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ALPO Comet News for December 2018

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#1 Carl H.

Carl H.

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Posted 06 December 2018 - 12:21 PM

ALPO COMET NEWS FOR DECEMBER 2018
 
2018-December-6
 
The highlight of the month is 46P/Wirtanen’s close approach to Earth. Wirtanen will be the brightest non-outbursting Jupiter-family comet in many decades. In addition to Wirtanen, 38P/Stephan-Oterma and 64P/Swift-Gehrels continue brighter than magnitude 10. In addition to the bright three, this report contains news of other slightly fainte, but no less interesting, objects.

 

Bright Comets (magnitude < 10)
  
46P/Wirtanen - The comet event of 2018 is this month’s close approach of comet 46P/Wirtanen to the Earth. For months there have been predictions that Wirtanen will brighten to a naked eye object. Now only a week or so till closest approach on December 16 at 0.078 AU and perihelion on December 12 at 1.055 AU, the comet appears to be as bright as predicted. While this is good news for it reaching its predicted peak between magnitude 3.0 and 3.5, how bright it will appear to you will be dependent on your equipment and sky darkness. Currently the comet is around magnitude 4.5 but it does not appear as bright as a magnitude 4.5 star. Instead its light is spread over a sizable coma. Recent observations have estimated a coma with a diameter anywhere from 20’ to 110’ across. The comet should appear to grow even larger as it approaches closer. While no visual observers have reported seeing a tail, CCD images have detected a long but faint and narrow ion tail displaying rapid changes in morphology.

 

After spending the last few months at southern declinations, 46P is now racing northwards and will transition to a far northern object by the end of December. This month 46P will be traversing Cetus (Dec 1-4), Eridanus (4-9), Cetus (9-11), Taurus (11-18), Perseus (18-19), Auriga (19), Perseus (19-20), Auriga (20-27) and Lynx (27-31). Heading into 2019, it will be fading but may should still be as bright as magnitude 4.0.

 

While comets that brighten to magnitude 3.0 to 3.5 happen every few years, they are usually long-period comets (most recently C/2011 L4 PANSTARRS in 2013). It is rare to see just a bright Jupiter-family comet. 17P/Holmes was brighter during its 2007 outburst. For non-outbursting Jupiter-family comets, 96P/Machholz routinely peaks at around 2nd magnitude. But do to its small solar elongation at perihelion, that brightness is never experienced by Earth-based observers. We may need to go back to 1927 when 6P/Pons-Winnecke passed within 0.04 AU of Earth and brightened to magnitude 3.5.

The ALPO has received 47 images of 46P/Wirtanen this apparition. We are always looking for observers to contribute their observations (whether visual magnitude estimates, sketches, photos, images, spectra, or just textual descriptions).

 

To see what the ALPO has received for 46P, please check our Comet Section Image Gallery at
http://www.alpo-astr...0P/46P-Wirtanen

 

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
2018-12-01   4.6   02 32  -19 51   1.068   0.121   129    Cet
2018-12-11   3.5   03 16  +02 18   1.056   0.085   145    Tau
2018-12-21   3.2   04 44  +37 38   1.061   0.082   159    Aur
2018-12-31   4.0   06 49  +56 35   1.083   0.117   146    Lyn
2019-01-10   5.0   08 20  +59 35   1.121   0.170   141    Lyn

 

38P/Stephan-Oterma - Halley-family comet 38P/Stephan-Oterma has an orbital period of ~38 years and is making its first return since 1980. Stephen-Oterma is a morning object though it should be high enough to observe for most northern observers by late evening. The comet should be starting to fade now since it is passed perihelion (1.59 AU on November 10) though still approaching its closest to Earth (0.77 AU) on December 17. It will be moving through Cancer (Dec 1-11) and Lynx (11-31).

 

Magnitude estimates during November have been a little scattered for this object with a range between magnitude 9 and 11. Though the comet should have continued to brighten through the end of November, observations from the end of the month hint at the start of a fading trend. If so, the predicted magnitudes given below may be optimistic by half a magnitude or more.
 
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
2018-12-01   9.3   08 09  +28 34   1.608   0.788   129    Cnc 
2018-12-11   9.4   08 22  +32 36   1.633   0.769   136    Cnc
2018-12-21   9.6   08 31  +36 40   1.666   0.767   143    Lyn
2018-12-31   9.9   08 35  +40 26   1.708   0.784   150    Lyn
2019-01-10  10.3   08 35  +43 34   1.757   0.820   153    Lyn

    
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. Recent magnitude estimates show some scatter but show signs of a comet that is running brighter than expected. Since the start of December, visual magnitude reports to COBS span between magnitude 8.1 and 10.5 with most reports around magnitude 9.0. We are now well passed perihelion (November 3 at 1.39 AU) and closest approach to Earth (October 27 at 0.44 AU). Its continued brightening after perihelion was predicted based on past performance or at least how it performed at its well observed apparition in 1981.

