Comet Section        

 
 

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 T1 (ATLAS) – It is questionable whether or not this comet will be observable and, if so, how bright it will be this month. C/2017 T1 (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 30×125 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)

 
 

ALPO COMET NEWS FOR MAY 2018

2018-May-1

Hello Comet Observers!

May brings our first comet brighter than magnitude 10 since January as C/2016 M1 (PANSTARRS) should brighten to 9th magnitude. An assortment of short- and long-period comets will be between 10th and 12th magnitude this month as well. Also provided are updates on other comets expected to become bright later this year.

Bright Comets (magnitude < 10)

C/2016 M1 (PANSTARRS) – For the first time since January, a comet is predicted to become brighter than magnitude 10. C/2016 M1 was discovered by the Maui, Hawaii based Pan-STARRS survey on June 22, 2016. At that time the comet was 19th magnitude and located 7.7 AU from the Sun. Since then the comet has brightened to between magnitude 9.9 and 10.8 as reported over the past week. C/2016 M1 is still inbound to a August 10 perihelion at 2.21 AU and should brighten by another magnitude this month to between magnitude 9.0 and 9.5. Due to its 91 degree inclination orbit, the comet will be moving slowly southward from a May 1st declination of -9 degrees to -23 at the end of the month. It will continue to brighten into June though it will become a more difficult object for northern observers as it moves south.

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 rapidly 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. G-Z may be too faint for visual observation this month. CCD imagers can watch it brighten from 15th to 13th magnitude this month. It will continue to brighten and peak around magnitude 7 in early September.

48P/Johnson - 48P/Johnson has a rather large perihelion distance (2.00 AU) for a (relatively) bright short-period comet. Perihelion 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.

66P/du Toit - The month’s brightest short-period comet appears to be running brighter than predicted. Visual observers have been estimating it to be between magnitude 11 and 12 while CCD imagers have it as bright as magnitude 10. It is possible that CCD imagers are detecting a large faint gaseous coma that is being missed visually. Even though my prediction below has the comet brightening to magnitude 10.3 around its May 19 perihelion (at 1.29 AU from the Sun), the comet may look fainter to most observers. Northern observers may have issues observing du Toit as it is still located far south at declinations of -39 to -31 degrees. This marks 66P’s 4th observed and best apparition since its discovery in 1944 by South African astronomer Daniel du Toit.

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 passes perihelion on May 2 at 2.60 AU. It approaching solar conjunction though its location well 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. C/2016 R2 will spend the month between magnitude 11 and 12 while C/2016 N6 will be between 12 and 13.

C/2017 T3 (ATLAS) – Comet Atlas will not be observable from the ground this month as it will be too close to the Sun. It will once again become visible in late June / early July from the southern hemisphere as a 8th-9th magnitude object.

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
2018-05-01  11.6   05 15  +43 26   2.604   3.217    44E   Aur
2018-05-11  11.7   05 34  +45 15   2.602   3.283    40E   Aur
2018-05-21  11.7   05 56  +46 56   2.605   3.339    37E   Aur
2018-05-31  11.8   06 19  +48 28   2.612   3.385    34E   Aur

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
2018-05-01  12.3   07 48  +59 03   2.792   2.940    71E   Lyn
2018-05-11  12.3   07 48  +54 30   2.763   3.056    63E   Lyn
2018-05-21  12.4   07 51  +50 20   2.738   3.173    55E   Lyn
2018-05-31  12.4   07 56  +46 30   2.717   3.286    48E   Lyn

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
2018-05-01  15.1   19 41  +18 33   1.969   1.578    96M   Sge
2018-05-11  14.5   19 56  +22 52   1.877   1.430    99M   Vul
2018-05-21  13.9   20 11  +27 36   1.784   1.293   100M   Vul
2018-05-31  13.3   20 27  +32 43   1.692   1.169   101M   Cyg

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
2018-05- 1  10.1   19 42  -09 22   2.495   2.048   104M   Aql
2018-05-11   9.8   19 38  -13 00   2.445   1.835   115M   Sgr
2018-05-21   9.5   19 31  -17 44   2.399   1.641   127M   Sgr
2018-05-31   9.2   19 17  -23 44   2.357   1.477   141M   Sgr

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
2018-05-01  14.2   21 04  -15 45   2.161   1.974    86M   Cap
2018-05-11  13.8   21 21  -15 21   2.133   1.842    92M   Cap
2018-05-21  13.4   21 37  -15 04   2.108   1.714    98M   Cap
2018-05-31  13.0   21 52  -14 58   2.086   1.592   104M   Cap

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
2018-05-01  10.7   21 42  -39 02   1.313   0.912    86M   Gru
2018-05-11  10.4   22 32  -37 00   1.295   0.898    85M   Gru
2018-05-21  10.3   23 15  -34 13   1.290   0.896    84M   Scl
2018-05-31  10.5   23 51  -31 07   1.300   0.902    85M   Scl

Other Comets of Interest

In last month’s ALPO Comet News, two low-activity comets were introduced. The first, (3552) Don Quixote, is still designated as 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 through Aquarius and Cetus in the morning sky.

The other object is low-activity comet 364P/PANSTARRS. Discovered in 2013, 364P 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. It is similar to other usually inactive comets that are only active near or within 1 AU of the Sun (such as 169P/NEAT, 249P/LINEAR and 300P/Catalina). This year perihelion occurs on June 24. If its activity is similar to 2013’s, May should see 364P’s activity ramping up resulting in a 17th magnitude object at the start of the month brightening to 14th magnitude by month’s end.

(3553) 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
2018-05-01  15.8   23 48  -21 37   1.243   1.528    54M   Aqr
2018-05-11  15.8   00 16  -15 34   1.241   1.520    55M   Cet
2018-05-21  15.8   00 40  -09 31   1.252   1.515    55M   Cet
2018-05-31  15.9   01 02  -03 33   1.277   1.511    56M   Cet

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
2018-05-01  17.3   08 36  +32 39   1.160   0.712    82E   Cnc
2018-05-11  16.3   08 41  +29 23   1.060   0.668    75E   Cnc
2018-05-21  15.1   08 48  +25 28   0.968   0.611    68E   Cnc
2018-05-31  13.8   08 55  +20 40   0.890   0.538    61E   Cnc

The later part of 2018 will see a few other comets reaching magnitude 10 or brighter. So far no observations have been published for 38P/Stephens-Oterma (peak around 9th mag in Nov/Dec) and 64P/Swift-Gehrels (peak around 10th magnitude in Oct/Nov) by the Minor Planet Center. In the case of 38P this is because it has been close to the Sun though the first observations should come in this month (though still fainter than 18th magnitude). 64P must be fainter than 20th magnitude to not have been seen yet.

Dynamically new and intrinsically faint C/2017 S3 (PANSTARRS) has shown a very slow intrinsic brightening since its September 2017 discovery. It will reach a small perihelion distance of 0.21 AU on August 15. Though the comet will be located too close to the Sun at that time, the hope was it would become bright (7th-8th magnitude) before becoming lost in the glare of the Sun. So far the comet has brightened to 17-18th magnitude so there is still some question as to whether it will be a visual object prior to perihelion. Being intrinsically faint and dynamically new there is also a real possibility that this comet is small and will disintegrate at it nears the Sun.

