Comet Section

December 3, 2021 – ALPO Comet News for December 2021

Summary

It is now or never for C/2021 A1 (Leonard). Currently magnitude 6.5, Leonard has the potential to become a few magnitudes brighter as it passes 0.23 au from Earth on December 12. Complicating any forecast of how bright or observable it might get are a very low solar elongation (down to 15 degrees), uncertainty in the effect of dust forward scattering to enhance Leonard’s brightness, and signs that the comet is fading or perhaps even breaking up. This is an object well worth watching in the morning sky from the northern hemisphere during the first half of the month and in the evening sky during the second half of December (though at that time it will be much easier to observe from the southern hemisphere).

Other comets brighter than 10th magnitude in December include C/2019 L3 (ATLAS), 19P/Borrelly, and 67P/Churyumov-Gerasimenko.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

November 7, 2021 – ALPO Comet News for November 2021

Summary

After an exciting 2020 for comets, 2021 seemed to be a bit of a letdown. Well, it may have taken most of the year to get going, but 2021 is finally picking up steam. We now have three comets brighter than magnitude 10. C/2021 A1 (Leonard) may brighten to the verge of naked eye visibility (for those under very dark skies) by the end of the month. It should get even brighter next month when it could reach 4th magnitude or perhaps even brighter. C/2019 L3 (PANSTARRS) and 67P/Churyumov-Gerasimenko will be around magnitude 9 this month.

If you’ve never observed 29P/Schwassmann-Wachmann before, this is a great time to start. The Centaur comet has experienced a succession of outbursts since late September. As a result, it is brighter than it’s been in years with visual observers placing it between magnitude 10 and 11.

Two recently discovered comets have the potential to be nice small telescope objects when they arrive at perihelion over the next few years. C/2021 S3 (PANSTARRS) may reach 8th magnitude in 2024 while C/2021 T4 (Lemmon) could be a 9th magnitude object in 2023.

Comets Section News

From October 1 through the first week of November, the ALPO Comets Section received 125 visual and CCD magnitude measurements and 80 images and/or sketches from Dan Bartlett, Michel Besson, Denis Buczynski, Dan Crowson, Michel Deconinck, J. J. Gonzalez, Christian Harder, Carl Hergenrother, Eliot Herman, Gianluca Masi, Martin Mobberley, Mike Olason, Ludovic Prebet, Efrain Morales Rivera, Chris Schur, Tenho Tuomi, Dennis Wilde, and Chris Wyatt of the following comets: C/2021 K1 (ATLAS), C/2021 A1 (Leonard), C/2020 T2 (Palomar), C/2020 F5 (MASTER), C/2019 T4 (ATLAS), C/2019 LD2 (ATLAS), C/2019 L3 (ATLAS), C/2019 F1 (ATLAS-Africano), C/2017 K2 (PANSTARRS), 433P/(248370) 2005 QN173 ,429P/LINEAR-Hill, 424P/La Sagra, 284P/McNaught, 246P/NEAT, 230P/LINEAR, 179P/Jedicke, 132P/Helin-Roman-Alu, 119P/Parker-Hartley, 113P/Spitaler, 104P/Kowal, 97P/Metcalf-Brewington, 94P/Russell, 67P/Churyumov- Gerasimenko, 57P/du Toit-Neujmin-Delporte, 29P/Schwassmann-Wachmann, 19P/Borrelly, 8P/Tuttle, 7P/Pons-Winnecke, 6P/d’Arrest, and 4P/Faye.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

October 4, 2021 – ALPO Comet News for October 2021

Summary

Magnitude 9 to 10 may not be everyone’s idea of “bright” when it comes to comets. After months of no comets getting brighter than 10th magnitude, we finally have a few objects breaking the 10th magnitude barrier. The target of the European Space Agency’s Rosetta mission, 67P/Churyumov-Gerasimenko may brighten to around magnitude 9 this month. It will be observable from both hemispheres in the morning sky. 8P/Tuttle will start the month around 8-9th magnitude but is limited to southern hemisphere observers. C/2019 L3 (PANSTARRS) could become brighter than magnitude 10 though it will mainly be a northern object.

29P/Schwassmann-Wachmann experienced 4 outbursts in quick succession in late September. As a result, it is brighter than it has become in years with visual observers placing it between magnitude 10 and 11.

