Comet Section        

 
 

April 1, 2020 – ALPO Comet News for April 2020

Much has changed since over the past month, not only with the state of the world, but with comets. C/2019 Y4 (ATLAS) has asserted itself as the comet of the moment. Currently between 7th and 8th magnitude as April begins, the comet may become a borderline naked eye object under dark skies by the end of the month. It will be interesting to watch how it develops.

C/2019 Y4 isn’t the only object of interest. Both C/2017 T2 (PANSTARRS) and C/2019 Y1 (ATLAS) are brighter than 10th magnitude and CCD and large aperture visual observers are encouraged to watch fainter comets 88P/Howell, 210P/Christensen, 249P/LINEAR, and C/2019 U6 (Lemmon).

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum (https://www.cloudynights.com/topic/700215-alpo-comet-news-for-april-2020/). All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

 
 

March 3, 2020 – ALPO Comet News for March 2020

2020 was not predicted to be an exciting year for comets. Luckily some recent discoveries are making this a more interesting year. March will definitely see two comets brighter than 10th magnitude [C/2017 T2 (PANSTARRS) and C/2019 Y1 (ATLAS)] and possibly a third [C/2019 Y4 (ATLAS)]. All three are only visible from the northern hemisphere. This report also presents a number of fainter comets. While still faint in March, some of these may become bright enough for visual observers later in the year.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum (https://www.cloudynights.com/topic/696741-alpo-comet-news-for-march-2020/). All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

 
 

February 1, 2020 – ALPO Comet News for February 2020

Long period comet C/2017 T2 (PANSTARRS) continues to be well placed for northern observers in the evening sky at ~9th magnitude. Two recently announced discoveries, C/2019 Y1 (ATLAS) and C/2020 A2 (Iwamoto), are fainter (10-11th magnitude) but within range of visual observers with large apertures.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum (https://www.cloudynights.com/topic/692887-alpo-comet-news-for-february-2020/). All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

 
 

January 1, 2020 – ALPO Comet News for January 2020

Happy New Year and welcome to 2020!

The brightest comet as 2020 begins is long-period comet C/2017 T2 (PANSTARRS). It is possible that PANSTARRS will be the brightest comet of the year even though it is only predicted to peak around magnitude 8. This month, PANSTARRS is nicely placed for northern observers in the evening sky. CCD observers can observe interstellar visitor 2I/Borisov at 15-16th magnitude though it is likely to start fading. Another comet of interest to CCD imagers is short-period comet 289P/Blanpain which passes within 0.09 au of Earth this month. How bright this comet gets is uncertain as it is a faint, outburst prone object.

The monthly ALPO Comet News PDF can be found here. A shorter version of this report is posted on a dedicated Cloudy Nights forum (https://www.cloudynights.com/topic/688998-alpo-comet-news-for-january-2020/). All are encouraged to join the discussion over at Cloudy Nights.

- Carl Hergenrother

 
 

December 3, 2019 – ALPO Comet News for December 2019

C/2017 T2 (PANSTARRS) is well placed in the evening sky for northern observers and should become brighter than 10th magnitude this month. CCD imagers are encouraged to image a number of fainter comets this month. In particular, the following are of interest. Interstellar visitor 2I/Borisov will be at its best around 15th magnitude. December and January will see short-period comet 289P/Blanpain pass within 0.09 au of the Earth. How bright this comet gets is uncertain as it is a faint, outburst prone object. Speaking of outburst prone comets, the British Astronomical Society invites CCD photometrists to join their effort to monitor the outbursts of 29P/Schwassmann-Wachmann.

The monthly ALPO Comet News PDF can be found here. An edited version of this report is posted on the Cloudy Nights forum at (https://www.cloudynights.com/topic/685850-alpo-comet-news-for-december-2019/). Everyone is invited to join the discussion at our Cloudy Nights forum.

