pre-discovery images taken by M Holbroook at Pleasant Groves Observatory on two days in November were then linked to the comet. [MPEC 2022-A50, CBET 5088 (dated as issued in 2021) and 5089 (corrected to 2022), 2022 January 6]. The comet is at perihelion at 2.0 au in 2023 April.  It may reach 12th magnitude for several months around the time of perihelion, though could be brighter.
    2021 YP [A/Lemmon]
    The Mt Lemmon Survey discovered an object of 21st magnitude in images taken with the 1.5m reflector on December 21.29. It was placed on the PCCP as C6XDJV2. There were pre-discovery PanSTARRS 1 and 2 observations from 2021 November. No evidence for cometary activity has yet been detected. [MPEC 2021-Y74, 2021 December 30]. The object is at perihelion at 1.9 au in 2022 April. It is in a retrograde orbit with a period of 15 years. JPL classify it as a Centaur.
    Ephemerides of current comets are available on the CBAT ephemeris page and positions of newly discovered comets are on the Possible Comet Confirmation Page.
    More information on LINEAR. A list of comets discovered by selected search programs.
    The Northumberland refractor is the telescope that was used in the search for Neptune. It now has a 0.30-m f20 doublet lens which gives a stellar limiting magnitude of around 15 at the zenith on good nights. The Thorrowgood refractor was built in 1864 and has a 0.20-m f14 doublet lens; it is currently out of action as the dome has stuck.
    Published by Jonathan Shanklin. Jon Shanklin - jds@ast.cam.ac.uk