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ALPO Comet News for September 2021

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#1 Carl H.

Carl H.

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Posted 06 September 2021 - 06:47 PM

ALPO COMET NEWS FOR SEPTEMBER 2021
A Publication of the Comets Section of the Association of Lunar and Planetary Observers
By Carl Hergenrother

 

The monthly Association of Lunar and Planetary Observers (ALPO) Comet News PDF can be found on the ALPO Comets Section website @ http://www.alpo-astr....org/cometblog/. A shorter version of this report is posted here (minus the magnitude estimates, lightcurves, images, and other figures contained in the full PDF). The ALPO Comet Section welcomes all comet related observations, whether textual descriptions, images, drawings, magnitude estimates, or spectra. You do not have to be a member of ALPO to submit material, though membership is encouraged. To learn more about the ALPO, please visit us @ http://www.alpo-astronomy.org. We can also be reached at < comets @ alpo-astronomy.org >.

 

Summary

 

While we are still waiting for the next “Big One” or even the next “Bright Enough to be seen in my binoculars” comet, September sees quite a few comets bubbling around magnitude 10 to 11. 8P/Tuttle may get as bright as magnitude 8.5 though it is solely a southern hemisphere object. As many as 5 comets, 4P/Faye, 6P/d’Arrest, 67P/Churyumov-Gerasimenko, C/2019 L3 (PANSTARRS), and C/2020 T2 (PANSTARRS), could brighten into the magnitude 10 to 11 range.

 

C/2021 A1 (Leonard) still has the potential to be an interesting object this December. Recent observations suggest it may be brightening at a fast rate, so imagers and large aperture visual observers are encouraged to observe it this month as it may brighten to 12-13th magnitude by the end of the month.

 

Comets Section News

During August, the ALPO Comets Section received 48 images and/or sketches from Dan Bartlett, Michel Deconinck, Christian Harder, Gianluca Masi, Martin Mobberley, Mike Olason, and Uwe Pilz and 91 visual and CCD magnitude measurements from Michel Deconinck, J. J. Gonzalez, Mike Olason, and Chris Wyatt of the following comets: C/2021 O1 (Nishimura), P/2021 N2 (Fuls), P/2021 N1 (ZTF), P/2021 L2 (Leonard), C/2020 T2 (Palomar), C/2020 S3 (Erasmus), C/2020 PV6 (PANSTARRS), C/2020 K6 (Rankin), C/2020 K1 (PANSTARRS), C/2020 J1 (SONEAR), C/2020 F5 (MASTER), C/2019 U5 (PANSTARRS), C/2019 L3 (ATLAS), C/2019 K7 (Smith), C/2019 F1 (ATLAS-Africano), C/2018 U1 (Lemmon), C/2017 U7 (PANSTARRS), C/2017 K2 (PANSTARRS), 424P/La Sagra, 402P/LINEAR, 395P/Catalina-NEAT, 378P/McNaught, 284P/McNaught, 252P/LINEAR, 246P/NEAT, 241P/LINEAR, 193P/LINEAR-NEAT, 132P/Helin-Roman-Alu, 119P/Parker-Hartley, 110P/Hartley, 108P/Ciffreo, 67P/Churyumov-Gerasimenko, 29P/Schwassmann-Wachmann, 19P/Borrelly, 17P/Holmes, 15P/Finlay, 10P/Tempel, 7P/Pons-Winnecke, 6P/d’Arrest, and 4P/Faye.

 

We’d like to especially thank Dan Bartlett who has graciously agreed to contribute his observations to the ALPO Comets Section.

 

In addition to observations submitted directly to the ALPO, we occasionally use data from other sources to augment our analysis. We would like to acknowledge with thanks observations submitted directly to the ALPO as well as those originally submitted to the International Comet Quarterly, Minor Planet Center, and COBS Comet Observation Database. We would also like to thank the Jet Propulsion Laboratory for making available their Small-Body Browser and Orbit Visualizer and Seiichi Yoshida for his Comets for Windows programs that is used to produce the lightcurves in these pages. And last but not least, we’d like to thank Syuichi Nakano and the Minor Planet Center for their comet orbital elements, the asteroid surveys for their discoveries, and all of the observers who volunteer their time to adding to our knowledge of these amazing objects.

 

Comets Calendar for September 2021

 

Sep 04-05  – 15P/Finlay passes within 0.5 deg of open cluster NGC 2331
Sep 06  – New Moon
Sep 08  – 283P/Spacewatch at perihelion (q = 2.13 au, 8.4-year orbit, V~20-21, poor apparition, too close to Sun to be observed)
Sep 08  – C/2021 K2 (MASTER) at perihelion (q = 5.47 au, long-period comet, V ~ 17-18)
Sep 08  – 4P/Faye at perihelion (q = 1.62 au, 7.5-year orbit, V ~ 10, discovered in 1843, 22nd observed return, more below)
Sep 10  – 108P/Ciffreo at perihelion (q = 1.66 au, 7.2-year orbit, V ~ 15, discovered on 1985 November 8 on images taken on 1P/Halley with a 0.9-m Schmidt at Caussols, France; 6th observed return, reached 10th mag and was observed to split in 1985)
Sep 12  – 284P/McNaught at perihelion (q = 2.30 au, 7.1-year orbit, V ~ 16, discovered in 2007, 3rd observed return, reached 13th mag at 2007 and 2013 returns)
Sep 13  – First Quarter Moon
Sep 15  – C/2020 K6 (Rankin) at perihelion (q = 5.87 au, long-period comet, V ~ 19)
Sep 17  – 6P/d’Arrest at perihelion (q = 1.35 au, 6.5-year orbit, V ~ 10-11, discovered in 1678 and 1851, 21st observed return, reached 5th magnitude in 1976)
Sep 18-19  – 6P/d’Arrest passes in front of the Trifid Nebula (M20)
Sep 20  – Full Moon
Sep 20  – 423P/Lemmon at perihelion (q = 5.42 au, 15.3-year orbit, V ~ 22-23, discovered in 2008, 2nd observed return, was brighter at V ~ 18-19 in 2009 when it was possibly in outburst)
Sep 20  – 425P/Kowalski at perihelion (q = 2.89 au, 15.9-year orbit, V ~ 19-20, discovered in 2005, 2nd observed return)
Sep 20-21  – 6P/d’Arrest travels in front of the nebulosity connected to and NE of the Lagoon Nebula (M8)
Sep 22  – C/2021 J2 (PANSTARRS) at perihelion (q = 4.71 au, 1253-year orbit, V ~ 20-21)
Sep 22  – P/2004 R3 (LINEAR-NEAT) at perihelion (q = 3.55 au, 7.5-year orbit, not seen since 2004 when it peaked at V ~17-18)
Sep 22  – 67P/Churyumov-Gerasimenko passes within 0.5 deg of Hind’s Variable Nebula (NGC 1555)
Sep 25  – C/2020 PV6 (PANSTARRS) at perihelion (q = 2.30 au, 271-year orbit, V ~ 13-14)
Sep 25  – 8P/Tuttle near 12th mag galaxy NGC 3200
Sep 26-27 – 8P/Tuttle passes within 0.5 deg of planetary nebula Ghost of Jupiter (NGC 3242)
Sep 28  – Last Quarter Moon

 

Comets Brighter Than Magnitude 10

 

8P/Tuttle

 

Discovered on 1790 January 9 by Pierre F. A. Mechain

Rediscovered on 1858 January 5 by Horace Tuttle

 

Orbit (from Minor Planet Center, MPEC 2021-P47)

 

   8P/Tuttle                                                                   
Epoch 2021 July 5.0 TT = JDT 2459400.5                                         
T 2021 Aug. 27.73755 TT                                 Rudenko                
q   1.0260106            (2000.0)            P               Q                 
n   0.07228615     Peri.  207.48893     -0.26849376     -0.50829747            
a   5.7073258      Node   270.20410     +0.96326296     -0.13641415            
e   0.8202292      Incl.   54.91122     +0.00596490     -0.85030868            
P  13.6                                                                        
From 210 observations 2008 Feb. 12-2021 Aug. 4, mean residual 0".5.            
     Nongravitational parameters A1 = +0.44, A2 = +0.2030.    

