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ALPO Comet News for June 2018

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#1 Carl H.

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Posted 01 June 2018 - 06:47 PM

ALPO COMET NEWS FOR JUNE 2018

 

2018-June-1

 

Hello Comet Observers!

 

After a few months of no bright comets, May brought a 9th magnitude comet in C/2016 M1 (PANSTARRS). This comet should continue to be the brightest this month though C/2017 T3 (ATLAS) may challenge it.

 

Bright Comets (magnitude < 10)

 

C/2016 M1 (PANSTARRS) - This dynamically old long-period comet was well observed in May with observers reporting it between magnitude 8.5 and 9.6 during the past week. It should continue to brighten by another 0.5 magnitudes this month as it approaches an August 10 perihelion at 2.21 AU. Increasing distance from the Earth after closest approach on June 24 at 1.29 AU will cause a slow fade beginning in late June.

 

Visual observations found the comet to have a fairly condensed coma (DC between 3 and 5) with a diameter between 3'and 5'. No visual reports of a tail have been made though the coma was observed to be slightly elongated.

 

The comet's 91 degree inclination orbit is resulting in a steady southward motion from a June 1 declination of -24 degrees to -46 at the end of the month. It will be seen moving among the stars of Sagittarius, Corona Australis and Ara. A few close approaches to deep space objects will occur this month (Jun 9 - globular cluster M54 and Jun 12/13 - globular cluster M70).

 

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

2018-06-01   9.2   19 15  -24 24   2.353   1.463   142M   Sgr
2018-06-11   8.9   18 53  -31 41   2.317   1.349   156M   Sgr
2018-06-21   8.8   18 21  -39 26   2.285   1.293   163M   CrA
2018-07-01   8.7   17 39  -46 24   2.259   1.301   153E   Ara

 

C/2017 T3 (ATLAS) - It is questionable whether or not this comet will be observable and, if so, how bright it will be this month. C/2017 T3 (ATLAS) was discovered by the Hawai'i-based ATLAS (Asteroid Terrestrial-impact Last Alert System) project on October 14, 2017 at 18th magnitude. At the time the comet was located 4.0 AU from the Sun.

 

A dynamically-old short-period comet, ATLAS was brightening at a slightly faster than expected rate (2.5n ~ 11 compared to 2.5n ~ 10 which is usually, and often incorrectly, assumed for all long-period comets). This month, southern hemisphere observers may be able to reacquire the comet as it slowly moves away from the Sun in the morning sky. Since the comet has been out of view since April, its currently brightness is uncertain. Assuming (and we know the old saying about making assumptions) the comet has continued to brighten at its pre-April rate, the comet may be as bright as magnitude 9.4 by the end of the month. 

 

Perihelion occurs on July 19 at 0.83 AU though the comet will be a rather distant 1.4 AU from the Earth at that time. With the same caveat about the assumption made above, the comet may peak around magnitude 8.6 around the time of perihelion. For southern hemisphere observers, the comet will be visible at a low elevations (~10 - 15 degrees in July). Unfortunately, it will be unobservable for northern hemisphere observers till the very end of the year when it will be a faint object (~16th magnitude).

 

C/2017 T3 (ATLAS)                                      

T = 2018-Jul-19  q = 0.83 AU   Long-Period comet - dynamically old

    Date     Mag    R.A.   Decl.     r       d    Elong  const

2018-06-01  11.4   03 47  +20 43   1.204   2.184    10M   Tau
2018-06-11  10.7   04 14  +16 40   1.084   2.026    15M   Tau
2018-06-21  10.0   04 44  +11 39   0.978   1.857    20M   Ori
2018-07-01   9.4   05 18  +05 24   0.893   1.685    26M   Ori

 

Faint Comets (between magnitude 10 and 13)

 

21P/Giacobini-ZInner - Many long-time observers may remember this comet’s last excellent return in the fall of 1985 just as Comet Halley was approaching its February 1986 perihelion. This year marks G-Z’s 16th observed return since its visual discovery in 1900 by Michel Giacobini (Nice, France). The comet was visually re-discovered 2 returns later in 1913 by Ernst Zinner (Bamberg, Germany), hence the double appellation. Perihelion and closest approach to Earth both occur on September 10 at 1.01 AU and 0.39 AU, respectively. This will be the comet’s closest approach to Earth since 1959 when it passed 0.35 AU from Earth.

 

Recent observations place 21P between magnitude 13.8 and 15.1 over the last week of May. This month the comet is high in the morning sky (for northern observers) as it moves through Cygnus. It should rapidly brighten from around magnitude 13 to 11 over the course of the month. A peak brightness of around magnitude 7 is predicted for early September. Though the comet will be located at high northern declinations over the next few months, it will travel far enough south for most southern hemisphere observers by mid-September.