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 MARCH 2018

2018-March-03

Will March be a good month of comet observing? The answer depends on the aperture of your telescope and whether you are a visual or CCD observer. The bad news, unless a surprise discovery or outburst occurs, is that no comet this month will be an easy object for small telescope visual observers. The good news is large aperture visual observers and CCD imagers have quite the varied selection of objects to observe.

This month I decided to try a different format for these monthly summaries. I’m hoping the new format makes it easier to quickly identify observing targets. The comets will be broken down into three categories: comets brighter than magnitude 10, comets between magnitudes 10 and 13, and fainter comets of interest. In some cases, the comet of interest may no longer be visible but is the subject of recent research such as this month’s discussion of long-lost (or is it?) D/1770 L1 (Lexell).

Information for each comet is now presented in tabular form. This information includes the comet’s designation and name, date of perihelion (T), perihelion distance (q), and type of orbit (JFC for Jupiter family comet with period, HFC for Halley family comet with period, LPC-DO for dynamically old long-period comet, LPC-DN for dynamically new long-period comet). At 10 day intervals, the predicted magnitude, rough J2000 RA and Dec position, heliocentric distance, geocentric distance, elongations from the Sun (E for evening object, M for morning object) and constellation is shown.

Bright Comets (magnitude less than 10)

C/2017 T1 (Henize) – This intrinsically faint comet appears to have survived long enough to reach its February 21 perihelion passage at a rather small 0.58 AU from the Sun. As additional astrometric observations were made, the Minor Planet Center orbits for Heinze oscillated between a dynamically old and dynamically new solution. The latest orbit (released on Feb 28 with positions extending through Feb 12) shows Heinze to be dynamically new. Intrinsically faint, dynamically new objects are prone to fade rapidly after perihelion or even completely disintegrate. This is definitely a comet to keep an eye on. Unfortunately that won’t be easy as the comet starts the month close to the Sun. By the 2nd half of the month, Heinze will be far enough away from the Sun to be more easily seen though by then it may be a difficult visual object and also only visible from the southern hemisphere at that time.

C/2017 T1 (Heinze)      T = 2018-Feb-21  q = 0.58 AU	LPC-DN
Date       Mag     RA    DEC     r   delta  elong const
March 01    10   21 36 +10 19   0.60  1.32   25M   Peg
March 11    11   21 39 +03 17   0.69  1.40   27M   Aqr
March 21    12   21 45 -03 31   0.83  1.43   34M   Aqr
March 31    13   21 53 -10 13   0.98  1.43   43M   Cap

Faint Comets (between magnitude 10 and 13)

While there may not be any comet brighter than 10th magnitude this month, there are quite a few comets between magnitudes 10 and 13. In fact, there are seven comets in that brightness range.

C/2016 R2 (PANSTARRS) – The highlight of the bunch remains the ‘blue comet’. No not the famed Jersey Central passenger train, but comet C/2016 R2 (PANSTARRS). This comet is rich in CO+, or the carbon monoxide ion, which gives it a dynamic ion tail and blue color. The comet is still approaching its May 2nd perihelion. Its increasing comet-Earth distance will more than counter the shrinking heliocentric distance so a slow fade should occur this month. Recent magnitude estimates are still scattered but seem to be around 10th to 11th magnitude.

C/2015 O1 (PANSTARRS), C/2015 M1 (PANSTARRS), C/2016 N6 (PANSTARRS) – These three comets are similar to C/2016 R2 in that they are all PANSTARRS discoveries and have relatively large perihelion distances at 3.73, 2.21 and 2.67 AU, respectively. Recent observations place M1 at around magnitude 11 to 12.6. The other two are in the 12th to 13th magnitude range. O1 (for part of the month) and N6 (for the entire month) are northern circumpolar objects so both will be invisible for southern hemisphere observers.

62P/Tsuchinshan and 185P/Petriew – Both of these comets are now past perihelion. Making its 4th observed return, 185P/Petriew is now over a month past perihelion and slowly fading from 12th to 13th magnitude in the evening sky. 62P/Tsuchinshan should be fainter as it fades from 13th to 14th magnitude.

66P/du Toit – This year brings the 4th observed return of 66P/du Toit. Discovered in 1944 by South African astronomer Daniel du Toit, the comet was also seen at its returns in 1974 and 2003 but missed in 1959 and 1988. It is currently on an orbit with a 14.7 year period. This return will see its closest approach to Earth since its 1944 discovery apparition. The comet-Earth distance will still be a rather distant 0.90 AU. As a result, 66P may only brighten to 11th-12th magnitude. During its 2003 return, it rapidly brightened in the months prior to perihelion so this month may see the comet start at 17th magnitude and then brighten to 13th magnitude by month’s end. It will be a difficult object for northern observers due to its southern declination.

185P/Petriew T = 2018-Jan-27  q = 0.93 AU JFC  P = 5.5 yr
Date       Mag     RA    DEC     r   delta  elong const
March 01    12   02 04 +04 31   1.04  1.34   50E   Psc
March 11    12   02 52 +06 52   1.11  1.38   52E   Cet
March 21    12   03 28 +08 49   1.19  1.45   54E   Tau
March 31    13   04 21 +10 18   1.28  1.54   55E   Tau

C/2016 R2 (PANSTARRS) T = 2018-May-02  q = 2.60 AU   LPC-DO
Date       Mag     RA    DEC     r   delta  elong const
March 01    10   04 03 +30 20   2.71  2.61   84E   Tau
March 11    10   04 09 +32 42   2.68  2.72   76E   Per
March 21    11   04 18 +34 59   2.66  2.84   69E   Per
March 31    11   04 29 +37 11   2.64  2.95   62E   Per

C/2016 N6 (PANSTARRS)   T = 2018-Jul-18  q = 2.67 AU    LPC-DO
Date       Mag     RA    DEC     r   delta  elong const
March 01    12   15 15 +77 36   3.03  2.62  105E   UMi
March 11    12   12 19 +80 20   2.98  2.60  103E   Cam
March 21    12   10 01 +79 03   2.94  2.61   99E   Dra
March 31    12   08 43 +74 49   2.90  2.65   93E   Cam

62P/Tsuchinshan         T = 2017-Nov-16  q = 1.28 AU JFC  P = 6.4 yr
Date       Mag     RA    DEC     r   delta  elong const
March 01    13   14 33 +02 35   1.78  1.04  123M   Vir
March 11    13   14 31 +03 22   1.85  1.02  133M   Vir
March 21    14   14 26 +04 11   1.92  1.02  143N   Vir
March 31    14   14 17 +04 54   1.98  1.04  153M   Vir

C/2015 O1 (PANSTARRS)   T = 2018-Feb-19  q = 3.73 AU    LPC-DN
Date       Mag     RA    DEC     r   delta  elong const
March 01    12   16 25 +39 11   3.73  3.44   99M   Her
March 11    12   16 14 +43 03   3.73  3.34  105M   Her
March 21    12   15 58 +46 56   3.73  3.27  110M   Her
March 31    12   15 37 +50 33   3.74  3.23  113M   Boo