                 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

8P/Tuttle                                                        Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  08 55  +02 13   1.028   1.823    26M   Hya   8.9     0    6
2021-Sep-06  09 11  -01 50   1.036   1.813    27M   Hya   8.7     0    8
2021-Sep-11  09 28  -05 56   1.049   1.808    29M   Hya   8.6     0   10
2021-Sep-16  09 44  -10 00   1.068   1.810    30M   Hya   8.5     0   11
2021-Sep-21  10 01  -14 01   1.091   1.817    31M   Hya   8.5     0   13
2021-Sep-26  10 18  -17 55   1.119   1.832    32M   Hya   8.6     0   14
2021-Oct-01  10 36  -21 40   1.150   1.852    33M   Hya   8.6     0   15
2021-Oct-06  10 53  -25 14   1.186   1.878    33M   Hya   8.8     0   16

 

Comet Magnitude Formula

 

m1 = 7.0 + 5 log d + 20 log r(t-25) [Ref: Seiichi Yoshida]

 

8P/Tuttle was discovered during two widely separated apparitions. Pierre François André Méchain made the first discovery on 1790 January 9. Sixty-eight years and 5 orbits later, 8P was re-discovered by Horace Parnell Tuttle on 1858 January 5. With a 13.6-year period, 8P/Tuttle is making its 13th observed return and 18th return going back to the initial 1790 discovery apparition. Tuttle’s relatively large semi-major axis of 5.7 au and inclination of 54.9° makes it a Halley-type rather than a Jupiter-family comet. Its orbit currently passes 0.096 au from Earth and a relatively safe 0.74 au from Jupiter.

 

The comet’s best apparitions occurred in 1980/1981 when it reached 6th magnitude and at its previous return in 2007/2008 when it passed 0.25 au from Earth and reached 5th magnitude. Looking ahead, Tuttle should have an even better return in 2048/2049 when it comes within 0.18 au of Earth and brightens to 4th magnitude.

 

Meteor watchers may remember that 8P/Tuttle is the parent body of the Ursid meteor shower in December. 8P’s highly inclined orbit not only results in the Ursids radiating from the far northern constellation of Ursa Minor, but also in apparitions that are best observed from the northern hemisphere before perihelion and from the southern hemisphere after perihelion. Poor placement close to the Sun over the past few months means observing this year’s return will be limited to the southern hemisphere.

 

Being one of the more intrinsically bright short-period comets, Tuttle can get bright enough to be seen in small telescopes even during poor apparitions. Even with a large minimum distance to Earth on September 12 of 1.81 au, Tuttle is expected to brighten to magnitude 8.5 in September. Southern observers will be able to follow Tuttle as it moves through Hydra low in the morning sky.

 

C/2020 T2 (Palomar)

 

Discovered 2020 October 7 at 19th magnitude by the Zwicky Transient Facility (ZTF) with the 1.2-m Samuel Oschin Schmidt on Mount Palomar
Dynamically old long-period comet with orbital period of 5560 years

 

Orbit (from Syuichi Nakano, Nakano Note NK 4449)

 

   C/2020 T2 (Palomar)
Epoch 2021 July 5.0 TT = JDT 2459400.5 
T 2021 July 11.14758 TT                                 Nakano
q   2.0546863            (2000.0)            P               Q
z  +0.0032038      Peri.  150.38316     -0.53887199     +0.70302914
+/-0.0000009      Node    83.04827     -0.83514131     -0.37375209
e   0.9934172      Incl.   27.87301     -0.11025416     -0.60502843
From 682 observations 2019 Dec. 11-2021 Apr. 2, mean residual 0".37.
  (1/a)org.= +0.002916, (1/a)fut.= +0.003827 (+/-0.000001), Q= 8.
  The comet will pass 3.10 AU from Jupiter on 2022 June 7 UT.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

C/2020 T2 (Palomar)                                              Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  15 17  -15 30   2.146   2.217    72E   Lib  10.5    17   50
2021-Sep-06  15 27  -17 07   2.163   2.282    70E   Lib  10.7    15   49
2021-Sep-11  15 36  -18 40   2.183   2.348    68E   Lib  10.8    14   47
2021-Sep-16  15 46  -20 07   2.203   2.415    65E   Lib  10.9    13   45
2021-Sep-21  15 56  -21 29   2.225   2.483    63E   Sco  11.0    11   43
2021-Sep-26  16 06  -22 47   2.248   2.552    61E   Sco  11.2    10   41
2021-Oct-01  16 17  -23 59   2.272   2.622    58E   Sco  11.3     9   39
2021-Oct-06  16 27  -25 07   2.298   2.692    56E   Sco  11.5     8   36

 

Comet Magnitude Formula (from fit to ALPO and COBS data)

 

m1 = 1.8 + 5 log d +21.9 log r(t-20)

 

C/2020 T2 (PANSTARRS) has been hanging around 10-11th magnitude for the past few months. Visual observers estimated PANSTARRS between magnitude 9.7 and 10.9 in August with a moderately condensed coma ranging from 3’ to 7’ across.

 

C/2020 T2 has started to slowly fade. As a result, September should see it decrease in brightness from around magnitude 10.5 to 11.3. As the comet moves through the evening constellations of Libra (Sep 1-16) and Scorpius (16-30), it will be a well-placed for southern hemisphere observers, but a rather low object for northern observers.

 

Looking ahead, C/2020 T2 will pass in front of the photogenic nebulosity of the Antares/Rho Ophiuchi area during the first week of October.

 

4P/Faye

 

Discovered visually on 1843 November 23 by the Herve Faye

 

Orbit (from Syuichi Nakano, Nakano Note NK 4500)

 

  4P/Faye
Epoch 2021 Sept. 23.0 TT = JDT 2459480.5 
T 2021 Sept. 8.83079 TT                                 Nakano
q   1.6188553            (2000.0)            P               Q
n   0.13183220     Peri.  206.99673     +0.76783984     -0.63988277
a   3.8234467      Node   192.93148     +0.61006246     +0.74517843
e   0.5765979      Incl.    8.00830     +0.19556526     +0.18777418
P   7.48
From 4264 observations 2006 Aug.-2021, mean residual 0".76.
  Nongravitational parameters A1 = +0.64 +/- 0.01, A2 = -0.0389 +/- 0.0003.
  2021 July-August observations show the residuals of +20" mainly for
  Right Ascension from the prediction in NK 3622 (= HICQ 2020/2021)
  with the delta-T correction = -0.01 day.
  The comet has passed 0.63 AU from Jupiter on 2018 Mar. 7 UT.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

4P/Faye                                                           Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  04 48  +18 49   1.621   1.352    85M   Tau  10.8    54   29
2021-Sep-06  05 01  +18 36   1.619   1.318    87M   Tau  10.7    56   29
2021-Sep-11  05 14  +18 17   1.619   1.285    89M   Tau  10.7    58   29
2021-Sep-16  05 26  +17 54   1.620   1.254    90M   Tau  10.6    60   29
2021-Sep-21  05 38  +17 25   1.623   1.224    93M   Tau  10.6    61   30
2021-Sep-26  05 49  +16 52   1.628   1.194    95M   Ori  10.6    62   30
2021-Oct-01  06 00  +16 14   1.634   1.166    97M   Ori  10.6    63   31
2021-Oct-06  06 10  +15 34   1.642   1.139   100M   Ori  10.6    64   32

 

Comet Magnitude Formula (from fit to ALPO and COBS data)

 

m1 = 10.3 + 5 log d + 10 log r

 

4P/Faye was visually discovered by Herve Faye (Royal Observatory, Paris, France) on 1843 November 23 at 5th-6th magnitude. Only days after discovery, the comet was reported to be visible to the naked eye. For unknown reasons, Faye was abnormally bright in 1843. Since then, it has peaked at 9th magnitude as it did during its best returns in 1991 and 2006.