 

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

2018-06-01  13.2   20 29  +33 15   1.682   1.157   101M   Cyg
2018-06-11  12.5   20 46  +38 43   1.590   1.045   100M   Cyg
2018-06-21  11.8   21 05  +44 23   1.498   0.943    99M   Cyg
2018-07-01  11.1   21 28  +50 08   1.409   0.849    97M   Cyg

 

48P/Johnson - 48P/Johnson has a large perihelion distance for a relatively bright short-period comet. Perihelion (2.00 AU) and closest approach to Earth (1.01 AU) occur within a week of each other in mid-August making this as good a return as possible for 48P. The comet should brighten from around magnitude 13 to 12 this month as it moves among the stars of Capricornus in the morning sky. This year marks its 11th observed return since it was discovered in 1949 by Ernest L. Johnson on photographs taken at the Union Observatory in Johannesburg, South Africa.

 

The brightest report from May was by the Catalina Sky Survey which placed Johnson at magnitude 14.8 on May 21. This is about 1.5 magnitudes fainter than the predicted magnitude. If the comet continues to run fainter than predicted, the magnitudes below may be too bright. 

 

48P/Johnson                                            
T = 2018-Aug-12  q = 2.00 AU   Short-Period comet  Period = 6.5 yr

    Date     Mag    R.A.   Decl.     r       d    Elong  const

2018-06-01  12.9   21 53  -14 58   2.084   1.580   104M   Cap
2018-06-11  12.6   22 07  -15 08   2.064   1.465   111M   Aqr
2018-06-21  12.2   22 19  -15 36   2.047   1.359   118M   Aqr
2018-07-01  11.9   22 28  -16 26   2.032   1.263   125M   Aqr

 

66P/du Toit - Short-period comet 66P/du Toit is still running brighter than predicted. Observers have been estimating it to be between magnitude 10.2 and 10.7 during the last week of May. The comet possesses a large, low surface brightness coma so the comet may appear fainter than expected to some observers. The comet remains a very difficult object for northern hemisphere observers. Personally, I have not been able to acquire it in my 30x125 binoculars due to a combination of its low elevation and a brightening dawn sky. This marks 66P's 4th observed and best apparition since its discovery by South African astronomer Daniel du Toit in 1944. The next return won't be till 2033 though with a minimum comet-Earth distance of 1.36 AU it should be a fainter object at that return.

 

66P/du Toit                                           
T = 2018-May-19  q = 1.29 AU   Short-Period comet  Period = 14.9 yr

    Date     Mag    R.A.   Decl.     r       d    Elong  const

2018-06-01  10.7   23 54  -30 48   1.302   0.903    85M   Scl 
2018-06-11  11.1   00 23  -27 41   1.326   0.911    86M   Scl 
2018-06-21  11.7   00 46  -24 49   1.363   0.918    89M   Scl 
2018-07-01  12.4   01 03  -22 15   1.410   0.923    93M   Cet

 

364P/PANSTARRS - 364P/PANSTARRS is an example of a low activity comet. Similar to other comets of this type (such as 169P/NEAT, 249P/LINEAR and 300P/Catalina), 364P is only active at small heliocentric distances. Whether this is due to age, evolution or the possibility that these objects originated in the asteroid Main Belt rather than the Kuiper Belt, is still TBD.

 

Discovered in 2013 as P/2013 CU129, it is making its second observed return. This comet has a rather short period (4.9 years) and is only active for a few months around perihelion. Perihelion occurs this month on the 24th at 0.80 AU from the Sun. The comet displayed a thin tail in May though it didn't possess much of a coma. CCD and large aperture visual observers can watch the comet approach and pass through perihelion this month. Northern observers will lose sight of the comet mid-month (regaining the comet in early September) while southern observers will have an uninterrupted view of the comet (though it will get very low in early July).

 

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

2018-06-01  13.7   08 55  +20 08   0.883   0.530    60E   Cnc
2018-06-11  12.5   08 56  +13 55   0.827   0.447    52E   Cnc
2018-06-21  11.5   08 47  +05 45   0.800   0.362    44E   Hya
2018-07-01  10.9   08 18  -04 58   0.805   0.290    37E   Hya

 

C/2016 N6 (PANSTARRS) and C/2016 R2 (PANSTARRS) - In addition to C/2016 M1, there are two other PANSTARRS long-period comets with relatively large perihelion distances visible this month. Both are early evening objects located north of the ecliptic. C/2016 R2 passed perihelion on May 2 at 2.60 AU. It is approaching solar conjunction this month though its location north of the ecliptic means it should remain observable though at low elevations through conjunction. C/2016 N6 reaches perihelion on July 18 at 2.67 AU. The comet will be become a more difficult object to observe as the month progresses and should be lost to most observers towards the end of the month. C/2016 R2 will spend the month around magnitude 11 while C/2016 N6 will be around magnitude 12.