- Carl Hergenrother

 
 

November 2, 2019 – ALPO Comet News for November 2019

November finds us in-between bright comets. C/2018 W2 (Africano) is now too faint for small aperture telescopes while C/2017 T2 (PANSTARRS) is at least a month away from becoming an easy object. Fortunately it will continue to brighten over the next few months and should provide a nice target for much of the first half of 2020. CCD imagers are encouraged to keep a detector on interstellar comet 2I/Borisov which will be around 15-16th magnitude this month.

Other comets brighter than 13th magnitude this month include 29P/Schwassmann-Wachmann, 260P/McNaught, and C/2018 N2 (ASASSN). Fainter comets of interest include 289P/Blanpain and the aforementioned 2I/Borisov.

The monthly ALPO Comet News PDF can be found here. An edited version of this report is posted on the Cloudy Nights forum at (https://www.cloudynights.com/topic/682477-alpo-comet-news-for-november-2019/). Everyone is invited to join the discussion at our Cloudy Nights forum.

 
 

October 4, 2019 – ALPO Comet News for October 2019

I’m mixing things up a bit this month. The monthly ALPO Comet News are now be distributed as PDFs (link to this month’s PDF). A shorter version of this report is also posted on the Cloudy Nights forum. If you’d like to join in the discussion, I encourage you to visit our Cloudy Nights forum.

C/2018 W2 (Africano) starts the month around magnitude 8.5 though it will rapidly fade as the month progresses. C/2017 T2 (PANSTARRS) will still be 11th magnitude at the end of September but should replace Africano as the brightest observable comet. CCD observers can look forward to observing the first confirmed interstellar comet, 2I/2019 Q4 (Borisov). Other comets observable this month at brighter than 12th magnitude include 68P/Klemola, 260P/McNaught, and C/2018 N2 (ASASSN).

 
 

NEW BRIGHT COMET – C/2018 V1 (MACHHOLZ-FUJIKAWA-IWAMOTO)

2018-November-11

Wow, this is cool in so many ways!
Nowadays even comets that become bright are discovered months to years before perihelion and usually by professional surveys. The latest comet to be discovered is sort of a throwback to the old days of comet hunting. For starters, the comet was relatively bright at discovery (10th magnitude, though recent observations suggest it may have brightened to 7th or 8th magnitude). Also it was found by three independent amateurs and now shares all three of their names. And lastly, one of the discoverers is our very own former Comet Section Coordinator, Don Machholz, who found the comet visually!

C/2018 V1 (Machholz-Fujikawa-Iwamoto) has been officially announced on CBET 4569 and MPEC 2018-V151. The comet was found by all three discoverers within about 8 hours of each other. Don visually used a 0.47-m reflector at 113x while Fujikawa used a CCD + 120-mm-f.l. f/3.5 lens and Iwamoto used a 10-cm f/4.0 Pentax SDUF II telephoto lens and a Canon EOS 6D camera.

The comet may be experiencing an outburst. Hence, why it was suddenly discovered as a bright object by three observers within ~8 hours of each other. It brightness behavior is definitely suggestive of an outburst. It was reported by Machholz at magnitude 10.5 at discovery. J. J. Gonzalez saw the comet at magnitude 9.9 on Nov. 9.22 UT while Chris Wyatt saw it even brighter at 8.9 on Nov. 10.72 UT. Charles Morris just posted an estimate on comets-ml from last night (Nov. 11.55 UT) placing the comet closer to magnitude 7.5!

This is Don’s 12th discovery and first since C/2010 F4 after 746 hours of visual searching. His other discoveries include 96P/Machholz, 141P/Machholz, C/1978 R3 (Machholz), C/1985 K1 (Machholz), C/1988 P1 (Machholz), C/1992 F1 (Tanaka-Machholz), C/1992 N1 (Machholz), C/1994 N1 (Nakamura-Nishimura-Machholz), C/1994 T1 (Machholz) and C/2004 Q2 (Machholz). The comet is the seventh to bear Shigehisa Fujikawa’s name. He also independently discovered two comets in 1968, C/1968 N1 (Honda) and C/1968 H1 (Tago-Honda-Yamamoto). His other discoveries include C/1969 P1 (Fujikawa), C/1970 B1 (Daido-Fujikawa), C/1975 T1 (Mori-Sato-Fujikawa), C/1983 J1 (Sugano-Saigusa-Fujikawa), C/2002 X5 (Kudo-Fujikawa) and a rediscovery of comet 72P/Denning-Fujikawa. This is Masayuki Iwamoto’s second comet after C/2013 E2 (Iwamoto).