 

This year’s apparition is the 22nd observed return with the comet only having been missed at perihelia in 1903 and 1918. 2021 is a moderately good but not great return and should see Faye reach magnitude 10.6 at the end of September. Even after perihelion, the comet will slowly approach Earth, not reaching a minimum geocentric distance till December 5 at 0.94 au. The decreasing Earth-comet distance will keep Faye in the 10-11th magnitude range for the next few months.

 

Faye is currently a morning object observable from both hemispheres as its moves through Taurus (Sep 1-26) and Orion (26-30). Looking ahead to next month, 4P will travel in front of the Rosette Nebula on October 3-5. It should be quite the sight considering the nice coma structure and tail it is currently displaying in deep images.

 

6P/d’Arrest

 

Discovered on 1851 June 28 by the Heinrich Ludwig d'Arrest

 

Orbit (from Syuichi Nakano, Nakano Note NK 4445)

 

  6P/d'Arrest
Epoch 2021 Sept. 23.0 TT = JDT 2459480.5 
T 2021 Sept. 17.78204 TT                                Nakano
q   1.3546116            (2000.0)            P               Q
n   0.15061475     Peri.  178.10208     +0.73305041     +0.64381249
a   3.4985739      Node   138.93551     -0.62836543     +0.76449697
e   0.6128103      Incl.   19.51238     -0.26037278     -0.03240149
P   6.54
From 1865 observations 2008-2021, mean residual 0".66.
  Nongravitational parameters A1 = +0.35 +/- 0.01, A2 = +0.1180 +/- 0.0005.
  Residuals on 2021 Apr.-May observations were -40" for Right Ascensin and
  +12" for Declination from the prediction in NK 3623 (= HICQ 2021) with
  the delta-T correction = +0.018 day.
  The comet has made the 21st appearances after AD 1678 (IAUC 5283).
  Comet will pass 0.97 AU from Jupiter on 2039 Apr. 1 UT.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

6P/d'Arrest                                                       Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  17 09  -14 05   1.369   0.779    99E   Oph  11.5    32   63
2021-Sep-06  17 22  -16 43   1.362   0.791    97E   Oph  11.3    29   65
2021-Sep-11  17 36  -19 14   1.357   0.806    96E   Oph  11.1    27   66
2021-Sep-16  17 52  -21 36   1.355   0.824    95E   Sgr  10.9    25   67
2021-Sep-21  18 08  -23 46   1.355   0.844    93E   Sgr  10.7    24   68
2021-Sep-26  18 25  -25 43   1.358   0.866    92E   Sgr  10.5    22   68
2021-Oct-01  18 43  -27 25   1.363   0.892    91E   Sgr  10.4    21   68
2021-Oct-06  19 02  -28 51   1.371   0.920    91E   Sgr  10.3    20   68

 

Comet Magnitude Formula (from fit to ALPO and COBS data)

 

m1 = 5.4 + 5 log d + 32.1 log r(t-60)

 

Heinrich Louis d’Arrest discovered 6P visually in June 1851 though we now know that it had been previously observed by Phillipe la Hire in 1678. Long-time comet watchers may remember this comet’s excellent apparition in 1976 when it passed 0.15 au from Earth and reached 5th magnitude. d’Arrest’s perihelion distance is larger now (1.35 au) so such close approaches are no longer possible. This year, closest approach to Earth was on August 2 at 0.75 au and perihelion will be on September 17.

 

Last month we mentioned that CCD photometry by Michael Lehmann found the comet a magnitude or so brighter than predicted. Visual observations by Chris Wyatt and J. J. Gonzalez confirm that d’Arrest is brighter than expected. If the comet continues its current brightness trend, it may approach a peak brightness around magnitude 10.0 in late October/early November. According to the brighter prediction, d’Arrest should brighten in September from magnitude 11.5 to 10.4 as it moves through the evening constellations of Ophiuchus (Sep 1-3), Serpens (3), Ophiuchus (3-13), and Sagittarius (13-30). Photo Op Alert: 6P will travel through the Trifid Nebula (M20) and very close to the Lagoon Nebula (M8) between September 18 and 21.

 

7P/Pons-Winnecke

 

Discovered on 1819 June 12 by the Jean-Luis Pons
Rediscovered on 1858 March 9 by Friedrich August Theodor Winnecke

 

Orbit (from Minor Planet Center, MPEC 2021-P47)

 

   7P/Pons-Winnecke                                                            
Epoch 2021 July 5.0 TT = JDT 2459400.5                                         
T 2021 May 27.11293 TT                                  Rudenko                
q   1.2342367            (2000.0)            P               Q                 
n   0.15623635     Peri.  172.59644     -0.06057374     +0.92307530            
a   3.4141400      Node    93.37530     -0.93419396     +0.08160384            
e   0.6384926      Incl.   22.36338     -0.35158564     -0.37586274            
P   6.31                                                                       
From 1774 observations 1921 Apr. 28-2021 July 29, mean residual 0".7.          
     Nongravitational parameters A1 = +0.02, A2 = +0.0021.                     

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

7P/Pons-Winnecke                                                 Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  23 45  -52 00   1.680   0.812   134M   Phe  12.5     0   78
2021-Sep-06  23 39  -51 47   1.717   0.857   133M   Phe  12.8     0   78
2021-Sep-11  23 34  -51 18   1.755   0.904   133M   Phe  13.1     0   79
2021-Sep-16  23 28  -50 36   1.792   0.955   132E   Phe  13.4     0   80
2021-Sep-21  23 24  -49 43   1.830   1.009   130E   Gru  13.7     0   80
2021-Sep-26  23 20  -48 40   1.868   1.067   129E   Gru  14.0     2   82
2021-Oct-01  23 18  -47 29   1.907   1.127   127E   Gru  14.3     3   83
2021-Oct-06  23 16  -46 12   1.945   1.191   125E   Gru  14.5     4   84

 

Comet Magnitude Formula (from ALPO and COBS data)

 

m1 = 9.7 + 5 log d + 26.6 log r(t-11)

 

Comet 7P/Pons-Winnecke was an 8th magnitude object when visually discovered by Jean-Luis Pons on 1819 June 12. Even though a short-period orbit was calculated at that time, it unfortunately was not precise enough to support the comet’s recovery at later returns. Thirty-nine years later on 1858 March 9, Friedrich August Theodor Winnecke re-discovered Pons-Winnecke. Throughout the 19th and early 20th century, Pons-Winnecke routinely reached 6th magnitude during its better apparitions. In 1927 during an especially close approach to Earth (0.04 au), the comet peaked at magnitude 3.5. Unfortunately, it hasn’t had a bright return since 1939 (6th  magnitude) and nowadays usually gets no brighter than ~10-11th magnitude. The recent drought of bright apparitions is due to an increase in perihelion distance from 0.76 au in 1841 to a maximum of 1.26 au in 1989. This year’s perihelion occurred on 2021 May 27 at 1.23 au as 7P is still close to its maximum perihelion distance.