We continue to watch C/2021 A1 (Leonard) develop as it heads towards a December encounter with Earth. Recent observations show a rapid brightening trend, so imagers and large aperture visual observers are encouraged to observe it this month as it may brighten to magnitude 11 by the end of the month.

Comets Section News

During September, the ALPO Comets Section received 51 images and/or sketches from Dan Bartlett, Denis Buczynski, Eliot Herman, Gianluca Masi, Martin Mobberley, Uwe Pilz, Efrain Morales Rivera, Gregg Ruppel, and Chris Schur and 67 visual and CCD magnitude measurements from Michel Deconinck, J. J. Gonzalez, Mike Olason, and Chris Wyatt of the following comets: P/2021 Q5 (ATLAS), C/2021 O3 (PANSTARRS), C/2021 A1 (Leonard), C/2020 T2 (Palomar), C/2020 PV6 (PANSTARRS), C/2020 F5 (MASTER), C/2019 O3 (PANSTARRS), C/2019 L3 (ATLAS), C/2019 F1 (ATLAS-Africano), C/2018 U1 (Lemmon), C/2020 T2 (PANSTARRS), C/2017 K2 (PANSTARRS), 284P/McNaught, 193P/LINEAR-NEAT, 106P/Schuster, 67P/Churyumov-Gerasimenko, 29P/Schwassmann-Wachmann, 19P/Borrelly, 15P/Finlay, 8P/Tuttle, 7P/Pons-Winnecke, 6P/d’Arrest, and 4P/Faye.

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 and dedicated comet hunters for their discoveries, and all of the observers who volunteer their time to adding to our knowledge of these amazing objects.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

September 6, 2021 – ALPO Comet News for September 2021

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.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

August 5, 2021 – ALPO Comet News for August 2021

Summary

July saw the discovery of 9th magnitude C/2021 O1 (Nishimura), though the comet was located so close to the Sun that few have been able to observe it. While we are still waiting for a comet to brighten into an easy-to-observe object for small apertures, a number of fainter comets are visible in the magnitude 10-13 range for imagers and large aperture visual observers. A recent discovery, C/2021 O3 (PANSTARRS), is currently around 18-19th magnitude but may brighten into a nice binocular object early next year.

Comets Section News

The ALPO’s Annual Conference will be held virtually on Friday and Saturday, August 13-14. Each day is packed with talks about various aspects of Solar System observing. The Comets Section will be presenting two talks. One will be an overview of the past year’s comet observations. The second talk will be on a slightly different topic, Solar System numismatics (i.e., Solar System objects, including comets, on coins and medals). The meeting is free and more information on the conference and how to watch can be found on the ALPO web site at https://alpo-astronomy.org/.

During July, the ALPO Comets Section received 27 images and/or sketches from Michel Deconinck, Carl Hergenrother, Martin, Mobberley, and Mike Olason of the following comets: 4P/Faye, 7P/Pons-Winnecke, 10P/Tempel, 15P/Finlay, 19P/Borrelly, 47P/Ashbrook-Jackson, 106P/Schuster, C/2017 K2 (PANSTARRS), C/2017 Y2 (PANSTARRS), C/2018 U1 (Lemmon), C/2019 K7 (Smith), C/2019 T3 (ATLAS), C/2019 T4 (ATLAS), C/2019 U5 (PANSTARRS), C/2020 F2 (ATLAS), C/2020 H5 (Robinson), C/2020 K1 (PANSTARRS), C/2020 M5 (ATLAS), C/2020 O2 (Amaral), C/2020 PV6 (PANSTARRS), C/2020 T2 (Palomar), C/2021 A1 (Leonard), C/2021 O1 (Nishimura).

The Section also received 82 visual and CCD magnitude measurements from Michel Deconinck, J. J. Gonzalez, Carl Hergenrother, Mike Olason, and Chris Wyatt of comets 4P/Faye, 7P/Pons-Winnecke, 10P/Tempel, 15P/Finlay, 19P/Borrelly, 67P/Churyumov-Gerasimenko, 106P/Schuster, 246P/NEAT, C/2017 K2 (PANSTARRS), C/2018 U1 (Lemmon), C/2019 F1 (ATLAS-Africano), C/2019 L3 (ATLAS), C/2019 T4 (ATLAS), C/2020 F5 (MASTER), C/2020 J1 (SONEAR), C/2020 PV6 (PANSTARRS), C/2020 T2 (Palomar), C/2021 A1 (Leonard), and C/2021 O1 (Nishimura).