66P/du Toit             T = 2018-May-19  q = 1.29 AU    JFC  P = 14.9 yr
Date       Mag     RA    DEC     r   delta  elong const
March 01    17   16 54 -29 02   1.65  1.41   84M   Oph
March 11    16   17 29 -32 11   1.57  1.28   86M   Sco
March 21    15   18 10 -35 10   1.50  1.16   88M   Sgr
March 31    13   18 57 -37 41   1.44  1.07   88M   CrA

C/2016 M1 (PANSTARRS)   T = 2018-Aug-10  q = 2.21 AU    LPC-DO
Date       Mag     RA    DEC     r   delta  elong const
March 01    11   19 14 +01 10   2.86  3.33   53M   Aql
March 11    11   19 22 +00 04   2.80  3.15   60M   Aql
March 21    11   19 29 -01 07   2.73  2.94   67M   Aql
March 31    11   19 35 -02 31   2.67  2.73   75M   Aql

Other Comets of Interest

D/1770 L1 (Lexell) – This comet holds a few distinctions. One, it was the first Jupiter family comet to be recognized as such. Two, it holds the record for closest observed cometary approach to Earth at 0.015 AU or 5.8 lunar distances. Three, it was named not after its discoverer but its orbit computer (similar to 1P/Halley, 2P/Encke and 27P/Crommelin). Four, it was discovered by famed French comet hunter Charles Messier. Five, it hasn’t been seen since.

Quan-Zhi Ye (Caltech), Paul A. Wiegert (Western Ontario) and Man-To Hui (UCLA) have recently published their investigation into the whereabouts of Comet Lexell. They found that even though the comet has experienced numerous close approaches to Jupiter, there is a high probability that the comet still has a perihelion distance of &lt; 3 AU and a close to even probability of having a perihelion distance of &lt; 1 AU. A search of known comets turned up no possible linkages to Lexell but a search of known near-Earth asteroids did find a few possibilities. The authors identified NEA 2010 JL33 as the most likely object to be long-lost, and now inactive, Comet Lexell. 2010 JL33 is a dark (albedo of 0.047) object with a diameter of ~1.8 km which is consistent with a cometary nucleus. JL33’s next perihelion will occur in July 2019 at 0.71 AU. The object will be faint at 19th magnitude at that time and poorly placed at an elongation of 41 degrees.

A pre-print of the paper can be found at https://arxiv.org/pdf/1802.08904.pdf .

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 – JANUARY 2018

2018-January-1

Happy New Year! and Welcome to 2018. This year promises to be an exciting year for the Comet Section. New discovery C/2017 T1 (Heinze) is already bright enough for small telescope observers. Later in the year, the following comets should also become nice small telescope targets: 21P/Giacobini-Zinner (magnitude 6 in September), 38P/Stephen-Oterma (magnitude 9 in November), 46P/Wirtanen (magnitude 3 in December), 64P/Swift-Gehrels (magnitude 9 in October/November), C/2017 S3 (PANSTARRS) (magnitude 7 in August though it may get even brighter when too close to the Sun to be observable) and C/2017 T3 (ATLAS) (magnitude 8 in July/August). For large telescope and/or CCD observers, there are many dozens of comets that will become bright enough to observe this year.

Continuing our recent ALPO Comet News format, each release will concentrate on comets that are brighter than 12th magnitude. Fainter comets of interest may also be highlighted. This month four comets are expected to be brighter than 12th magnitude for part of the month: C/2017 T1 (Heinze), C/2016 R2 (PANSTARRS), 185P/Petriew and 62P/Tsuchinshan. At 13-14th magnitude, distant centaur comet 174P/Echeclus is once again in outburst.

Evening Comets

C/2017 T1 (Heinze) [Perihelion on 2018 February 21 at 0.58 au]

The new year kicks off with immediate action courtesy of comet C/2017 T1 (Heinze). As the month begins, you’ll have to battle the first Full Moon of January to see the comet. By the evening of the 2nd or 3rd, there should be enough dark time between the end of twilight and moonrise to grab a quick peak at Heinze. With a closest approach to Earth on January 4 at 0.22 au, the comet should brighten from magnitude 9.2 on the 1st to a peak of around 8.8 a week later. After that the comet will continue to approach the Sun (perihelion on February 21 at 0.58 au) but due to an increase in the comet-Earth distance (from the 0.22 au minimum to 0.79 au at the end of the month) the comet should experience a slow fade to magnitude 9.8 by February 1st.

Recent visual observations of Heinze from December 29 UT with 30×125 binoculars under a LM = 6.0 sky show it to be a rather diffuse (5′) low surface brightness object with little condensation or elongation. It is likely that observers under brighter skies and/or using high magnifications/large apertures will see the comet as much smaller and fainter.

Even with the bright Moon, CCD imagers may want to observe Heinze during the first few days of January. On January 3rd, the Earth passes through the comet’s orbit plane. As a result, the comet’s dust tail will be seen edge on. While dust tails seem to appear to be 3-dimensional tubes of material, in fact, they are usually 2-dimensional sheets. Similar to Saturn ring plane crossings, comet orbit plane crossings are when we are looking directly along the plane of the dust tail ’sheet’. On the days around orbit plane crossing, the dust tail will appear to narrow and may even grow in length as the surface brightness of the tail increases. CCD and large aperture visual observers will also notice the position angle of the tail rapidly swinging from the SSW on the 1st to nearly due east by the 10th.

Comet Heinze was discovered by Aren Heinze with the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey on October 2nd at 18th magnitude. The comet appears to be intrinsically faint. Based on the first few orbits from the MPC, it also appeared to be dynamically new. The latest orbit (released on December 31) make it more likely that Heinze is a dynamically old comet. While faint dynamically new comets have a tendency of not surviving their perihelion passage, faint dynamically old comets should be robust enough to survive. Regardless, all observers are asked to keep a close watch on Heinze as it nears perihelion and to look for any changes in coma morphology that might suggest a splitting or disintegration event.

Heinze will be moving rapidly through the northern evening sky this month. It starts the month in Lynx (Jan 1-3) before moving through Camelopardalis (3-6), Cassiopeia (6-12), Andromeda (12-13), Lacerta (14-22) and Pegasus (22-31). Northern observers should be able to follow Heinze into early February before it gets too close to the Sun. After that it will be too far south for northern observers. Heinze might be glimpsed from mid-latitude observers in the southern hemisphere during the first day or two of January. The comet will again become visible to southern observers in mid to late March about 1 month after perihelion. By then the comet will have faded to 11th magnitude or fainter.

The ephemeris below (and for all following comets) was produced with Seiichi Yoshida’s ‘Comet for Windows’ program with my best estimate of each comet’s photometric parameters. Comet brightness forecasts are prone to error due to sudden outbursts and changes in brightness trends so don’t be surprised if a comet’s brightness deviates from what is shown below. Also it is suggested that you use your favorite online ephemeris generator or planetarium program to determine exact positions for your time of observation.

The image below was taken by ALPO Comet Section contributor Charles Bell on December 29 with a 0.3-m Schmidt-Cassegrain + CCD + R band filter. It consists of 48 x 12 second exposures. Charles maintains a very active and informative Twitter account focused on comet news and observations. I highly recommend it.