 

The perihelion distance of Pons-Winnecke will steadily decrease over the coming decades from this year’s 1.23 au to 1.13 au in 2027, 0.98 au in 2039, 0.87 au in 2051, and a minimum near 0.84 au for many perihelia from 2062 through the end of the 21st century. The smaller distances will once again allow close approaches to Earth, in particular, in 2045 (0.21 au), 2062 (0.17 au), 2073 (0.19 au), and 2084 (0.31 au).

 

Pons-Winnecke was at perihelion back in May, but it still a reasonably bright object due to a strong seasonal effect resulting in a peak brightness in the weeks after perihelion. Chris Wyatt observed the comet fading from around magnitude 11.6 on August 6 to 12.4 on August 31. He found the comet to be slightly condensed with a 4’ coma.

 

Pons-Winnecke should fade from around magnitude 12.5 to 14.3 as it moves through the southern constellations of Phoenix (Sep 1-18) and Grus (18-30). Its location at southern declinations makes it a difficult object from the northern hemisphere but well placed for southern hemisphere observers.

 

15P/Finlay

 

Discovered 1886 September 26 by the William Henry Finlay
Short-period comet with orbital period of ~6.56 years

 

Orbit (from Syuichi Nakano, Nakano Note NK 4446)

 

15P/Finlay
Epoch 2021 July 5.0 TT = JDT 2459400.5 
T 2021 July 13.47387 TT                                 Nakano
q   0.9919899            (2000.0)            P               Q
n   0.15015570     Peri.  347.82382     +0.99928830     -0.02520905
a   3.5057007      Node    13.71407     +0.03587528     +0.86500484
e   0.7170352      Incl.    6.79753     -0.01165603     +0.50112986
P   6.56
From 1134 observations 2008-2021, mean residual 0".72.
  Nongravitational parameters A1 = +0.24 +/- 0.01, A2 = -0.0232 +/- 0.0001.
  Residuals on 2021 April were +135" for Right Ascension and +170" for
  Declination from the prediction in NK 3627 (= HICQ 2020/2021) with
  the delta-T correction = -0.07 day.
  The comet has passed 0.28 AU from Jupiter on 2004 May 8 UT.
  The comet has made the 16th appearances after AD 1886.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

15P/Finlay                                                        Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  06 52  +26 56   1.216   1.424    56M   Cnc  12.4    36    9
2021-Sep-06  07 07  +26 58   1.256   1.443    58M   Cnc  12.7    38    8
2021-Sep-11  07 21  +26 56   1.298   1.459    60M   Cnc  12.9    40    8
2021-Sep-16  07 34  +26 50   1.341   1.473    62M   Cnc  13.2    42    8
2021-Sep-21  07 46  +26 43   1.386   1.484    64M   Cnc  13.4    45    8
2021-Sep-26  07 58  +26 33   1.431   1.492    66M   Cnc  13.7    47    8
2021-Oct-01  08 08  +26 23   1.477   1.497    69M   Cnc  13.9    50    8
2021-Oct-06  08 18  +26 14   1.523   1.499    71M   Cnc  14.1    53    8

 

Comet Magnitude Formula (from ALPO and COBS data)

 

m1 = 13.2 + 5 log d + 10 log r

 

15P/Finlay was discovered in 1886 by William Henry Finlay at the Royal Observatory at Cape of Good Hope in South Africa. The current apparition marks the 16th observed return of 15P though it was missed at a number of returns (1900, 1913, 1933, 1940, and 1947). Its best return was in 1906 when it passed 0.27 au from Earth and reached 6th magnitude. During its previous return in 2014/2015, 15P experienced two outbursts of 2-3 mag outburst with the brightest reaching 7th magnitude.

 

Uwe Pilz and Chris Wyatt observed 15P between magnitude 11.4 and 11.9 in early August with a 1.6 to 2’ coma. J. J. Gonzalez found the comet to be as bright as magnitude 10.1 on August 6th with a 5’ coma.

 

Perihelion was two months ago on July 13th at 0.99 au. Finlay should become a difficult visual object as it fades from magnitude 12.4 to 13.9 as it moves away from the Earth and Sun. The comet is a morning object in Gemini (Sep 1-27) and Cancer (27-30) and better placed for northern observers.

 

67P/Churyumov-Gerasimenko

 

Discovered 1969 September 11 by the Klim Ivanovic Churyumov and Svetlana Ivanovna Gerasimenko
Short-period comet with orbital period of ~6.43 years

 

Orbit (from Minor Planet Center, MPEC 2021-P47)

 

  67P/Churyumov-Gerasimenko                                                    
Epoch 2021 Nov. 2.0 TT = JDT 2459520.5                                         
T 2021 Nov. 2.06355 TT                                  Rudenko                
q   1.2106211            (2000.0)            P               Q                 
n   0.15340714     Peri.   22.13460     +0.52349722     -0.85108778            
a   3.4559889      Node    36.33252     +0.77125182     +0.45339138            
e   0.6497034      Incl.    3.87150     +0.36210674     +0.26473730            
P   6.42                                                                       
From 7006 observations 1995 July 3-2021 Aug. 5, mean residual 0".7.            
     Nongravitational parameters A1 = +0.07, A2 = +0.0106.                     

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

67P/Churyumov-Gerasimenko                                         Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  03 03  +13 10   1.430   0.711   111M   Ari  12.0    63   37
2021-Sep-06  03 20  +14 34   1.399   0.666   111M   Ari  11.8    64   35
2021-Sep-11  03 38  +16 00   1.370   0.625   112M   Tau  11.5    66   34
2021-Sep-16  03 57  +17 25   1.343   0.588   112M   Tau  11.2    68   32
2021-Sep-21  04 17  +18 49   1.318   0.555   112M   Tau  10.9    69   31
2021-Sep-26  04 38  +20 11   1.295   0.526   112M   Tau  10.7    70   30
2021-Oct-01  04 59  +21 27   1.274   0.500   111M   Tau  10.4    72   28
2021-Oct-06  05 22  +22 38   1.256   0.479   111M   Tau  10.2    73   27

 

Comet Magnitude Formula (from Seiichi Yoshida)

 

m1 = 9.5 + 5 log d + 14.0 log r(t-40)

 

67P was discovered on photographic plates taken on 1969 September 11 by Kiev University Astronomical Observatory astronomers Klim Ivanovic Churyumov and Svetlana Ivanovna Gerasimenko working with a 50-cm Maksutov astrograph at the Alma-Ata Astrophysical Institute in current day Kazakhstan. The current apparition is 67P’s 9th observed return with perihelion occurring on 2021 November 2 at 1.21 au. A close approach to Earth at 0.42 au on November 12 makes this the comet’s best return since 1982 when it came marginally closer to Earth at 0.39 au. At that return, a peak brightness of 9th magnitude was reached so a similar brightness should occur this November and December when it will be a morning object visible from both hemispheres. 67P was famously the target of the ESA Rosetta/Philae mission, the only spacecraft to have orbited and landed on a comet. This will be 67P’s first return since Rosetta ended its mission by soft landing onto the comet’s surface.

 

Chris Wyatt, J. J. Gonzalez, Mike Olason, and Michel Deconinck observed 67P in August between magnitude 12.7 and 13.9 with a small 0.8 to 1.5’ coma. Chris was also able visually observe a tail up to 2.3’ in length with his 0.4-m reflector. The tail is also a striking feature in CCD images such as Mike Olason’s image from August 2 and Dan Bartlett’s image from August 11 (see PDF version of this report).

 

September should see 67P brighten from 12th to 10th magnitude as its moves through Aries (Sep 1-7) and Taurus (7-30) in the morning sky. Photo Op Alert: On September 22, 67P passes within 0.5 deg of Hind’s Variable Nebula (NGC 1555).