The comet marks the first visual comet discovery in almost exactly 8 years since the discovery of 332P/2010 V1 (Ikeya-Murakami). It is also the first comet to bear three names since C/2015 VL62 (Lemmon-Yeung-PanSTARRS) and the first to bear three amateur names in 24 years! Don was involved with that comet as well [C/1994 N1 (Nakamura-Nishimura-Machholz)].

The MPEC 2018-V151 orbit makes C/2018 V1 a long-period comet with perihelion on December 3 at 0.39 AU and inclination of 144 degrees. The comet was too close to the Sun to be seen until a few weeks ago. Unfortunately, it will drop back into the glare of the Sun in another week or two. After that the comet will not be visible to northern hemisphere observers. Southern hemisphere observers should be able to image the comet again starting next February. I say imaging since the comet will then be much further from the Sun and Earth at that time. Currently the comet is a morning object in Virgo, C/2018 V1 can be seen a degree to the east of the well known variable star Porrima (gamma Vir).

Congratulations to Don, Fujikawa-san and Iwamoto-san!

Below, a 60-second image of C/2018 V1 (Machholz-Fujikawa-Iwamoto) was taken by Martin Mobberley via iTelescope’s T14 FSQ106 telescope in New Mexico.

 
 

ALPO COMET NEWS FOR NOVEMBER 2018

2018-November-5

Comet 46P/Wirtanen rapidly brightens this month as it approaches to within 0.078 AU of the Earth on Dec 16. Depending on how dark your skies are, Wirtanen may be a naked eye object in December (or even as early as late November). Wirtanen isn’t the only cometary attraction this month. Two short-period comets come to perihelion in November. Both 38P/Stephan-Oterma and 64P/Swift-Gehrels should peak between magnitude 9 and 9.5 this month.

Bright Comets (magnitude < 10)

38P/Stephan-Oterma – Halley family comet 38P/Stephan-Oterma has an orbital period of ~38 years and is returning for the first time since 1980. This comet has a bit of an interesting backstory. In 1867, it was first sighted by Jérôme E. Coggia (Marseilles, France) who thought he had found an uncatalogued nebula. Over the following nights, followup observations by E. J. M. Stephan (Marseilles, France) uncovered the true nature of the object. For some reason, the discovery announcement cited Stephan as the discoverer with no mention of Coggia. After being missed at its next return in 1904, the comet was photographically rediscovered in 1942 by Liisi Oterma (Turku, Finland).

Stephen-Oterma is a morning object though it should be high enough to observe for most northern observers by 11 pm to midnight. This month should see the comet at its brightest (between magnitude 9.0 and 9.5) as it reaches perihelion (1.59 AU) on November 10 and closest approach to Earth (0.77 AU) on December 17. It will be moving through Gemini (Nov 1-25, 28-29) and Cancer (25-28, 29-30).

38P/Stephan-Oterma
T = 2018-Nov-10  q = 1.59 AU   Short-Period comet  Period = 38.0 yr
     Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-11-01   9.6   07 10  +18 37   1.593   0.935   111    Gem
2018-11-11   9.4   07 32  +21 30   1.588   0.872   116    Gem
2018-11-21   9.3   07 52  +24 50   1.593   0.823   122    Gem
2018-12-01   9.3   08 09  +28 34   1.608   0.788   129    Cnc

46P/Wirtanen – The brightest comet of the year will be 46P/Wirtanen which passes within 0.078 AU of the Earth in mid-December.
While the comet is still a southern object, this month sees the comet start its acceleration northward across the sky. Starting the month at a declination of -33 degrees, Wirtanen ends the month at -19 degrees as it moves through Fornax (Nov 1-27) and Cetus (27-30). Next month the comet will be located at significantly more northern declinations.