 

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

2018-06-01  11.1   06 22  +48 36   2.613   3.389    34E   Aur
2018-06-11  11.1   06 47  +49 55   2.625   3.426    32E   Lyn 
2018-06-21  11.2   07 15  +51 00   2.641   3.455    31E   Lyn 
2018-07-01  11.2   07 44  +51 51   2.661   3.476    31E   Lyn

 

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

2018-06-01  12.0   07 56  +46 08   2.715   3.297    47E   Lyn 
2018-06-11  12.1   08 02  +42 39   2.698   3.401    39E   Lyn 
2018-06-21  12.1   08 08  +39 25   2.684   3.491    32E   Lyn 
2018-07-01  12.1   08 15  +36 23   2.675   3.565    24E   Lyn

 

Other Comets of Interest

 

Low activity comet (3552) Don Quixote is still designated an asteroid even though Spitzer Space Telescope observations from 2009 showed a faint coma and tail. This month Don Quixote is near its 2018 peak at around 16th magnitude. The object is steadily moving north in the morning sky and is now observable by observers at northern mid-latitudes.

 

(3552) Don Quixote
T = 2018-May-07  q = 1.24 AU   Short-Period comet  Period =  8.8 yr
    Date     Mag    R.A.   Decl.     r       d    Elong  const
2018-06-01  15.9   01 04  -02 58   1.280   1.511    56M   Cet
2018-06-11  15.9   01 25  +02 48   1.317   1.507    59M   Psc
2018-06-21  16.0   01 44  +08 22   1.365   1.501    62M   Psc
2018-07-01  16.0   02 01  +13 44   1.422   1.493    65M   Ari

 

Looking ahead, the later months of 2018 will see a few other comets reaching magnitude 10 or brighter. 38P/Stephan-Oterma was observed back in the summer of 2017 by Pan-STARRS at 21st magnitude. CCD observers have recently observed it at 17th magnitude now that it is coming out of solar conjunction. 64P/Swift-Gehrels was detected for the first time this apparition by Spacewatch on May 25 UT at magnitude 20.7. What should be this year's brightest comet, 46P/Wirtanen, was picked up by the Discovery Channel Telescope on May 8 UT at magnitude 20.3.

 

Dynamically new and intrinsically faint C/2017 S3 (PANSTARRS) has shown a very slow intrinsic brightening since its September 2017 discovery (2.5n ~ 5.5!). Perihelion occurs on August 15 at a small distance of 0.21 AU. Though the comet will be located too close to the Sun at that time, there is hope it could become bright (7th-8th magnitude) before becoming lost in the glare of the Sun. In mid-May the comet brightened to 15-16th magnitude. Extrapolating it's slow brightening trend suggests the comet will not be a bright visual object prior to becoming lost in the bright twilight sky. Then again the comet may brighten at a faster rate, especially if gas-rich, as it gets closer to the Sun. A major question remains as to whether it will be a bright visual object prior to perihelion. Being intrinsically faint and dynamically new there is also a real possibility that this comet's nucleus is small and will disintegrate at it nears the Sun.

 

C/2017 S3 (PANSTARRS)                                   
T = 2018-Aug-15  q = 0.21 AU   Long-Period comet - dynamically new
    Date     Mag    R.A.   Decl.     r       d    Elong  const

2018-06-01  15.7   01 09  +57 25   1.788   2.242    51M   Cas
2018-06-11  15.3   01 40  +58 23   1.614   2.030    51M   Cas
2018-06-21  14.7   02 16  +59 09   1.430   1.803    52M   Cas
2018-07-01  14.1   03 01  +59 24   1.237   1.562    52M   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)


Edited by Carl H., 02 June 2018 - 12:34 PM.

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#2 SpaceConqueror3

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Posted 01 June 2018 - 09:50 PM

Awesome. Thanks for these postings!



#3 Vickx

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Posted 02 June 2018 - 02:40 AM

Thank you very much!

Just please correct the typo: C/2017 T3 (ATLAS), not T1.