 

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
2018-12-01   9.2   01 42  +34 34   1.431   0.519   141    Tri
2018-12-11   9.3   02 06  +33 01   1.463   0.572   138    Tri
2018-12-21   9.7   02 30  +31 27   1.503   0.640   134    Tri
2018-12-31  10.1   02 55  +30 02   1.551   0.724   129    Ari
2019-01-10  10.8   03 19  +28 48   1.605   0.823   125    Ari

  
Faint Comets (between magnitude 10 and 13)
   
C/2016 M1 (PANSTARRS) - Comet C/2006 M1 (PANSTARRS) just keeps on going and going. Now well passed it rather distant (2.21 AU) August 10th perihelion, this dynamically old long-period comet has been slow to fade. Chris Wyatt has bee continuously monitoring it and throughout November he found it to be between magnitude 10.4 and 10.8. C/2016 M1 is located deep in the southern sky an will be close to the southern celestial pole this month as it moves through Apus and Octans.
 
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
2018-12-01  11.2   15 42  -77 04   2.558   2.982    55    Aps   
2018-12-11  11.4   16 17  -80 27   2.616   3.004    57    Aps      
2018-12-21  11.6   17 26  -83 50   2.676   3.021    60    Oct   
2018-12-31  11.8   20 25  -86 08   2.740   3.034    63    Oct   
2019-01-10  12.0   00 14  -84 38   2.805   3.049    66    Oct    

 

C/2018 L2 (ATLAS) - A nice surprise comet, C/2018 L2 was discovered during the course of the ATLAS, or "Asteroid Terrestrial-impact Last Alert System", survey on June 6th with a 0.5-m f/2 Schmidt reflector at Mauna Loa, Hawaii. At the time of discovery the comet was 15th magnitude. As recently as September 6th, the comet was around magnitude 14. On October 3rd, J. J. Gonzalez reported the comet visually at magnitude 9.8. Other observations placed the comet between magnitude 9.1 and 11.7 over the past month. Comet ATLAS is a dynamically old long-period comet. Such comets can brighten rapidly as they approach perihelion. They are also prone to possessing large gas coma. While the comet's recent increase in brightness may be due to an outburst, it is possible that observers have started to detect a large, low surface brightness, gas coma that was not detected earlier. 
 
Comet ATLAS passed perihelion on 2018 December 2 at a distance of 1.71 AU from the Sun. The magnitude predictions below are uncertain due to the large reported scatter.
 
C/2018 L2 (ATLAS)


T = 2018-Dec-02  q = 1.71 AU

   Long-Period comet - dynamically old
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-12-01  10.2   17 29  +09 03   1.712   2.433    34    Oph     
2018-12-11  10.2   17 55  +11 56   1.715   2.403    36    Oph    
2018-12-21  10.3   18 22  +15 04   1.729   2.377    39    Her    
2018-12-31  10.4   18 52  +18 25   1.752   2.360    41    Her    
2019-01-10  10.7   19 23  +21 54   1.784   2.356    43    Vul    

 
C/2018 V1 (Machholz-Fujikawa-Iwamoto - This new comet was discovered by renowned amateur comet hunters Don Machholz, Shigehisa Fujikawa and Masayuki Iwamoto on November 7. This marked 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)]. 
  
This 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). Don Machholz's previous 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), C/2004 Q2 (Machholz) and C/2010 F4 (Machholz).

The comet was only well placed for observation for a few weeks. In November it appeared to rapidly brighten from around magnitude 10 at discovery to between 7.5 and 8.0 a few days later. Now located in the evening sky, a few successful attempts have been made to observe the comet even at an elongation around 20 degrees. The only magnitude estimate I could find was by Timo Karhula on COBS on Dec 5 at magnitude 9.4. The comet will not be an easy object to observe this month as it never get far from the Sun and by mid-month is falling back into the Sun’s glare. The comet won’t be visible from the ground again till February when it should be much fainter.