Chris Wyatt reported Wirtanen to be at magnitude 7.7 on November 3. This is very close to the prediction based on past apparitions. Its rapid brightening should bring the comet to magnitude 7.0 by the 10th, 6.0 by the 20th and 5.0 by the 28th. Recent CCD images by Martin Mobberley have even caught the development of a gas tail.

Assuming it behaves as in the past, Wirtanen should peak around magnitude 3 in mid-December. Note, that as a short-period comet, Wirtanen is likely to be a large diffuse object around the time of closest approach. It is possible its coma diameter will be in excess of 1 degree. Already visual observations by Chris Wyatt and CCD observations by Raymond Ramlow show Wirtanen to possess a coma with a diameter of 20+ arc minutes (0.33 degrees). Even at its brightest, do not expect the comet to appear as bright as a 3rd magnitude star since its light will be spread over a large area. Observers may need a relatively dark sky to see Wirtanen with the naked eye.

46P/Wirtanen
T = 2018-Dec-12  q = 1.06 AU   Short-Period comet  Period = 5.4 yr
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-11-01   8.0   01 59  -33 03   1.195   0.275   132    For
2018-11-11   6.9   02 02  -32 33   1.140   0.221   128    For
2018-11-21   5.8   02 11  -29 05   1.096   0.169   126    For
2018-12-01   4.6   02 32  -19 51   1.068   0.121   129    Cet

64P/Swift-Gehrels – Comet Swift-Gehrels was originally discovered visually by Lewis Swift (Rochester, New York) in 1889. Swift was also the discoverer of the Perseid parent body, Swift-Tuttle. After the 1889 apparition Swift’s comet went unobserverd until 1973 when its was rediscovered by Tom Gehrels on photographic plates taken at Palomar Observatory in southern California. 2018 marks Swift-Gehrels’ 7th observed return. Since its discovery in 1889, the comet’s orbit has been fairly stable with an orbital period of 9.4 years and perihelion distance near its current value of 1.39 AU. Not an especially bright object, this year’s return will be its best known return with a minimum Earth-comet distance of 0.44 AU on October 28. You will have to wait till 2092 for another return as good as this year’s though the 2046 return will be just a little worse than this year.

64P has already shown some excitement with a short lived outburst that saw it brighten by ~2-3 magnitudes to around 13th magnitude in mid-August. After its outburst, Swift-Gehrels seemed to be running a little brighter than expected. The most recent magnitude estimates from Chris Wyatt and Salvador Aguirre place the comet around magnitude 9.9-10.0 which is fairly close to its predicted brightness.

Now an evening object, Swift-Gehrels can be seen moving through Andromeda (Nov 1-25) and Triangulum (25-30). Perihelion occurs on November 3 at 1.39 AU and closest approach to Earth was a week earlier on October 27 at 0.44 AU. In the past, the comet reached its peak intrinsic brightness five weeks after perihelion. If it follows the same pattern, Swift-Gehrels should continue to brighten to a late November peak at magnitude 9.5.

64P/Swift-Gehrels
T = 2018-Nov-03  q = 1.39 AU   Short-Period comet  Period = 8.9 yr.
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-11-01  10.1   00 48  +36 53   1.394   0.446   148    And
2018-11-11   9.7   01 02  +36 45   1.396   0.457   146    Tri
2018-11-21   9.5   01 20  +35 54   1.408   0.481   144    Tri
2018-12-01   9.5   01 42  +34 34   1.431   0.519   141    Tri

Faint Comets (between magnitude 10 and 13)

21P/Giacobini-ZInner - Short-period comet 21P/Giacobini-Zinner is now two months past its September perihelion. After reaching a peak brightness of around magnitude 7.0, the comet faded more rapidly than expected in October. A CCD observation by Raymond Ramlow on November 4 found Giacobini-Zinner at magnitude 10.4.