C/2016 R2 (PANSTARRS) [Perihelion on 2018 May 9 at 2.60 au]

Comet C/2016 R2 (PANSTARRS) was a bit of a sleeper for much of 2016. A dynamically old long-period comet, it was expected to brighten rapidly as it approached perihelion. Instead the comet intrinsically faded during the first three quarters of 2017. Starting in October, it rapidly brightened from magnitude 14 to 10.7. While not the brightest comet, it has entertained CCD imagers with an intricate and rapidly changing ion tail reminiscent of comets C/1908 R1 (Morehouse) and C/1961 R1 (Humason). All three comets share one trait that may explain their unusual tails, they are all very rich in CO+.

The comet is still about 5 months out from its May 9 perihelion at a rather distance 2.60 au. This month its heliocentric distance will drop from 2.93 to 2.80 au. Any intrinsic brightening will be partially countered by an increasing geocentric distance (increasing from 2.07 to 2.29 au). As a result, the comet should only brighten from about magnitude 10.7 to 10.4 this month. It is very possible that the comet may even fade in apparent magnitude if its recent rapid increase in intrinsic brightness moderates. This month PANSTARRS is an evening object spending the entire month in Taurus.

185P/Petriew [Perihelion on 2018 Jan 27 at 0.93 au]

Jupiter-family comet 185P/Petriew was a visual discovery by Canadian amateur astronomer Vance Petriew with his 20″ dobsonian while star hopping to the Crab Nebula (M1) at the 2001 Saskatchewan Summer Star Party. 185P/Petriew is on an orbit with a period of 5.5 years and is making its 4th observed return this year. With a perihelion distance of 0.93 au, this comet has peaked between magnitude 9 and 12 at each return. This year it should peak at magnitude 11 around the time of perihelion (January 27) and closest approach to Earth (mid-February at 1.33 au) when located in the western evening sky. It is interesting that this comet was not discovered till 2001. Its perihelion was 1.0 au or less for three returns prior to discovery (1984, 1990, 1996). The 1990 return was comparable to this year’s and the 1984 return was much better. For nearly a 100 years before 1984, it perihelion was larger but not by too much (between 1.21 and 1.40 au).

For the current return, few observations of this comet have been reported to, or at least published by, the usual astrometric and photometric archives (MPC, COBS, ICQ, BAA, German Comet Group, ALPO). According to past behavior, 185P should be near magnitude 12.0 at the start of the month and brighten to near magnitude 11.0 by the end of January. Once the Moon leaves the evening sky, it will be interesting to see how bright 185P really is. On January 1, the comet will be located 1.01 au from the Sun and 1.52 au from Earth. These distances drop to 0.94 au from the Sun and 1.36 au from Earth at the end of the month. The comet can be observed moving against the stars of  Capricornus (Jan 1-8), Aquarius (8-31) and Pisces (31).

174P/Echeclus [Perihelion on 2015 April 21 at 5.81 au]

Centaur comet 174P/(60558) Echeclus orbits the Sun on a 35 year orbit that carries it from just outside the orbit of Jupiter to between the orbits of Saturn and Uranus. While not quite as outburst prone as 29P/Schwassmann-Wachmann 1, Echeclus has experienced a number of multi-magnitude outbursts since 2006. Brian Skiff of Lowell Observatory discovered a new outburst of Echeclus on December 7. Over the following days and weeks the object brightened to magnitude 13.5 to 14.0. CCD observers continue to image a slowly expanding cloud of dust. The cloud is expected to continue to expand and slowly fade this month. Echeclus is currently an evening object and can be found in Aries (Jan 1-31).

I was able to remotely image 174P on December 24 with a 0.51-m telescope located at Warrumbungle, Australia. The telescope is part of the Sierra Star Observatory Network.

Morning Comets

62P/Tsuchinshan [Perihelion on 2017 Nov 16 at 1.38 au]

Discovered photographically in 1965, 62P/Tsuchinshan (Chinese for Purple Mountain which is the name of the observatory where the discovery was made) is making its 9th observed return. The comet was observed between magnitude 10.5 and 11.5 from late October into December. This month, its heliocentric distance increases from 1.48 to 1.62 au while its geocentric distance drops from 1.20 to 1.11 au as it moves through Virgo (Jan 1-31) in the morning sky. The comet should fade by nearly a magnitude over the course of the month from around 11.1 to 11.9.

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 – DECEMBER 2017

2017-December-6

The Geminid meteor shower is always a highlight for planetary observers in December. This month also provides a nice opportunity to observe the largest “Geminid” of all, asteroid 3200 Phaethon. The Geminid parent body will brighten to magnitude 10.7 as it passes within 0.07 au of Earth. Another object, 2017 VT14,  that could be cometary based on its orbit, may make a historic close approach to within 0.01 au of Earth though it may be too faint except for CCD imagers. As for active comets, C/2017 T1 (Heinze) will be interesting to watch as it approaches perihelion early next year. This intrinsically faint, dynamically new comet may brighten to 9-10th magnitude this month.

Evening Comets

29P/Schwassmann-Wachmann 1 [Perihelion on 2019 March 7 at 5.77 au]

The 2017 season for observing 29P is drawing to a close as the comet is slowly sinking lower in the wester sky after dusk. The comet continues its elevated activity level and is currently 13th magnitude. CCD imagers are asked to keep monitoring it as long as possible before it is lost till after solar conjunction. 29P is located near the border of Aquarius and Capricornus.

C/2017 O1 (ASASSN) [Perihelion on 2017 Oct 13 at 1.50 au]

The brightest comet of the past few months (that didn’t require a spacecraft to observe) was C/2017 O1 (ASASSN). After obtaining a peak brightness of magnitude 8-9 in September and October, the comet started to fade in November. As seems to be typical for large diffuse comets, there is quite a bit of scatter in the current magnitude estimates with most observers placing it around magnitudes 10 and 11. The comet should continue to fade as it moves away from the Sun (1.64 on Dec 1 to 1.84 au on Jan 1) and Earth (0.95 to 1.23 au). For those wanting to take a look at ASASSN, it will be located in the northern circumpolar sky as it moves through the Milky Way constellation Cepheus this month.

3200 Phaethon [Perihelion on 2017 January 25 at 0.14 au]

Asteroid 3200 Phaethon is the parent body of the Geminid meteor shower. Whether the shower was produced by long-lasting cometary activity or a series of splitting events, the Geminids are now one of the strongest annual showers. Recently Phaethon has been observed to display comet-like activity around perihelion. Due to intense heating (perihelion is 0.14 AU from the Sun or 7 times closer than Earth) some of the rocks on the surface may have fractured producing a cloud of dust which was knocked off the surface by solar radiation pressure. In effect, it is a acting like a “rock comet”. Still these sort of events are very short-lived and produce minimal amounts of debris, hence they are not large enough to create the large mass of existing Geminids by themselves.