 

C/2018 V1 (Machholz-Fujikawa-Iwamoto)
T = 2018-Dec-03  q = 0.39 AU   Long-Period comet


    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-12-01   7.2   16 57  -04 11   0.393   0.706    19    Oph 
2018-12-11   8.5   18 43  -11 54   0.438   1.043    24    Sct
2018-12-21  10.6   19 18  -17 46   0.602   1.417    20    Sgr
2018-12-31  12.2   19 35  -21 42   0.795   1.721    13    Sgr 
2019-01-10  13.4   19 47  -24 32   0.989   1.961     6    Sgr 

 

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 17.2 to 18.2. (944) Hidalgo is still near its peak brightness this month. Unlike Don Quixote, Hidalgo has shown no cometary activity so far. Both comets are located at northern declinations.
 
(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
2018-12-01  14.3   11 36  +76 34   1.979   1.450   107    Dra       
2018-12-11  14.3   12 26  +77 17   2.000   1.458   108    Cam       
2018-12-21  14.4   13 03  +77 57   2.024   1.472   109    Cam    
2018-12-31  14.4   13 25  +78 44   2.053   1.492   110    Cam    
2019-01-10  14.5   13 30  +79 43   2.087   1.517   111    Cam      

 
(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
2018-12-01  17.2   00 56  +49 49   2.638   1.891   130    Cas      
2018-12-11  17.4   00 55  +48 12   2.718   2.040   124    Cas       
2018-12-21  17.7   00 57  +46 46   2.797   2.204   117    Cas    
2018-12-31  17.9   01 03  +45 36   2.875   2.380   110    And     
2019-01-10  18.2   01 11  +44 42   2.952   2.565   103    And    

 
New Discoveries

 

C/2018 W2 (Africano) - This comet was discovered nearly simultaneously by H. Groeller with the Catalina Sky Survey 0.68-m schmidt and Brian Africano with the Mount Lemmon 1.5-m reflector. Groeller actually observed the comet first but Africano was the first to submit his discovery report to the MPC. C/2018 W2 is a long-period comet that will reach perihelion on 2019 September 15 at 1.59 AU. It may peak as bright as magnitude 10-11 next September/October when it will approach to within 0.68 AU of Earth.

 

A/2018 W1 - Greg Leonard discovered this object on November 2 at 19th magnitude with the Catalina Sky Survey 0.68-m schmidt. It is a Halley-family object with a 100 year period and perihelion on 2019 May 11 at 1.36 AU. Unless it becomes active, A/2018 W1 should not become much brighter than its current 19th magnitude.

 

C/2018 V4 (Africano) - C/2018 V4 was also found by Africano with the Mount Lemmon 1.5-m. At discovery on November 4, it was 19th magnitude. It is a dynamically old long-period comet with a perihelion on 2019 March 1 at 3.20 AU. It is not expected to get brighter than 19th magnitude.

 

A/2018 V3 - This object was discovered with the Pan-STARRS2 telescope on November 2 at magnitude 21. Currently showing no cometary activity, this object reaches perihelion on 2019 September 8 at 1.34 AU and closest approach to Earth on 2019 August 19 at 0.38 AU. Even if it stays inactive, it will reach 15th magnitude in mid-August. Its orbit is of the dynamically old long-period type so there is a good chance this object is only currently inactive due to its large heliocentric distance of 3.76 AU. It may very well become an active comet as it gets closer and could become much brighter than 15th magnitude.

 

C/2018 V2 (ATLAS) - The ATLAS survey found this comet on November 2 at 19th magnitude. The comet is as bright as it will get. It is a Halley-type comet with an orbital period of 130 years and perihelion on 2018 November 26 at 2.45 AU.

 

P/2018 VN2 (Leonard) - Greg Leonard also found this comet with the Mount Lemmon 1.5-m. At discovery on November 5, it was 19th magnitude. It will not be getting any brighter this return. The comet is on a 8.1 year period orbit and reached perihelion back on 2018 June 7 at 2.11 AU.

 

C/2018 U1 (Lemmon) - Rich Kowalski found this comet on October 27th at 20th magnitude with the Mount Lemmon 1.5-m. It may peak at around magnitude 15 near its 2021 November 1 perihelion at 4.98 AU.

 

P/2017 TW13 (Lemmon) - Jess Johnson found P/2017 TW13 back on 2017 September 1 at 20th magnitude with the Mount Lemmon 1.5-m. At that time the object did not show cometary activity. H. Sato noted a coma on images taken on 2018 October 13 with a 0.6-m astrograph. P/2017 TW13 is a short-period comet on a 19.2 year orbit with perihelion on 2018 June 20 at 2.08 AU.

 

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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