 

C/2017 K2 (PANSTARRS)

 

Discovered 2017 May 21 by the Pan-STARRS survey with the Pan-STARRS1 1.8-m on Haleakala
Dynamically old long-period comet

 

Orbit (from Syuichi Nakano, Nakano Note NK 4448)

 

   C/2017 K2 (PANSTARRS)
Epoch 2022 Dec. 7.0 TT = JDT 2459920.5 
T 2022 Dec. 19.67178 TT                                 Nakano
q   1.7969443            (2000.0)            P               Q
z  -0.0004734      Peri.  236.19715     +0.01818315     +0.04923207
+/-0.0000004      Node    88.23537     -0.18094861     +0.98245608
e   1.0008506      Incl.   87.56309     -0.98332445     -0.17987844
From 4213 observations 2013 May 12-2021 May 3, mean residual 0".44.
  (1/a)org.= +0.000028, (1/a)fut.= +0.001121 (+/-0.000000), Q= 9.
  The comet will pass 2.66 AU from Jupiter on 2024 Oct. 15 and
  7.88 AU from Uranus on 2029 Oct. 16 UT.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

C/2017 K2 (PANSTARRS)                                             Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  16 57  +32 37   5.461   5.385    88E   Her  12.5    67   17
2021-Sep-06  16 56  +31 35   5.418   5.391    86E   Her  12.5    65   17
2021-Sep-11  16 56  +30 32   5.376   5.398    83E   Her  12.4    62   16
2021-Sep-16  16 56  +29 30   5.333   5.406    80E   Her  12.4    60   15
2021-Sep-21  16 57  +28 27   5.290   5.414    77E   Her  12.4    57   14
2021-Sep-26  16 58  +27 26   5.247   5.422    74E   Her  12.3    55   12
2021-Oct-01  16 59  +26 25   5.204   5.430    71E   Her  12.3    53   10
2021-Oct-06  17 01  +25 26   5.160   5.437    68E   Her  12.3    50    7

 

Comet Magnitude Formula (from ALPO and COBS data)

 

m1 =  2.2 + 5 log d + 9.0 log r

 

C/2017 K2 (PANSTARRS) was discovered on 2017 May 21 by the Pan-STARRS1 1.8-m telescope at Haleakala on the Hawaiian island of Maui. At discovery the comet was around 21st magnitude and located at 16.1 au from the Sun. Pre-discovery observations were found back to May of 2013 when the comet was 23.7 au from the Sun. For comparison Uranus has a semi-major axis of 19.2 au.

 

C/2017 K2 (PANSTARRS) is still many months from a 2022 December 19 perihelion at 1.80 au when it should reach 6-7th magnitude. Several visual observations were made in August by Michel Deconinck, J. J. Gonzalez and Chris Wyatt as well as a CCD measurement by Mike Olason. Magnitude measurements ranged between 12.2 and 13.3 with most of the estimates falling between 13.0 and 13.3. All observers found a small moderately condensed coma of ~1-2’.

 

C/2017 K2 is an evening object in Hercules and is better placed for northern observers though it also visible from the southern hemisphere. The comet will continue to slowly brighten throughout the remainder of 2021 and all of 2022.

 

C/2019 L3 (ATLAS)

 

Discovered 2019 June 10 by the ATLAS survey with one of their 0.5-m f/2 Schmidt
Dynamically old long-period comet

 

Orbit (from Syuichi Nakano, Nakano Note NK 4342)

 

   C/2019 L3 (ATLAS)
Epoch 2022 Jan. 21.0 TT = JDT 2459600.5 
T 2022 Jan. 9.61848 TT                                  Nakano
q   3.5544913            (2000.0)            P               Q
z  -0.0004539      Peri.  171.61068     -0.26052581     -0.66630775
+/-0.0000010      Node   290.79047     +0.83675882     +0.20517556
e   1.0016135      Incl.   48.36122     +0.48162328     -0.71689398
From 1281 observations 2019 June 10-2021 Jan. 4, mean residual 0".36.
  (1/a)org.= +0.000021, (1/a)fut.= -0.000735 (+/-0.000001), Q= 8.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

C/2019 L3 (ATLAS)                                                 Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  06 56  +45 31   3.748   4.140    60M   Aur  11.0    43    0
2021-Sep-06  07 03  +45 07   3.733   4.070    63M   Lyn  10.9    46    0
2021-Sep-11  07 09  +44 44   3.720   3.997    66M   Lyn  10.9    49    0
2021-Sep-16  07 15  +44 20   3.707   3.923    70M   Lyn  10.8    52    0
2021-Sep-21  07 20  +43 56   3.694   3.847    73M   Aur  10.8    56    0
2021-Sep-26  07 25  +43 32   3.682   3.770    77M   Aur  10.7    59    0
2021-Oct-01  07 30  +43 07   3.671   3.692    80M   Aur  10.7    63    0
2021-Oct-06  07 34  +42 42   3.660   3.613    84M   Lyn  10.6    67    0

       
Comet Magnitude Formula (from ALPO and COBS data)

 

m1 = 3.3 + 5 log r + 8.0 log r

 

C/2019 L3 (ATLAS) is a far northern object in the morning sky. The comet’s location in Auriga (Sep 1), Lynx (Sep 1-16), and back to Auriga (Sep 16-30) makes it well place for northern hemisphere observers but invisible from the southern hemisphere. Three measurements were submitted to the ALPO from J. J. Gonzalez, Mike Olason, and Uwe Pilz. All three observers found the comet around magnitude 11.2 to 11.4 with coma between 0.7 and 2.0’ in diameter.

 

C/2019 L3 is still a few months from a 2022 January 9 perihelion at 3.57 au. The large perihelion distance means C/2019 L3 should remain a visual object well into 2022 and possibly even 2023. The comet has been brightening at rapid rate since discovery. If we assume a conservative 2.5n = 8 rate of brightening from now till perihelion, it could become slightly brighter than magnitude 10 between December and February. At that time, it will be well placed in the opposition sky though perhaps a little low for southern hemisphere observers.

 

Fainter Comets of Interest (Fainter than 13.0)

 

29P/Schwassmann-Wachmann

 

Discovered 1927 November 15 by the Arnold Schwassmann and Arno Arthur Wachmann at the Hamburg Observatory in Bergedorf, Germany
Centaur comet with orbital period of ~14.8 years

 

Orbit (from Minor Planet Center, MPEC 2021-P47)

 

  29P/Schwassmann-Wachmann                                                     
Epoch 2021 July 5.0 TT = JDT 2459400.5                                         
T 2019 Mar. 26.71300 TT                                 Rudenko                
q   5.7691551            (2000.0)            P               Q                 
n   0.06641981     Peri.   49.15488     +0.99219204     -0.03314924            
a   6.0386190      Node   312.37551     -0.03070814     +0.86942155            
e   0.0446234      Incl.    9.36679     +0.12088000     +0.49295771            
P  14.8                                                                        
From 36866 observations 1902 Mar. 4-2021 Aug. 5, mean residual 0".9.           

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

29P/Schwassmann-Wachmann                                         Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  04 51  +31 09   5.909   5.941    83M   Aur  12-14   61   37
2021-Sep-06  04 53  +31 17   5.911   5.865    87M   Aur  12-14   66   35
2021-Sep-11  04 54  +31 25   5.912   5.788    92M   Aur  12-14   70   34
2021-Sep-16  04 56  +31 33   5.913   5.711    96M   Aur  12-14   74   32
2021-Sep-21  04 56  +31 40   5.915   5.635   101M   Aur  12-14   78   31
2021-Sep-26  04 57  +31 47   5.916   5.560   106M   Aur  12-14   81   30
2021-Oct-01  04 57  +31 53   5.918   5.488   110M   Aur  12-14   82   28
2021-Oct-06  04 57  +31 59   5.919   5.417   115M   Aur  12-14   82   27

 

Comet Magnitude Formula

 

None, due to frequent outbursts.