This year Phaethon will pass 0.069 au from Earth on December 16 and brighten to magnitude 10.7. While little to no cometary activity is expected, such a close approach does provide an opportunity to directly study the surface of Phaethon via time-resolved and color photometry. Lightcurve, color and phase function photometry are requested for better understanding of this enigmatic object which is now also the target of a proposed Japanese-lead spacecraft mission, Destiny+ (see presentations on Destiny+ here and here). With a rotation period of 3.6 hours, an entire rotation can be observed during a relatively short observing session. This is the closest approach to Earth by Phaethon since 1974 (0.055 au) and till 2093 (0.020 au). Phaethon starts the month 1.25 au from Sun, 0.31 au from Earth and V magnitude 13.7. It rapidly moves across the evening sky constellations of Auriga (Dec 1-11), Perseus (11-14), Andromeda (14-17), Pegasus (17-19), Aquarius (19-21) and Capricornus (21-31) before ending the month at 0.73 au from Sun and 0.29 au from Earth.

2017 VT14 [Perihelion on 2017 Dec 11 at 0.98 au]

Phaethon won’t be the only “is it a comet or asteroid” object passing close to Earth this month. Though its orbit suggests no relationship to Phaethon, 2017 VT14 will pass close to Earth only hours after Phaethon.

2017 VT14 was discovered on November 13 by the NEOWISE satellite in low Earth orbit. As of November 23, when it was last observed, this object has not shown any cometary activity. Its orbit is similar to a Jupiter family comet and backwards integration of the orbit uncovers a number of recent close approaches to Jupiter. VT14 will pass 0.0098 au from the Earth on December 17. If it is recognized as a comet, it may make the closest cometary approach in recorded history. Comet D/1770 L1 (Lexell) passed within 0.0151 au of Earth in 1770. Only one other comet may have come closer though it is based on a very poorly determined orbit (C/1491 B1 at 0.0094 au).

VT14 starts the month at 0.99 au from Sun and 0.10 au from Earth. Perihelion occurs on December 11 at 0.98 au. By the end of the month, VT14 will be located 1.02 au from Sun and 0.09 au from Earth. If it remains inactive, it will start the month at V magnitude 20.5, peak at 16.0 on December 17 and end the month at 19.6. If it becomes active, it could be many magnitudes brighter.

The object will quickly move through the following constellations: Pegasus (Dec 1-12), Aquarius (12-15), Sculptor (15-16), Phoenix (16), Tucana (16-17), Hydrus (17, Horologium (17), Dorado (17-18), Volans (18), Carina (18-19), Vela (19-21), Pyxis (21-22), Antlia (22-31), and Hydra (31). It will be lost to most northern hemisphere observers just hours to days before closest approach. CCD observers are encouraged to closely watch this object for any sign of cometary activity. Similar to Phaethon, this is also a great opportunity to acquire lightcurve, color and phase function photometry for this object.

Morning Comets

24P/Schaumasse  [Perihelion on 2017 Nov 16 at 1.21 au]

Short-period comet 24P/Schaumasse is making its 11th observed return since its discovery back in 1911 by French astronomer Alexandre Schaumasse. Perihelion occurred last month on November 16 at 1.21 au and closest approach to Earth on November 21 at 1.46 au. On November 26, I saw 24P with my C14 at 98x at magnitude 11.2. It was small (2.5′) with a diffuse coma and no sign of a tail. This month, comet Schaumasse should slowly fade from magnitude 11 to 12 as it moves through Leo (Nov 1-8) and Virgo (8-30). Now past its November 16 perihelion, Schaumasse will recede from the Sun (1.22 to 1.34 au) and Earth (1.46 t o 1.50 au) this month.

62P/Tsuchinshan [Perihelion on 2017 Nov 16 at 1.38 au]

Discovered photographically in 1965, 62P/Tsuchinshan (Chinese for Purple Mountain which is the name of the observatory where the discovery was made) is making its 9th observed return. The comet was observed between magnitude 10.5 and 11.0 for much of late October into November. On November 26, I observed 62P with my C14 at 98x at magnitude 10.8. Similar to 24P, 62P was small (2′) with a diffuse coma and no sign of a tail. This month, its heliocentric distance increases from 1.39 to 1.47 au while its geocentric distance drops from 1.29 to 1.20 au as it moves through Leo (Nov 1-26) and Virgo (26-30) in the morning sky.

C/2017 T1 (Heinze) [Perihelion on 2018 February 21 at 0.58 au]

C/2017 T1 (Heinze) is a recent discovery by Ari Heinze with the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey on October 2nd at 18th magnitude. Perihelion will be on February 21 at 0.58 au. The comet appears to be intrinsically faint but due to a small perihelion distance and a pre-perihelion close approach to Earth in early January at 0.22 au, it is possible that this comet may brighten to magnitude 9.5 to 10.0 by the end of this month. If Heinze is going to get that bright, it better get a move on. While we haven’t received any observations of Heinze in November, recent observations submitted to COBS show the comet had only brightened to 15th magnitude by the end of November.

This will be an interesting comet to watch this month. A dynamically new and intrinsically faint comet, Heinze may not survive its perihelion passage. CCD imagers (and if it brightens further, visual observers) should keep this comet under close watch. Heinze starts the month at 1.70 au from the Sun and 1.08 au from Earth. By the end of the month, the comet is much closer to the Sun (1.21 au) and Earth (0.25 au). It moves through Hydra (Dec 1-17) and Cancer (17-31) this month.

C/2016 R2 (PANSTARRS) [Perihelion on 2018 May 9 at 2.60 au]

C/2016 R2 (PANSTARRS) reaches perihelion in May at 2.60 au from the Sun. For much of 2017, C/2016 R2 showed little increase in activity. That all changed last month as the comet brightened from 14th to 11th magnitude. This month, PANSTARRS should continue to brighten as its perihelion distance drops from 3.09 to 2.94 au and it geocentric distance drops from 2.14 to 2.05 au before increasing back to 2.07 au. The comet passes though opposition this month as it moves against the stars of Orion (Dec 1-16) and Taurus (16-31).

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.

- Carl Hergenrother (ALPO Comet Section Coordinator)

 
 

ALPO COMET NEWS – NOVEMBER 2017

2017-November-5

The brightest comet of the month will probably not be observed directly by anyone from Earth as 96P/Machholz will remain too close to the Sun after its October perihelion. The brightest nighttime comet should be C/2017 O1 (ASASSN) as it fades from 9th to 10th magnitude. The second and third brightest nighttime comets should be returning periodic comets 24P/Schaumasse and 62P/Tsuchinshan. While 24P is predicted to be brighter (at magnitude 10.5 vs 11.5), observations during October suggest that 62P may be the one that brightens to magnitude 10.5 with 24P being fainter.

Evening Comets

29P/Schwassmann-Wachmann 1 [Perihelion on 2019 March 7 at 5.77 au]

Outburst prone 29P/Schwassmann-Wachmann has been quite active this year. The comet has been consistently observed between magnitude 11 and 14 since September. How bright it will be this month depends on whether it experiences another outburst. This is one comet where rapid changes in brightness and coma morphology make day-to-day (and sometimes even hour-to-hour) monitoring worthwhile. CCD imagers are especially asked to keep a watch on this enigmatic object as it slowly drifts near the Capricornus/Aquarius border in the evening sky.