November should see the comet steadily fade as it moves away from the Sun and Earth. The comet also continues moving deeper into the southern sky. Visual and CCD observers can continue to enjoy the comet moving against the rich Milky Way constellations of Canis Major (Nov 1-11) and Puppis (11-30).

Looking ahead, Giacobini-Zinner’s next return in 2025 will be very poor with the comet located on the other side of the Sun at perihelion. In 2031 the comet will be better placed with a minimum Earth-comet distance of 0.55 AU (versus 0.39 AU this year) and a slightly larger perihelion distance of 1.07 AU (versus 1.01 AU this year). The comet should brighten to magnitude 8 or so that year.

21P/Giacobini-Zinner
T = 2018-Sep-10  q = 1.01 AU   Short-Period comet  Period = 6.5 yr
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-11-01  10.4   07 25  -28 08   1.245   0.660    95    CMa
2018-11-11  11.2   07 24  -33 09   1.326   0.727    99    CMa
2018-11-21  11.9   07 17  -36 42   1.412   0.793   104    Pup
2018-12-01  12.5   07 07  -38 53   1.501   0.859   108    Pup

C/2016 M1 (PANSTARRS) – Comet C/2006 M1 (PANSTARRS) continues to slowly fade. Visual observations by Chris Wyatt on November 3 found the comet at magnitude 10.4. Having passed perihelion on August 10 at 2.21 AU and now moving away from both the Earth and Sun, C/2016 M1 should continue to slowly fade as it moves through the southern constellations of Circinus and Apus.

C/2016 M1 (PANSTARRS)
T = 2018-Aug-10  q = 2.21 AU   Long-Period comet - dynamically old
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-11-01  10.7   14 50  -68 16   2.406   2.848    54    Cir
2018-11-11  10.9   15 03  -70 56   2.453   2.906    53    Aps
2018-11-21  11.0   15 20  -73 52   2.504   2.950    54    Aps
2018-12-01  11.2   15 42  -77 04   2.558   2.982    55    Aps

C/2016 N6 (PANSTARRS) – Yet another faint, high q, PANSTARRS discovery, C/2016 N6 was imaged by Raymond Ramlow at magnitude 12.6 on November 2nd and observed visually by J. J. Gonzalez at magnitude 11.8 on October 20. The comet is now 4 months past perihelion (2.67 AU on July 18, 2018). A decreasing Earth-comet distance will result in the comet staying near magnitude 12 even though it is moving away from the Sun in November.

C/2016 N6 (PANSTARRS)
T = 2018-Jul-18 q = 2.67 AU   Long-Period comet - dynamically old
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-11-01  12.2   08 54  +02 17   2.889   2.836    83    Hya
2018-11-11  12.2   08 47  -01 09   2.930   2.699    93    Hya
2018-11-21  12.2   08 37  -04 44   2.974   2.575   104    Hya
2018-12-01  12.2   08 23  -08 28   3.020   2.473   114    Hya

Other Comets of Interest

(944) Hidalgo and (3552) Don Quixote – Two bright low activity or dormant comets come to perihelion this year. (3552) Don Quixote is still designated an asteroid even though a tail was seen in 2009 with the Spitzer IR space telescope and again this March at visible wavelengths with a 4.1-m telescope. This month Don Quixote is fading from magnitude 16.5 to 17.2. (944) Hidalgo reaches peak brightness at magnitude 14.3 this month. Unlike Don Quixote, Hidalgo has shown no cometary activity so far.