 

29P/Schwassmann-Wachmann was discovered photographically on 1927 November 15 by German observing team Arnold Schwassmann and Arno Arthur Wachmann. The duo discovered 4 comets together, three short-period comets (29P/Schwassmann-Wachmann, 31P/Schwassmann-Wachmann, and 73P/Schwassmann-Wachmann) and a long-period comet shared with Leslie Peltier [C/1930 D1 (Peltier-Schwassmann-Wachmann)].

 

29P is one of the more enigmatic comets. It is always active and rarely fainter than 17th-18th magnitude. Multiple times per year outbursts occur resulting in a peak brightness that can reach 10th magnitude though most peaks fall in the 11th to 14th magnitude range. Richard Miles (Director of the British Astronomical Society’s Asteroids and Remote Planets Section) has published a series of papers on 29P and its outbursts. He found that as many as 6 active areas are producing outbursts on a nucleus with a rotation period of ~57-58 days.

29P is also considered a member of the Centaur population. Different organizations have different definitions for what constitutes a member of the Centaurs. The two most common definitions are from the Minor Planet Center (perihelion beyond the orbit of Jupiter and semi-major axis within the orbit of Neptune) and the Jet Propulsion Laboratory (semi-major axis between the orbits of Jupiter and Neptune). Both definitions would classify 29P as a Centaur.

 

29P has experienced two outbursts in recent weeks. An outburst of ~2 magnitudes was first observed by J.-F. Soulier on August 25 while a smaller ~1 magnitude outburst was reported by Patrick Wiggins and observers using the GROWTH India Telescope on September 4.

 

The comet is a morning object in Auriga and observable from both hemispheres. If you image 29P, please consider contributing to the British Astronomical Society’s (BAA) 29P monitoring program coordinated by Richard Miles. You can find more information at the BAA’s “Observing the outbursting comet 29P/Schwassmann-Wachmann” page ( https://britastro.org/node/18562 ) and at the BAA’s “Mission 29P” page ( https://britastro.org/node/25120 ).

 

C/2021 A1 (Leonard)

 

Discovered 2021 January 3 by Greg Leonard of the Catalina Sky Survey with the 1.5-m on Mount Lemmon
Dynamically old long-period comet

 

Orbit (from Syuichi Nakano, Nakano Note NK 4507)

 

   C/2021 A1 (Leonard)
Epoch 2022 Jan. 21.0 TT = JDT 2459600.5 
T 2022 Jan. 3.30026 TT                                  Nakano
q   0.6152393            (2000.0)            P               Q
z  -0.0000203      Peri.  225.09370     +0.63774801     +0.29159700
+/-0.0000023      Node   255.89553     +0.72790120     -0.53082217
e   1.0000125      Incl.  132.68637     -0.25186767     -0.79573803
From 1016 observations 2020 Apr. 11-2021 July 22, mean residual 0".52.
  (1/a)org.= +0.000525, (1/a)fut.= -0.000080 (+/-0.000002), Q= 8.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

C/2021 A1 (Leonard)                                               Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  10 54  +41 25   2.283   3.060    33E   UMa  14.0     9    0
2021-Sep-06  10 57  +40 44   2.214   2.974    34M   UMa  13.8     8    0
2021-Sep-11  11 01  +40 05   2.144   2.881    35M   UMa  13.6    10    0
2021-Sep-16  11 05  +39 27   2.073   2.782    37M   UMa  13.5    13    0
2021-Sep-21  11 09  +38 51   2.002   2.676    39M   UMa  13.2    15    0
2021-Sep-26  11 14  +38 16   1.930   2.564    41M   UMa  13.0    18    0
2021-Oct-01  11 18  +37 43   1.858   2.445    43M   UMa  12.8    21    0
2021-Oct-06  11 23  +37 12   1.784   2.319    46M   UMa  12.5    24    0

 

Comet Magnitude Formula (from ALPO and COBS data)

 

m1 = 8.7 + 5 log d + 8.0 log r

 

The 10th comet to bear Catalina Sky Survey astronomer Greg Leonard’s name was found on 2021 January 3 with the Mount Lemmon 1.5-m reflector. (Greg would discover two additional comets since then.) C/2021 A1 (Leonard) was around magnitude 19 and located at a distance of 5.1 au from the Sun at discovery. Pre-discovery observations from Mount Lemmon and PANSTARRS have been found back to April 2020 (when the comet was 7.5 au from the Sun).

 

C/2021 A1 has the potential to become a nice object at the end of the year due to a relatively small perihelion of 0.62 au on 2022 January 3, a close approach to within 0.233 au from Earth on December 12, and a phase angle that reaches a maximum of 160 degrees at the time of close approach which may result in a few magnitudes of enhanced brightness due to forward scattering of light by cometary dust. Working against it are difficult observing circumstance due to a small solar elongation at the time of maximum brightness (minimum elongation of 15 deg) resulting in the possibility that the comet may be too faint to be seen while so close to the Sun.

 

Based on CCD photometry submitted to the Minor Planet Center, COBS, and the ALPO, C/2021 A1 appeared to brighten at a rapid rate of 2.5n ~ 16 through 2020, but then slowed down drastically to a rate closer to 2.5n ~ 6 for most of 2021. Observations have been scarce lately as the comet passes through solar conjunction, though well north of the Sun. Surprisingly the few observations submitted to the COBS site in late July and August (by observers Harri Kiiskinen, Steffan Fritsche, and Michael Lehmann) suggest that Leonard may have started a new rapid brightening phase. The most recent observations from Harri Kiiskinen on August 29 and 30 and September 1 and 4 had the comet at magnitude 13.8-14.3. As Leonard moves further out of the glare of dawn, hopefully we’ll get a better idea of its current brightening rate.

 

Assuming the recent Kiiskinen magnitudes are correct and a conservative 2.5n ~ 8 brightening rate, C/Leonard is a should reach 12-13th magnitude by the end of September. As has been the case for months now, Leonard is a far northern object in Ursa Major meaning it is still not visible from the southern hemisphere. Imagers and now large aperture visual observers are strongly encouraged to monitor C/2021 A1 as it approaches its January perihelion and beyond.

 

C/2021 O3 (PANSTARRS)

 

Discovered 2021 July 26 by Pan-STARRS with the 1.8-m Pan-STARRS1 1.8-m on Haleakala

 

Orbit (from Syuichi Nakano, private email)

 

   C/2021 O3 (PANSTARRS)
T 2022 Apr. 21.25384 TT                                 Nakano
q   0.2869675            (2000.0)            P               Q
                   Peri.  299.99950     -0.56870972     -0.81190292
                   Node   189.07502     +0.64626694     -0.54021337
e   1.0            Incl.   56.70951     -0.50883032     +0.22132140
From 90 observations 2021 July 26-Aug. 5.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

C/2021 O3 (PANSTARRS)                                             Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2021-Sep-01  22 59  +27 13   3.891   3.028   144M   Peg  18.2    77   23
2021-Sep-06  22 53  +26 43   3.831   2.949   146E   Peg  18.1    77   23
2021-Sep-11  22 48  +26 07   3.771   2.876   148E   Peg  18.0    76   24
2021-Sep-16  22 42  +25 23   3.711   2.812   149E   Peg  17.9    75   25
2021-Sep-21  22 36  +24 33   3.650   2.755   148E   Peg  17.8    75   25
2021-Sep-26  22 30  +23 36   3.589   2.706   146E   Peg  17.7    74   26
2021-Oct-01  22 25  +22 33   3.527   2.665   144E   Peg  17.6    73   27
2021-Oct-06  22 19  +21 25   3.465   2.631   140E   Peg  17.5    71   29

 

Comet Magnitude Formula (based on data submitted to the COBS and the MPC)

 

m1 = 11.2 + 5 log d + 8 log r

 

C/2021 O3 (PANSTARRS) was first seen on July 26 at 19th magnitude by the Pan-STARRS1 1.8-m Ritchey-Chretien on Haleakala. Though currently 4.2 au from the Sun, C/2021 O3 will get a lot closer to the Sun at perihelion. With a short published observational arc, the comet appears to be a long-period comet though it will be some weeks (unless pre-discovery observations are found) before we know whether it is dynamically old or new.