C/2017 O1 (ASASSN) [Perihelion on 2017 Oct 13 at 1.50 au]

As November starts, the brightest comet in the night sky is C/2017 O1 (ASASSN). Due to this comet’s diffuse and large coma, a large range of magnitude estimates has been reported. Binocular observers have reported the comet to be between magnitude 8.5 and 9.0 while larger telescope observers have reported the comet to be as faint as magnitude 10.5. In my 30×125 binoculars, ASASSN is large (7-8′), very diffuse and hard to detect as anything more than a faint brightening against the background sky. It could be easy to miss under a Moon-lit or light polluted sky. This month the comet should fade as it is moving away from the Sun (1.52 to 1.64 au) and Earth (0.75 to 0.95 au). For those willing to take a look at ASASSN, it will be located in the northern circumpolar sky as it moves through Camelopardalis (1-15) and Cepheus (15-30).

Morning Comets

24P/Schaumasse  [Perihelion on 2017 Nov 16 at 1.21 au]

Short-period comet 24P/Schaumasse is making its 11th observed return since its discovery back in 1911 by French astronomer Alexandre Schaumasse. Perihelion occurs this month on November 16 at 1.21 au and closest approach to Earth on the 21st at 1.46 au. The comet was expected to peak at 10-11th magnitude this month. Recent visual observations show it to be running 1-2 magnitudes fainter than predicted. At the end of October, the comet was between 12-13th magnitude. Whether it brightens to 10th magnitude remains to be seen but it is very possible that Schaumasse may not get brighter than 11-12th magnitude. this month as it moves through Leo (Nov 1-8) and Virgo (8-30). Its next return in late 2025/early 2026 will be better with a close approach to Earth of 0.59 au.

62P/Tsuchinshan [Perihelion on 2017 Nov 16 at 1.38 au]

While 24P/Schmaumasse underperforms, 62P/Tsuchinshan appears to be a brighter than expected. Discovered photographically in 1965, 62P/Tsuchinshan (Chinese for Purple Mountain which is the name of the observatory where the discovery was made) is making its 9th observed return. The comet was observed between magnitude 10.5 and 11.0 at the end of October. It should brighten by another 0.5 to 1.0 magnitude as it reaches perihelion on Nov 16 at 1.38 au. This brightness would match 62P’s performance at its return in 1985. Looking ahead, its next return in late 2023/early 2024 will be even better with a lower perihelion distance (1.26 in 2023 vs 1.38 au this year) and geocentric distance (0.50 au in 2023). This month, its heliocentric distance stays around 1.38 au and its geocentric distance drops from 1.41 to 1.29 au as it moves through Leo (Nov 1-26) and Virgo (26-30) in the morning sky.

New Discovery

The last Comet Section post introduced two recent discoveries that should become bright enough for visual observers, C/2017 T1 (Heinze) and C/2017 T2 (PANSTARRS). The ATLAS survey, which also discovered C/2017 T1, has found another comet which should become bright in 2018. C/2017 T3 (ATLAS) was discovered on October 14 at 18th magnitude. The comet is currently in the far northern sky in Cepheus at a distance of 3.8 au from the Sun. It comes to perihelion on 2018 July 19 at 0.83 au. Unfortunately, it does not get too close to Earth (1.35 au on August 1) though it is possible that this dynamically old long-period comet will brighten to magnitude 9 or 10 around perihelion.

Mike Olason imaged two of the recent discoveries (C/2017 T1 and C/2017 T2) with his 11″ SCT and SBIG STF-8300M CCD from Colorado.

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.

- Carl Hergenrother (ALPO Comet Section Coordinator)

 
 

NEW DISCOVERIES, THE FIRST INTERSTELLAR ASTEROID AND 96P/MACHHOLZ IN SOHO

2017-October-25

Lots of exciting news has broken within the comet community the past few days.

In no particular order…

C/2017 T1 (Heinze) was discovered by Ari Heinze with the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey on October 2nd at 18th magnitude. Perihelion will be on February 21 of next year at 0.58 au. The comet appears to be intrinsically faint but due to its small perihelion distance and a pre-perihelion close approach to Earth in early January at 0.22 au, it is possible that this comet will become bright enough for small telescope observers. Its 97° inclination orbit will make it well placed for northern hemisphere observers pre-perihelion. After perihelion it will only be visible from the southern hemisphere. We don’t know if it is dynamically old or new yet. If it is dynamically new, its intrinsic faintness suggests it could be a candidate for disintegration as it nears perihelion.

C/2017 T2 (PANSTARRS) was first observed by PANSTARRS on September 15 at 20th magnitude. It is currently 9 au from the Sun but will get much closer with a perihelion on 2020 May 5 at 1.62 au. It won’t be too close to Earth when at perihelion (~1.6 au) but could be 8th magnitude and well placed for northern observers during much of 2020. Usually when small perihelion comets are discovered so far out it is because they are dynamically new and hyperactive when far out and inbound. C/2017 T2 appears to be dynamically old so it will be interesting to see how its brightness evolves as it gets closer.

A/2017 U1 is odd. First off, it has an A/ prefix meaning it was originally classified as a comet and then reclassified as an asteroid. Secondly, it has an eccentricity of 1.19! It is very possible that this object was never gravitationally bound to the Sun and is the first definitive interstellar asteroid. With a ‘radiant’ near the solar apex, the orbit is even aligned in the direction expected for most interstellar objects to radiate from (in effect, the direction the solar system car is driving in). With a perihelion of 0.25 au on September 9, the object was first designated as C/2017 U1 (PANSTARRS) since its orbit is very comet-like (even though it is extremely hyperbolic). Deep imaging by Karen Meech (U. of Hawaii) with the Very Large Telescope revealed no apparent cometary activity. While an asteroidal origin at first seems odd, there are estimates that 99+% of our solar system’s asteroids were ejected so it is very possible that there are just as many wandering asteroids as comets in interstellar space. Unfortunately, this object is already 21st-22nd magnitude and rapidly fading. Hopefully the very large telescopes will be able to get some colors and spectra.

Link to Sky and Telescope article on A/2017 U1.

96P/Machholz is now 2 days from its own very close perihelion (0.12 au) and in the field of view of the LASCO C3 coronagraph on the SOHO spacecraft. You can go to the SOHO image site to see the comet entering the FOV at around 5 o’clock. Above, I mentioned that A/2017 U1 was our first definitive interstellar asteroid. Due to 96P’s odd chemical make-up (at least compared to most comets) has led some to suggest that 96P is itself a captured interstellar comet. So while we can’t go out and observe 22nd magnitude A/2017 U1 we can watch soon to be 2nd magnitude 96P from the comfort of our home computer.

96P is visible between the white lines in the lower right of the below SOHO Lasco C3 image.

- Carl Hergenrother (ALPO Comet Section Coordinator)

 
 

ALPO COMET NEWS – OCTOBER 2017

2017-October-1 [updated October-7]

[Coordinator's note: Past Comet Section Coordinator Don Machholz reminded me of an omission in the October ALPO Comet News: one of his discoveries, 96P/Machholz. Though a difficult comet to observe for most observers, it will be visible in SOHO images and should be the brightest comet this month. The text below has been updated to include information on 96P.]