(944) Hidalgo
T = 2018-Oct-26  q = 1.95 AU   Extinct comet       Period = 13.8 yr
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-11-01  14.4   08 35  +70 59   1.948   1.476   102    UMa
2018-11-11  14.3   09 34  +73 38   1.954   1.456   104    Dra
2018-11-21  14.3   10 37  +75 27   1.964   1.448   105    Dra
2018-12-01  14.3   11 36  +76 34   1.979   1.450   107    Dra
(3552) Don Quixote
T = 2018-May-07  q = 1.24 AU   Extinct comet       Period =  8.8 yr
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-11-01  16.5   01 29  +54 13   2.393   1.556   138    Cas
2018-11-11  16.7   01 12  +53 05   2.475   1.647   138    Cas
2018-11-21  16.9   01 01  +51 31   2.557   1.759   135    Cas
2018-12-01  17.2   00 56  +49 49   2.638   1.891   130    Cas

As always, the Comet Section is happy to receive all comet observations, whether images, drawings, magnitude estimates, and even spectra. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.
- Carl Hergenrother (ALPO Comet Section Coordinator)

 
 

ALPO COMET NEWS FOR OCTOBER 2018

2018-OCTOBER-5

This month will up to four comets as bright or brighter than 10th magnitude. 21P/Giacobini-Zinner will fade from 7th to 9th magnitude as it rapidly moves south. As 21P fades, the next bright comet, 46P/Wirtanen, quickly brightens to take its place. In addition to 46P, comets 38P/Stephan-Oterma and 64P/Swift-Gehrels brighten to near or slightly brighter than magnitude 10.0.

Bright Comets (magnitude < 10)

21P/Giacobini-Zinner – Short-period comet 21P/Giacobini-Zinner starts the month as the brightest comet at magnitude ~7.7. Now a few weeks past perihelion and its closest approach to Earth, 21P will be fading this month and should hand its ‘brightest comet’ title to 46P/Wirtanen towards the end of the month.

G-Z has provided observers with a number of memorable views as it traveled through the star, cluster and nebula-rich winter Milky Way. October will be no different as it moves southwards through Monoceros (Oct 1-9) and Canis Major (9-31). Close approaches to the following deep sky objects occur this month: open clusters NGC 2311 (Oct 3), M50 (Oct 6/7), NGC 2335 (Oct 8), Cr 465 (Oct 8/9), NGC 2343 (Oct 8/9), NGC 2345 (Oct 11), NGC 2360 (Oct 14). CCD images have shown a nice long dust tail. Observers are encouraged to watch the evolution of 21P’s dust tail as we pass through orbit plane crossing on October 9th.

Visual observations submitted to the ALPO over the last week or so show 21P to be between magnitude 7.4 and 7.6. This suggests the comet is running a little fainter than expected. Then again the Moon had been bright and/or nearby and possibly hid the outer extent of 21P’s coma resulting in fainter estimates.

21P/Giacobini-Zinner
T = 2018-Sep-10  q = 1.01 AU   Short-Period comet  Period = 6.5 yr
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-10-01   7.6   06 51  +00 03   1.055   0.453    84    Mon
2018-10-11   8.2   07 08  -11 42   1.103   0.515    87    CMa
2018-10-21   8.8   07 19  -20 41   1.165   0.583    91    CMa
2018-10-31   9.5   07 24  -27 33   1.237   0.653    95    CMa

38P/Stephan-Oterma – Comet Stephan-Oterma has an orbital period of ~38 years and is returning for the first time since 1980. This comet has a bit of an interesting backstory. In 1867, it was first sighted by Jérôme E. Coggia (Marseilles, France) who thought he had found an uncatalogued nebula. Over the following nights, followup observations by E. J. M. Stephan (Marseilles, France) uncovered the true nature of the object. For some reason, the discovery announcement cited Stephan as the discoverer with no mention of Coggia. After being missed at its next return in 1904, the comet was photographically rediscovered in 1942 by Liisi Oterma (Turku, Finland).

This month, 38P will be a morning object in Orion and Gemini as it brightens from 11th to just brighter than 10th magnitude. Ultimately the comet will peak around magnitude 9.0 to 9.5 in late November after its perihelion on November 10 at 1.59 AU. In 1980, Stephan-Oterma approached to within 0.59 AU of Earth and brightened to between magnitude 8.5 and 9.0. This year’s return will be a little further away at 0.76 AU, hence the slightly fainter maximum brightness.