 

Perihelion occurs on 2022 April 21 at 0.29 au. We still don’t have any information on this comet’s brightening rate as few observations have been published by the MPC or submitted to COBS or the ALPO. Regardless, C/2021 O3 will experience some of the same observational issues as C/2021 A1 (Leonard). On the plus side, PANSTARRS will reach a relatively large phase angle though not as large as Leonard (only ~136 vs 160 deg). PANSTARRS will also be located at very small solar elongations near perihelion which will make it a VERY difficult object to observe until a few weeks after perihelion and then only for northern observers.

 

Like last month, C/2021 O3 is riding high in Pegasus in the evening for northern observers, but not so far north southern observers won’t also be able to observe it. Though observations will be limited to imaging as it is expected to be around 17-18th magnitude this month.

 

Southern hemisphere observers should be able to follow PANSTARRS till the end of the year when the comet could be around 15-16th magnitude. Northern hemisphere observers will be able to follow it for another month or two till mid-February when it could be as bright as 13-14th magnitude. The comet will then spend the next two and a half months within 20 deg of the Sun.

 

The analysis that follows assumes the comet will not disintegrate. If it turns out to be dynamically new, its current brightness suggests an intrinsically faint object that may be prone to disintegration.

 

The comet’s orbit is aligned in such a way that the comet will be mainly a northern hemisphere object except for a week or so centered on perihelion. On the date of perihelion C/2021 O3 will be an evening object located only 16 deg from the Sun. Northern hemisphere observers (for +40N) will not be able to observe it at that time as it will still be 7 deg below the horizon at the start of nautical twilight. It will be observable from the southern hemisphere (-40S) when it will be at an elevation of 5 deg at the start of nautical twilight and only 1 deg below the horizon at the start of astronomical twilight. If the comet brightens at a 2.5n ~ 10 from now till perihelion, it could be a 4th magnitude object. If its rate of brightening is 2.5n ~ 8, it will be fainter at 6-7th magnitude. Either way this will be a difficult observation.

 

The comet becomes observable in a dark sky (after the end of astronomical twilight) by the first few nights of May. This is around the time of maximum phase angle (135 deg) which may provide a 1-2 magnitude boost in brightness. Still, we are talking about an object that may only be around 3rd-6th magnitude and still located ~20 deg from the Sun. Though it will be fading fast, the comet will quickly move north and circumpolar by mid-May.

 

Like Leonard, imagers are highly encouraged to observe PANSTARRS over the coming months.

 

New Discoveries, Recoveries and Other Comets in the News

 

Remembering Carolyn Shoemaker (1929-2021) – August brought the sad news that Carolyn Shoemaker passed away. I can’t hope to do Carolyn justice so instead I ask that you read the two wonderful pieces posted by David Levy at Sky & Telescope website and by the United States Geological Survey.

 

https://skyandtelesc...aker-1929-2021/
https://www.usgs.gov...maker-1929-2021

 

New Comet Numberings (Ref: WGSBN Bull. 1 #6)

 

425P/2005 W3   = P/2021 O2 (Kowalski)
424P/2012 S2   = P/2021 L5 (La Sagra)
423P/2008 CL94 = P/2021 A12 (Lemmon)
422P/2006 S4   = P/2021 L1 (Christensen)
421P/2009 U4   = P/2020 H10 (McNaught)

 

P/2021 Q5 (ATLAS) – The "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) project discovered a 17th magnitude short-period comet on August 29 with a 0.5-m f/2 Schmidt on Haleakala, Hawaii. Perihelion was only a few days ago on August 30 at 1.23 au. The current orbit is still uncertain but suggests the comet had a close approach within 0.06-0.25 au of Jupiter in late 2018 or early 2019. The comet may have had a very different orbit prior to that close approach explaining why it was not seen previously. The current orbit gives an orbital period of 5.6-years but that may change as the orbit is refined.

 

There are questions as to this comet’s current brightness. Most CCD observations submitted to COBS have the comet between magnitude 15 and 18. Most also measured a coma smaller than 10”. Michael Jager found a much larger coma at 130-140” but still estimated the comet at a faint 17th magnitude. J. J. Gonzalez reported a visual detection of C/2021 Q5 at magnitude 11.5 with a coma diameter of 4’. Hopefully further visual attempts will be made to confirm the true brightness of this object. If J. J.’s brightness is confirmed, I will post an update to our CloudyNights forum page. [Ref: MPEC 2021-R98, CBET 5029]

 

C/2021 Q4 (Fuls) – D. Carson Fuls discovered the 5th comet to be named after him. C/2021 Q4 was found on 2021 August 26 at 19-20th magnitude with the Mount Lemmon 1.5-m. Several pre-discovery images were found back to April 2020 when the comet was 22nd magnitude. Perihelion won’t be till 2023 June 10 at 7.56 au when the comet will be slightly brighter at 19th magnitude. [Ref: MPEC 2021-Q102, CBET 5028]

 

C/2021 Q3 (ATLAS) – A 19th magnitude object first detected by the ATLAS survey on 2021 August 26 was found to be cometary in follow-up images taken by Pan-STARRS. C/2021 Q3 has a ~600 +/- 200 year orbit with a distant perihelion on 2022 January 23 at 5.20 au. It will likely get no brighter than 18th magnitude. [Ref: MPEC 2021-Q97, CBET 5027]

 

P/2021 Q2 = P/2011 A2 (Scotti) – B. T. Bolin of the Zwicky Transient Facility used the 1.2-m Schmidt on Mount Palomar to recover this short-period comet on 2021 August 20, 23, 24, and 25 at 18th magnitude. Perihelion will be later this year on December 2 at 1.55au. P/Scotti was discovered by former ALPO Comets Section Assistant Recorder Jim Scotti on 2011 January 11 with the Spacewatch 0.9-m on Kitt Peak. During its discovery apparition it reached 16-17th magnitude. This time around it should peak at 17th magnitude. [Ref: MPEC 2021-Q69, CBET 5026]

 

P/2021 Q1 = P/2014 W12 (Gibbs) – E. Schwab (Egelsbach, Germany) with D. Koschny, M. Micheli, and E. Petrescu used a 0.8-m f/3 Schmidt telescope at Calar Alto to recover this comet at 19-20th magnitude on 2021 August 16-17. P/Gibbs peaked at 16-17th magnitude in 2014. The comet already passed through perihelion on 2021 May 14 at 1.67 au and is currently 2 magnitudes fainter than its brightness in 2014 would suggest. S. Nakano found a night of pre-discovery observations from the Catalina Sky Survey taken in 2008. [Ref: MPEC 2021-Q47, CBET 5025]

 