Two comets will be brighter than 10th magnitude this month, 96P/Machholz and Comet C/2017 O1 (ASASSN). Only C/2017 O1 will be brighter than 10th magnitude and easily observable visually. It was hoped that ASASSN would brighten to 7th magnitude but, alas, it looks like magnitude ~9 is as bright as it will get. Short-period comet 24P/Schaumasse should brighten to almost 10th magnitude by the end of the month as it makes its 11th observed return since its discovery in 1911.

Evening Comets

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson remains solely a southern hemisphere object as it moves through Norma (Oct 1-5) and Ara (5-31). Johnson is well past perihelion and is in full retreat from the Sun (2.19 to 2.46 au) and Earth (2.34 to 2.84 au). As a result, the comet is expected to fade from around magnitude 11 to 12 this month.

29P/Schwassmann-Wachmann 1 [Perihelion on 2019 March 7 at 5.77 au]

29P has been very active the past few months. During September it was reported to be as bright as 11th-12th magnitude and seemed to be in a constant state of outburst. This is one comet where rapid changes in brightness and coma morphology make day-to-day (and sometimes even hour-to-hour) monitoring worthwhile. CCD imagers are especially asked to keep a watch on this enigmatic object as it slowly drifts near the Capricornus/Aquarius border in the evening sky.

C/2017 O1 (ASASSN) [Perihelion on 2017 Oct 13 at 1.50 au]

C/2017 O1 (ASASSN) burst onto the scene in July after its discovery by the All-Sky Automated Survey for Supernovae. The comet experienced an outburst in the days following discovery (and possibly even prior to discovery) and rapidly brightened to 9th magnitude. There was hope that the comet would continue to brighten as it approached perihelion and closed in on the Earth. Alas, the comet has actually faded intrinsically over the past month. Its brightness has been steady around magnitude 9.0 to 9.5 as its smaller heliocentric and geocentric distance has counteracted the intrinsic fading. Both myself and Salvador Aguirre have been observing ASASSN visually. In my 30×125 binoculars, the comet possessed a very diffuse 5-6′ coma with little condensation. Salvador also noted the comet to be very diffuse and little condensed in his 0.2-m SCT at 50x. The large diffuse nature of the coma has resulted in differing brightness estimates between myself and Salvador (magnitude 9.0-9.2 in the 30×125s and 10.0-10.4 in the 0.2-m at 50x). This is an object where observing with the smallest aperture instrument (that is also large enough to see the comet) is preferred.

As ASASSN moves northward through Perseus (Oct 1-16) and Camelopardalis (17-31) it is also rising earlier in the night. The comet is high enough to observe by 10-11 pm at the start of the month and is circumpolar by the end of the month. Its heliocentric distance is around 1.50 au all month with perihelion on October 13. It geocentric distance is also fairly steady this month (between 0.72 and 0.77 au). How bright it will get is questionable but short of a new outburst it looks like 9th magnitude is the maximum for this comet.

John D. Sabia imaged C/2017 O1 (ASASSN) on September 26 with a 0.5-m RC from northeast Pennsylvania. While the comet possesses a small condensed dusty component to its coma, the image shows evidence of the much larger diffuse coma seen by visual observers.

Morning Comets

96P/Machholz [Perihelion on 2017 Oct 27 at 0.12 au]

This month’s brightest comet should be short-period comet 96P/Machholz. One of former ALPO Comet Section Coordinator Don Machholz’s visual discoveries, 96P was first seen 1986 and 2017 marks its 7th observed apparition. 96P is also one of the more interesting comets. For starters, it is a short period comet (5.3 year orbital period) with a super low perihelion distance of 0.12 au. It is also a member of the Machholz complex. This complex is made up of related objects that most likely originated from a single progenitor some time in the past. In addition to 96P, the Machholz complex also consists of an asteroid (now 2003 EH1, but may have been an active comet in the past and observed as C/1490 Y1), lots of meteor showers (Quadrantids, daytime Arietids, Northern δ-Aquariids, Southern δ-Aquariids, November ι-Draconids, December α-Draconids, daytime λ-Taurids, θ-Carinids, κ-Velids) and other comets (all of the Marsden and Kracht comet groups). Recent studies of the above mentioned meteor showers suggest the Machholz complex has been active in the inner Solar System since 10,000 to 20,000 BC.

Comet 96P/Machholz will be difficult to observe visually from the ground this year. Northern observers will have no chance to see the comet while observers south of the equator will be able to catch a glimpse of the comet very low in the morning sky during the first half of October. Luckily, 96P will pass through the field-of-view of the SOHO spacecraft’s LASCO C3 coronagraph imager between October 25 and 30. The comet should get as bright as 2nd magnitude at perihelion on the 27th. After perihelion the comet will be too far from the Sun to be seen by SOHO but too close to the Sun to be seen by any Earth-based observers until 2018. Watchers of 96P in the SOHO images should be on the look-out for secondaries of Machholz. The same process that broke up the Machholz complex’s progenitor are still active. During 96P’s last return, two small secondaries were observed in the SOHO images leading the main comet by a few hours.

24P/Schaumasse  [Perihelion on 2017 Nov 16 at 1.21 au]

Short-period comet 24P/Schaumasse is making its 11th observed return since its discovery back in 1911 by French astronomer Alexandre Schaumasse. The comet currently has a 8.25-year period and is being observed for the first time since 2001 having been missed at its last (and poorly placed) apparition in 2009. Perihelion occurs next month on November 16 at 1.21 au and closest approach to Earth only a week later at 1.46 au. The comet is a morning object moving through Cancer (Oct 1-5) and Leo (5-31). Currently 13th magnitude, Schaumasse should brighten to 10.5 by the end of the month.

New Discovery

The Pan-STARRS survey has discovered another comet that may become bright enough for most observers in the summer of 2018. C/2017 S3 (PANSTARRS) is currently 20th magnitude and located at 5.2 au from the Sun. That distance is comparable to the distance of Jupiter though the comet is well north of the Jupiter’s actual orbit at a declination of +78°. Perihelion will occur on August 15 of next year at only 0.21 au from the Sun. It is too early to say much about the brightness prospects of C/2017 S3. Right now, its orbit suggests a dynamically new object meaning it is likely to brighten slowly and may even be too small to survive long past perihelion. Regardless, this is one to watch (mainly with CCDs) over the coming months as it will be observable from the northern hemisphere through early August of 2018. Visual observers may have a small window to observe it in the weeks prior to perihelion. Unfortunately, southern hemisphere observers will miss out on this comet.

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.

- Carl Hergenrother (ALPO Comet Section Coordinator)

 
 

ALPO COMET NEWS – SEPTEMBER 2017

2017-August-31

Comet C/2017 O1 (ASASSN) is the only comet that can be considered bright this month at magnitude ~9 to 10. While pickings are slim for visual observers, CCD observers can image dozens of other comets including outbursting 29P/Schwassmann-Wachmann 1 (magnitude ~ 12.0).