In addition to observations submitted to the ALPO, we also occasionally use data from other sources to augment our analysis. We acknowledge with thanks comet observations submitted to the International Comet Quarterly, Minor Planet Center, COBS Comet Observation Database, and our own ALPO contributors used in this report.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

July 8, 2021 – ALPO Comet News for July 2021

Summary

We are still in the midst of a bright comet drought. The brightest comets of July should be around magnitude 10.0. These include two comets that ranked among the “brightest” last month, C/2020 T2 (Palomar) and 7P/Pons-Winnecke. Joining them around the magnitude 10.0 level will be another short-period comet, 15P/Finlay, which should reach its brightest at the end of July into early August. Between 11^th and 13^th magnitude are a number of other comets such as 4P/Faye, 8P/Tuttle, C/2017 K2 (PANSTARRS), and C/2019 L3 (ATLAS). Imagers are encouraged to continue monitoring inbound C/2021 A1 (Leonard). While this comet still has the potential to be a notable object at the end of the year, that hope is fading as the comet has been slow to brighten. Among newly discovered objects, C/2014 UN271 (Bernardinelli-Bernstein) ranks as one of the most interesting discoveries in some time. This object is still 10 years away from an extremely large perihelion distance of 10.95 au. Bernardinelli-Bernstein has already been imaged going back to 2014 and it is possible modestly equipped imagers may be able to follow it as an active object for another 20 years!

Comets Section News

Since June 1, the ALPO Comets Section received 15 images and/or sketches from John Chumack, Michel Deconinck, Jim Filipski, Carl Hergenrother, Martin, Mobberley, Mike Olason, John D. Sabia, and Tenho Tuomi of the following comets: 4P/Faye, 6P/d’Arrest, 7P/Pons-Winnecke, 8P/Tuttle, 15P/Finlay, 57P/du Toit-Neujmin-Delporte, 108P/Schuster, 246P/NEAT, C/2020 J1 (SONEAR), C/2020 T2 (Palomar), C/2021 A1 (Leonard), C/2021 D2 (ATLAS), P/2021 J3 (ATLAS), and an oldie but goodie of C/1975 V1 (West).

Also since June 1, the Section has received 58 magnitude measurements from Michel Deconinck, J. J. Gonzalez, Carl Hergenrother, and Chris Wyatt of comets 7P/Pons-Winnecke, 10P/Tempel, 15P/Finlay, 67P/Churyumov-Gerasimenko, 117P/Helin-Roman-Alu, 246P/NEAT, C/2017 K2 (PANSTARRS), C/2018 U1 (Lemmon), C/2019 F1 (ATLAS-Africano), C/2019 L3 (ATLAS), C/2019 T4 (ATLAS), C/2020 F5 (MASTER), C/2020 J1 (SONEAR), C/2020 R4 (ATLAS), C/2020 S3 (Erasmus), C/2020 T2 (Palomar), and C/2021 A1 (Leonard).

In addition to observations submitted to the ALPO, we also occasionally use data submitted to other sources for our analysis. We acknowledge with thanks the comet observations from the International Comet Quarterly, the Minor Planet Center, the COBS Comet Observation Database, and our own ALPO contributors used in this report.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

June 3, 2021 – ALPO Comet News for June 2021

Summary
Comets C/2020 T2 (Palomar) and 7P/Pons-Winnecke should vie for the title of brightest comet of June though they should only reach magnitude 10.0. While June won’t see any “bright” comets, there are a large number of fainter objects, in addition to the aforementioned comets, between magnitudes 10 and 13. These fainter objects include some low numbered periodic comets (4P/Faye, 8P/Tuttle, 10P/Tempel, and 15P/Finlay) and long period comets C/2019 L3 (ATLAS), C/2020 J1 (SONEAR), and C/2020 R4 (ATLAS). C/2021 A1 (Leonard) is still inbound and has the potential to be a notable object at the end of the year, though its lack of recent brightening is concerning.