38P/Stephan-Oterma
T = 2018-Nov-10  q = 1.59 AU   Short-Period comet  Period = 38.0 yr
Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-10-01  10.8   05 55  +11 56   1.670   1.199    98    Ori
2018-10-11  10.4   06 20  +13 47   1.636   1.102   102    Ori
2018-10-21  10.0   06 44  +15 54   1.610   1.016   106    Gem
2018-10-31   9.7   07 08  +18 21   1.594   0.941   111    Gem

46P/Wirtanen – The brightest comet of the year should be 46P/Wirtanen which will pass within 0.08 AU of the Earth in mid-December. Wirtanen will be located around a southern declination of -30 degrees till late November (in the constellations of Cetus and Fornax). The comet will rapidly brighten from 11th to 8th magnitude this month. The comet will become better placed for northern observers starting in late November as it rapidly moves north. Assuming it behaves as it has in the past, Wirtanen should peak around magnitude 3 in mid-December. Note, that as a short-period comet, Wirtanen is likely to be a large diffuse object around the time of closest approach. It is possible its coma diameter will be in excess of 1 degree. Do not expect it to appear as bright as a 3rd magnitude star since it light will be spread over a large area. Observers may need a relatively dark sky to see Wirtanen with the naked eye.

46P/Wirtanen
T = 2018-Dec-12  q = 1.06 AU   Short-Period comet  Period = 5.4 yr
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-10-01  11.3   01 53  -26 14   1.418   0.479   144    For
2018-10-11  10.3   01 56  -29 09   1.340   0.404   141    For
2018-10-21   9.2   01 57  -31 35   1.267   0.339   137    For
2018-10-31   8.1   01 59  -32 59   1.201   0.280   132    For

Faint Comets (between magnitude 10 and 13)

64P/Swift-Gehrels – Comet Swift-Gehrels was originally discovered visually by Lewis Swift (Rochester, New York) in 1889. Swift was also the discoverer of the Perseid parent body, Swift-Tuttle. After the 1889 apparition Swift’s comet went unobserverd until 1973 when its was rediscovered by Tom Gehrels on photographic plates taken at Palomar Observatory in southern California. 2018 marks Swift-Gehrels’ 7th observed return. Since its discovery in 1889, the comet’s orbit has been fairly stable with an orbital period of 9.4 years and perihelion distance near its current value of 1.39 AU. Not an especially bright object, this year’s return will be its best known return with a minimum Earth-comet distance of 0.44 AU on October 28. You will have to wait till 2092 for another return as good as this year’s though the 2046 return will just a little worse.

64P has already shown some excitement with a short lived outburst that saw it brighten by ~2-3 magnitudes to around 13th magnitude in mid-August. Swift-Gehrels has since settled down again and, unless it outbursts again, should brighten from 15th to 12th magnitude this month. Peak brightness will be around magnitude 9.5 in late November.

The magnitudes given below are based on 64P’s behavior during its 1981 apparition. Even considering its mid-August outburst, 64P seems to be running brighter than predicted. Observations submitted to COBS over the past few days show the comet to be between magnitude 10.1 and 11.4.

64P/Swift-Gehrels
T = 2018-Nov-03  q = 1.39 AU   Short-Period comet  Period = 8.9 yr
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-10-01  12.2   00 28  +31 27   1.452   0.491   151    And
2018-10-11  11.4   00 32  +34 10   1.423   0.463   151    And
2018-10-21  10.7   00 37  +35 59   1.403   0.448   150    And
2018-10-31  10.1   00 46  +36 51   1.394   0.445   149    And

C/2016 M1 (PANSTARRS) – Visual observations by Chris Wyatt on October 1 found the comet at magnitude 10.2. Having passed perihelion on August 10 at 2.21 AU and now moving away from both the Earth and Sun, C/2016 M1 should continue to slowly fade as it moves through the southern constellations of Centaurus and Circinus.