P/2021 P5 = P/2015 Q1 (Scotti) – Jim Scotti had another one of his comets recovered last month. F. Kugel recovered 20th magnitude P/2015 Q1 = P/2021 P5 on images taken on 2021 August 2, 3, 7, 8, and 16. J. Maikner also reported observations from 2021 June 5 and August 5 and J.-F. Soulier from August 8. Kugel used a 0.4-m f/2.8 reflector, Maikner used a 0.30-m f/3.8 Riccardi-Honders, and Soulier a 0.25-m f/3.5 Newtonian reflector. The comet reached 15-16th magnitude in 2015/16. This time is may brighten to 18th magnitude around the time of its 2022 February 13 perihelion at 1.81 au. [Ref: MPEC 2021-Q75]

 

C/2021 P4 (ATLAS) – The "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program found this 19th magnitude comet on 2021 August 10 with their 0.5-m f/2 Schmidt reflector on Haleakala, Hawaii. Perihelion occurs on 2022 July 29 at 1.08 au. Unfortunately, the comet will be located on the other side of the Sun at a geocentric range of ~2 au and low solar elongation. An assumed photometric index of 2.5n = 10 only brings C/2021 P4 up to 11th magnitude at perihelion. Too bad perihelion wasn’t in early March when a close approach to within 0.1 au of Earth would have occurred resulting in a 4-5th magnitude comet racing through the opposition sky. Oh well, perhaps it will be a better object for Earth-based observers when it returns in ~1700 years. [Ref: MPEC 2021-Q42, CBET 5024]

 

P/2021 P3 (PANSTARRS) – Now begins the Pan-STARRS portion of our broadcast as the next few objects were either recovered or discovered by Pan-STARRS. P/2021 P3 is a short-period comet with an orbital period of 9.3-years and perihelion back on 2021 May 28 at 2.91 au. It is unlikely to get any brighter than at its 2021 August 11 discovery when is was 20th magnitude. [Ref: MPEC 2021-Q29, CBET 5022]

 

C/2021 P2 (PANSTARRS) – Pan-STARRS first found this 21st magnitude object on 2021 August 7 followed by pre-discovery observations from 2021 June 19. With a distant 5.07 au perihelion on 2023 January 23, C/2021 P2 will be near peak brightness for ~2 years. Unfortunately, that peak brightness will be a faint 19th magnitude. [Ref: MPEC 2021-Q28, CBET 5023]

 

C/2021 P1 (PANSTARRS) – Pan-STARRS found another distant (q = 4.37 au) and faint (20-21st magnitude) comet on August 9 with pre-discovery observations found on July 14, 21 and August 4. Perihelion will occur on 2022 June 1. The comet is not expected to get much brighter than magnitude 20. [Ref: MPEC 2021-Q2, CBET 5020]

 

P/2021 N4 - Y. Ramanjooloo (University of Hawaii) reported to the CBAT the discovery of a 21-22nd magnitude Main Belt comet in images taken on 2021 July 8 and August 9 with the Pan-STARRS1 1.8-m reflector on Haleakala. Pre -discovery observations from two nights in October and November 2016 have been found by Pan-STARRS. Perihelion occurs on 2021 August 28 at 2.30 au. Being a Main Belt comet, it won’t get far from the Sun with a “shallow” aphelion of only 3.79 au. The comet has likely already peaked in brightness. Unlike other Main Belt comets, no name was given to this object since its orbit is obviously asteroidal. It will be interesting to see if names will be withheld from future Main Belt comets. [Ref: MPEC 2021-Q1, MPEC 2021-Q96, CBET 5019]

 

P/2021 M1 = P/2008 QP20 (LINEAR-Hill) – This short-period comet was co-discovered by the LINEAR survey and the ALPO’s very own Solar Section Coordinator Rik Hill. It is the second comet to be named LINEAR-Hill, the other being the split comet P/2004 V5. During its discovery apparition in 2008, this P/LINEAR-Hill peaked at 16th magnitude. Its recovery was made by the Pan-STARRS program over seven nights in June, July, and August of this year. The current apparition sees perihelion on 2022 January 2 at 1.81 au and a peak brightness of only ~19th magnitude. P/LINEAR-Hill has an orbital period of 6.7 years. [MPEC 2021-Q68]

 

P/2021 K4 = P/2019 A7 (PANSTARRS) – M. Micheli reported to the CBAT that H. Hsieh and D. Faes used the 8.1-m Gemini South telescope on Cerro Pachon in Chile to recover this Main Belt comet on 2021 May 17 and June 13 at 22nd magnitude. This object reached 19th magnitude in 2019 when it was already a year after perihelion. It is now after aphelion and hence why a comet that was discovered in 2019 can be recovered only ~2 years later. Its next perihelion will be on 2023 September 12 at 2.67 au. If it brightens like it did in 2019, it may again peak around 19th magnitude in late 2023 into early 2024. [Ref: CBET 5010]

 

P/2021 L6 = P/2017 S5 (ATLAS) – M. Micheli also reported to the CBAT that H. Hsieh, S. Margheim, and L. Magill used the 8.1-m Gemini South telescope on Cerro Pachon in Chile to recover another Main Belt comet. P/2021 L6 was recovered on 2021 June 9, 12 and 13 at 24th magnitude. This object reached 17th magnitude in 2017. The next perihelion will be on 2023 March 19 at 2.17 au though it may only brighten to 19th magnitude during this return. [Ref: CBET 5011]

 

As always, the Comet Section is happy to receive all comet observations, whether textual descriptions, images, drawings, magnitude estimates, or spectra. Please send your observations via email to the Comets Section < comets @ alpo-astronomy .org >, Comets Section Coordinator Carl Hergenrother < carl.hergenrother @ alpo-astronomy .org > and/or Comets Section Acting Assistant Coordinator Michel Deconinck < michel.deconinck @ alpo-astronomy .org >.

 

Thank you to everyone who contributed to the ALPO Comets Section!

 

Stay safe and enjoy the sky!
- Carl Hergenrother


Edited by Carl H., 06 September 2021 - 07:02 PM.

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#2 Carl H.

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Posted 08 September 2021 - 04:23 PM

Chris Wyatt observed 8P/Tuttle at magnitude 9.0 with a 16" F/4 reflector at 59x on September 7.77 UT. He measured a moderately condensed 2.8' coma.

 

Chris was not successful in visually detecting newly discovered P/2021 Q5 (ATLAS) down to a limiting magnitude of 15.5. 



#3 Carl H.

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Posted 12 September 2021 - 01:40 PM

A few recent measurements of fainter comets made with iTelescopes.

 

   2017K2  2021 09 10.15  V 13.3 U4 10.6R 5a600   1.4       1.2m 20 ICQ xx HER02 Carl Hergenrother
   2020S3  2021 08 31.65  C 17.1 U4 50.0Y 5A200   0.7       3.1m250 ICQ xx HER02 Carl Hergenrother
   2021O3  2021 09 08.27  C 18.7 U4 50.0Y 5A200   0.3               ICQ xx HER02 Carl Hergenrother

 

C/2021 O3 (PANSTARRS) is small and condensed but really hasn't brightened since discovery.



#4 emh52

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Posted 19 September 2021 - 10:03 AM

This is 6p/Arrest about to transit M20 on Sept 18 as discussed in Carl's report. This a T11 iTelescope stack of 3x180 sec, the window to photograph from NM was only 16 min due to the comets low altitude. This is a stack of 3 x 180 sec. I tried to catch the comet coming out the other side of M20 from Siding Spring but had equipment issues, so no photo.

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  • CN 6p d'arrest M20.jpg

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#5 Octans

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Posted 29 September 2021 - 12:46 AM

Hearing that 29P has had a series of 4 outbursts and has now brightened substantially to magnitude 11: https://groups.io/g/...305311465453977




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