Comets Section News
During the month of May 2021, the ALPO Comets Section received 32 images and/or sketches from Denis Buczynski, John Chumack, Carl Hergenrother, Martin, Mobberley, Mike Olason, Gregg Ruppel, John D. Sabia, and Chris Schur of the following comets: 4P/Faye, 6P/d’Arrest, 7P/Pons-Winnecke, 8P/Tuttle, 10P/Tempel, 15P/Fnlay, 17P/Holmes, 28P/Neujmin, 57P/du Toit-Neujmin-Delporte, 67P/Churyumov-Gerasimenko, 117P/Helin-Roman-Alu, C/2017 K2 (PANSTARRS), C/2019 K7 (Smith), C/2020 H5 (Robinson), C/2020 S1 (SONEAR), C/2020 R4 (ATLAS), C/2020 S3 (Erasmus), C/2020 T2 (Palomar), C/2021 A1 (Leonard), C/2021 A9 (PANSTARRS), and C/2021 E3 (ZTF).

On the magnitude front, J. J. Gonzalez, Carl Hergenrother, and Chris Wyatt submitted 43 visual and CCD/CMOS brightness measurements of comets 7P/Pons-Winnecke, 117P/Helin-Roman-Alu, 246P/NEAT, C/2017 K2 (PANSTARRS), C/2018 U1 (Lemon), C/2019 F1 (ATLAS-Africano), C/2019 T4 (ATLAS), C/2020 F5 (MASTER), C/2020 J1 (SONEAR), C/2020 R4 (ATLAS), C/2020 T2 (Palomar), and C/2021 A1 (Leonard).

The Comets Section Image Gallery (https://alpo-astronomy.org/gallery3/index.php/Comet-Images-and-Observations) also reached a milestone in May when the number of images/sketches passed the 6000 mark. The next milestone is the total number of different comets represented in the Gallery. We are only 4 comets away from having images of 600 comets.

We plan on publishing our analysis of the bright comets of 2019 in an upcoming issue of the Journal of the ALPO. If you have any comet observations from 2019, especially for comets 260P/McNaught, C/2018 N2 (ASSASN), C/2018 W2 (Africano), and C/2018 Y1 (Iwamoto), please consider sending them to the Comets Section at comets@alpo-astronomy.org. We would like to thank Jef De Wit, Uwe Pilz, and Michael Rosolina who recently contributed sketches of 2019’s brighter comets.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

May 6, 2021 – ALPO Comet News for May 2021

C/2020 R4 (ATLAS) finished April a little brighter than expected due to a small outburst. This month should see the comet fade from 8-9th magnitude to 11-12th magnitude. While no other comets are expected to be brighter than 10th magnitude this month, there are several slightly fainter objects at 11-12th magnitude.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

April 3, 2021 – ALPO Comet News for April 2021

As announced in the Spring 2021 issue of the Journal of the ALPO, Michel Deconinck has graciously accepted to serve as Acting Assistant Coordinator of the ALPO Comets Section. Michel is an avid observers and master sketcher of not just comets but many astronomical phenomena. Two of his sketches are included in the PDF version of this month’s Report. Please join me in welcoming Michel to the ALPO team!

Two comets, C/2020 R4 (ATLAS) and C/2021 D1 (SWAN) reached 9th magnitude in March. While SWAN should now be fainter than magnitude 10.0 and fading, C/2020 R4 (ATLAS) will continue to brighten to about magnitude 8.5 as it passes 0.46 au from Earth on April 23. A number of fainter comets are also visible for large aperture visual observers including 7P/Pons-Winnecke which is brightening to a 11th magnitude maximum in June/July. This marks 7P’s 25th observed return and is part of a run of low numbered periodic comets returning in 2021.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

March 5, 2021 – ALPO Comet News for March 2021

Not sure if we’ll have any comets brighter than 10th magnitude this month though there are two contenders. C/2020 R4 (ATLAS) may break the magnitude 10 barrier at the end of March but this is uncertain as the comet has not been observed since early January (due to being too close to the Sun). Newly discovered C/2021 D1 (SWAN) is close to the magnitude 10 barrier but it appears likely that it is as bright as it will get at 10-11th magnitude. In the meantime, there are many other comets between magnitude 10 and 13 that are good targets for CCD imagers and large aperture visual observers. Though still around 18th magnitude, imagers are encouraged to monitor C/2020 A1 (Leonard) which may become a nice object in December.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum. All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

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