Vic



#4 Vickx

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Posted 04 June 2018 - 09:48 AM

I was able to spot 21P/Giacobini-Zinner finally last night (Jun 03.9 UT). Although still in the dense field of Milky Way in Cygnus it was relatively easy to see it using averted vision in a 16" under summer bright skies (SQM-L 21.0 MSA). The comet is small with almost stelar pseudonucleus. The best magnification was 288×.

Vic



#5 Raymond Ramlow

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Posted 04 June 2018 - 11:59 PM

Here's an image taken an hour ago (June 05.17) of 364P with iTelescope T20. The comet now has a faint outer coma, is magnitude 13.2, and has a tail of >4 arcminutes.

 

V, 300s, 24x36'

 

364_P_6-4-18.jpg


Edited by Raymond Ramlow, 05 June 2018 - 12:00 AM.

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#6 Raymond Ramlow

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Posted 07 June 2018 - 03:14 PM

48P/Johnson is still considerably fainter than expected (using Seiichi Yoshida's formulas as a reference). I imaged it today with iTelescope T12 and it was magnitude 14.6-14.7.

 

Meanwhile, I estimated C/2016 M1 to be magnitude 8.3 with a 13' coma. I determined the magnitude of the brightest part of the coma (roughly 4-4.5') to be 8.9, which is pretty much in line with a number of visual estimates from the past few days.



#7 Carl H.

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Posted 10 June 2018 - 12:44 PM

Raymond, thanks for the update on 48P and C/2016 M1. 

 

Looks like C/2016 M1 possesses a large outer coma (probably gaseous) that isn't being seen by most visual observers. Over the past two weeks I have consistently estimated a coma diameter between 3' and 4' and total magnitude mainly between 8.9 and 9.1. 

 

C/2016 M1 (PANSTARRS)
2018 Jun 10.36 UT: m1= 8.9, Dia.=4', DC=5; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)
2018 Jun 08.35 UT: m1= 9.3, Dia.=4', DC=5; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)
2018 Jun 06.32 UT: m1= 9.0, Dia.=4', DC=5; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)

2018 Jun 04.27 UT: m1= 9.0, Dia.=4', DC=4; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)

2018 May 27.46 UT: m1= 9.4, Dia.=3', DC=4; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)

2018 May 24.46 UT: m1= 9.1, Dia.=4', DC=4; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)

2018 May 22.46 UT: m1= 9.1, Dia.=3', DC=5; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)



#8 Carl H.

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Posted 23 June 2018 - 04:50 PM

I've may have made my last visual observation of C/2016 M1. The object is getting too low in my sky by the time the Moon has set. Once the Moon is out of the way again in very early July, the comet will be even lower and the Arizona monsoon should be ramping up.

 

It was fun watching this comet glide through the busy star field of Sagittarius. I'd usually spot the comet, make my observation and then scan the region for globulars.

 

C/2016 M1 (PANSTARRS)
2018 Jun 22.38 UT: m1= 8.3, Dia.=4', DC=3; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)
2018 Jun 19.30 UT: m1= 8.5, Dia.=5', DC=5; 30x125 B; Carl Hergenrother (Tucson, AZ, USA)

 



#9 Carl H.

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Posted 23 June 2018 - 05:03 PM

Chris Wyatt of Walcha, Australia has made a visual observation of C/2017 T3 (ATLAS) on June 22.81 UT at a very low solar elongation of 22 deg. 

 

C/2017 T3 ATLAS
2018 Jun 22.81 UT; m1= 9.4; Dia= 2.8’; DC= 4; 25cm L, f:5 (x39) [Chris Wyatt, Walcha, NSW, Australia]
Diffuse coma, moderately condensed. Enhances in Swan Band filter. Low altitude = 5.7°, interference from zodiacal light and twilight.
Comparison stars checked using Tycho-2 data in Guide 9.0; Method= M; Cat= TK

 

This places ATLAS about where we expected it to be brightness-wise (maybe a few tenths brighter than expected) based on CCD observations from earlier in the year. ATLAS will be a southern hemisphere only object and even then only visible at low elevations.



#10 Raymond Ramlow

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Posted 26 June 2018 - 01:53 PM

C/2017 S3 seems to have brightened considerably in the past month. I imaged it for the first time last night and found it to be magnitude 12.3.



#11 Carl H.

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Posted 26 June 2018 - 08:13 PM

Raymond, thanks!

 

I saw your observation as well as Daniel Bamberger's on COBS. I was hoping activity would pick up if it were gas-rich. We'll probably need to wait for more observations before feeling comfortable with the new brightness trend, but 12th magnitude is definitely better than 14th or 15th. 




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