C/2016 M1 (PANSTARRS)
T = 2018-Aug-10  q = 2.21 AU   Long-Period comet - dynamically old
Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-10-01  10.1   14 27  -61 51   2.290   2.564    62    Cen
2018-10-11  10.3   14 32  -63 37   2.322   2.673    58    Cen
2018-10-21  10.5   14 39  -65 40   2.360   2.766    56    Cir
2018-10-31  10.7   14 49  -68 01   2.402   2.842    54    Cir

C/2016 R2 (PANSTARRS) - CO+ rich comet C/2016 R2 (PANSTARRS) continues its very slow fade. Thanks to its large perihelion distance (2.60 AU), the comet experiences slow changes in its heliocentric and geocentric distances. The comet should remain around 12th magnitude this month as it pulls away from the Sun in the northern morning sky.

C/2016 R2 (PANSTARRS)
T = 2018-May-02  q = 2.60 AU   Long-Period comet - dynamically old
 Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-09-01  11.7   10 58  +50 43   2.869   3.532    42M   UMa
2018-09-11  11.8   11 27  +49 40   2.914   3.538    44M   UMa
2018-09-21  11.9   11 56  +48 29   2.962   3.544    47M   UMa
2018-10-01  12.0   12 23  +47 14   3.012   3.552    50M   CVn

Other Comets of Interest

(944) Hidalgo and (3552) Don Quixote – Two bright low activity or dormant comets come to perihelion this year. (3552) Don Quixote is still designated an asteroid even though a tail was seen in 2009 with the Spitzer IR space telescope and again this March at visible wavelengths with a 4.1-m telescope. This month Don Quixote is near magnitude 16.3. (944) Hidalgo is still inbound and will peak in brightness at 14.3 in November. Unlike Don Quixote, Hidalgo has shown no cometary activity so far.

364P/PANSTARRS – 364P/PANSTARRS is a low activity comet that only shows activity at small heliocentric distances. Discovered in 2013, 364P is making its second observed return with perihelion having occurred in late June at 0.80 AU. Cometary activity has now ceased though a residual dust tail is still visible. This month CCD observers will be able to image the bare nucleus of 364P as it fades from magnitude 17.7 to 19.3.

364P/PANSTARRS
T = 2018-Jun-24  q = 0.80 AU   Short-Period comet  Period =  4.9 yr
Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-10-01  17.6   00 02  -23 18   1.625   0.668   153    Cet
2018-10-11  18.1   23 49  -20 18   1.728   0.801   147    Aqr
2018-10-21  18.7   23 42  -17 32   1.828   0.953   139    Aqr
2018-10-31  19.3   23 40  -15 01   1.927   1.122   131    Aqr
(944) Hidalgo
T = 2018-Oct-26  q = 1.95 AU   Extinct comet       Period = 13.8 yr
Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-10-01  14.6   06 18  +58 31   1.964   1.625    93    Lyn
2018-10-11  14.5   06 55  +63 01   1.954   1.561    97    Cam
2018-10-21  14.4   07 38  +67 09   1.948   1.512    99    Cam
2018-10-31  14.4   08 30  +70 40   1.948   1.478   102    UMa
(3552) Don Quixote
T = 2018-May-07  q = 1.24 AU   Extinct comet       Period =  8.8 yr
Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-10-01  16.3   02 34  +52 15   2.134   1.405   124    Per
2018-10-11  16.3   02 14  +53 58   2.218   1.433   130    Per
2018-10-21  16.4   01 52  +54 37   2.301   1.480   135    Per
2018-10-31  16.5   01 31  +54 18   2.384   1.548   138    Per

As always, the Comet Section is happy to receive all comet observations, whether images, drawings, magnitude estimates, and even spectra. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.
- Carl Hergenrother (ALPO Comet Section Coordinator)

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