The lack of any bright comets has resulted in few visual magnitude estimates being submitted this August and the majority were non-detections. The Section received visual estimates from Salvador Aguirre and Carl Hergenrother for comets C/2015 ER61 (PANSTARRS) and C/2017 O1 (ASASSN). CCD images were obtained from Gianluca Masi, Mike Olason, Richard Owens, and John D. Sabia for comets (457175) 2008 GO98, 2P/Encke, 49P/Arend-Rigaux, 71P/Clark, 73P/Schwassman-Wachmann 3, 77P/Longmore, 89P/Russell, 139P/Vaisala-Oterma, 145P/Shoemaker-Levy, 174P/Echeclus, 189P/NEAT, 237P/LINEAR, 240P/NEAT, 353P/McNaught, 355P/LINEAR-NEAT, C/2015 ER61 (PANSTARRS), C/2015 O1 (PANSTARRS), C/2015 V2 (Johnson), C/2015 VL62 (Lemmon-Yeung-PANSTARRS), C/2016 M1 (PANSTARRS), P/2016 WM48 (Lemmon), and C/2017 O1 (ASASSN). Most of the above objects were imaged by Mike Olason, a new contributor to the Section. The large number of observed comets is due to his ability to push his 11″ telescope to ~20th magnitude.  An example of his work is the below image of periodic comet 237P/LINEAR, a low activity comet displaying a nice tail from dust released near perihelion. The nearly inactive nucleus is the stellar object near the ‘head’ of the dust tail.

Evening C0mets

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson is only visible from the southern hemisphere where it is well placed for observation as it moves through Lupus (Sep 1-13) and Norma (13-30). Johnson is now 3 months past perihelion and is in full retreat from the Sun (1.96 to 2.19 au) and Earth (1.85 to 2.34 au). As a result, the comet will continue to fade this month from around magnitude 10.0 to 11.0.

29P/Schwassmann-Wachmann 1 [Perihelion on 2019 March 7 at 5.77 au]

29P has been very active this summer with multiple outbursts being detected. As August begins the comet has just experienced another outburst and is as bright as 12th magnitude. Being located out near the orbit of Jupiter, it doesn’t move much from month to month so it remains near the Capricornus/Aquarius border. This is one comet where rapid changes in brightness and coma morphology make day-to-day (and sometimes even hour-to-hour) monitoring worthwhile.

Morning Comets

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

C/2015 ER61 (PANSTARRS) reached perihelion back in May and has faded rather rapidly to between magnitude 11.5 to 12.5. The comet will continue to fade as it moves away from the Sun (2.04 to 2.41 au) and its geocentric distance remains steady at (1.66 to 1.67 au). ER61 is a morning object this month moving through Taurus.

C/2017 O1 (ASASSN) [Perihelion on 2017 Oct 13 at 1.50 au]

Recent discovery C/2017 O1 (ASASSN) should be the brightest comet of the month. In the days after discovery, the comet appeared to be undergoing an outburst and was observed to brighten by a few magnitudes. Since then the comet’s rate of brightening has significantly slowed down. It is currently around magnitudes 9.5 and may brighten to between 8.0 and 9.0 by the end of the month as it approaches both the Sun (1.62 to 1.52 au) and Earth (1.06 to 0.77 au). How bright this comet gets is still in question. It is well placed in the morning sky for northern observers as it moves northeastward through Taurus (Sep 19-27) and Perseus (27-30).

John D. Sabia obtained the image of Comet ASASSN shown below on August 26 UT.

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.

- Carl Hergenrother (ALPO Comet Section Coordinator)

 
 

ALPO COMET NEWS – AUGUST 2017

2017-July-31

When I first started writing this month’s Comet News the focus was going to be on how after 8 months that saw 8 comets reach 10th magnitude or brighter, the rest of the year was going to bring a bright comet drought. While this may still be true, a new discovery provides some hope that this Fall will see at least one come bright enough for most small telescope observers.

Evening C0mets

C/2015 V2 (Johnson) [Perihelion on 2017 June 12 at 1.64 au]

Comet Johnson is no longer visible from the northern hemisphere. By the time it heads far enough north to be seen by most northern observers it will have faded beyond the reach of all visual and most CCD observers. Southern comet watchers will still be able to follow Johnson this month as it moves through Centaurus (Aug 1-25) and Lupus (26-31). Currently around magnitude 9.0, it will fade by another magnitude this month as it moves away from the Sun (1.77 to 1.95 au) and Earth (1.35 to 1.83 au).

71P/Clark [Perihelion on 2017 June 30 at 1.59 au]

Discovered back in 1973, periodic comet 71P/Clark is making its 8th observed return. Similar to the last two months, Clark will spend all month in Scorpius.  Recent reports place the comet between magnitude 10.5 and 11.0. Steady fading should continue as the comet retreats from the Sun (1.62 to 1.69 au) and Earth (0.79 to 1.04 au).

29P/Schwassmann-Wachmann 1 [Perihelion on 2019 March 7 at 5.77 au]

Regular outbursting comet 29P/Schwassmann-Wachmann 1 is now on the evening side of opposition near the Capricornus/Aquarius border. Always active, the comet can reach 12th magnitude during its outbursts. As August begins it is at magnitude 14 and slowly fading after a recent outburst. Monitoring of 29P’s outbursts will help better constrain its rotation period and outburst mechanisms. This is one comet where rapid changes in brightness and coma morphology make day-to-day monitoring worthwhile.

Morning Comets

C/2015 ER61 (PANSTARRS) [Perihelion on 2017 May 9 at 1.04 au]

C/2015 ER61 (PANSTARRS) reached perihelion back in May and has faded rather rapidly to between magnitude 10.5 to 11.5. The comet will continue to fade as it moves away from the Sun (1.69 to 2.04 au) and Earth (1.67 to 1.68 au). ER61 is a morning object this month moving through Taurus.

217P/LINEAR [Perihelion on 2017 Jul 16 at 1.24 au]

217P had a nice apparition last time around in 2009 when it brightened to 9th magnitude. This year’s apparition won’t be as good with it only brightening to 12-13th magnitude. Southern CCD observers will be able to watch it as it moves through Orion all month. The comet is now moving away from the Sun (1.25-1.36 au) and Earth (1.44-1.48 au). CCD observations are especially requested as 217P displayed some interesting jet features in 2009.

C/2017 O1 [Perihelion on 2017 Oct 13 at 1.51 au]

Comet Assassin! No it’s not the name of the latest video game your kids or grandkids are playing, but it is the possible name of a bright comet discovered by the ASAS-SN (All-Sky Automated Survey for Supernovae) project. C/2017 O1 was first seen with the the ASAS-SN quadruple 14-cm “Cassius” telescope on Cerro Tololo, Chile on July 19 UT (discovery Astronomical Telegram #10597). In the first few days after discovery, the comet experienced an outburst to magnitude ~10.5. A report by Erik Bryssinck & F.-J. Hambsch on the comets-ml suggest another small outburst occurred between July 28 and 29 UT.

What the future holds for C/2017 O1 is still unknown. Here is what we do know. C/2017 O1 appears to be a long-period comet though whether it is dynamically new or old is still to be determined. The comet is currently 1.82 au from the Sun and 1.51 au from Earth. Those distances will drop to 1.63 au and 1.07 au by the end of the month. It is a morning comet moving northeast through Eridanus (Aug 1-12), Cetus (12-19) and Taurus (19-31). Perihelion occurs on October 14 at 1.51 au from the Sun and closest approach to Earth on October 17 at 0.72 au. If its current 10th magnitude is indicative of its true brightness (and not just the result of a short-lived outburst), the comet may brighten to 7th-8th magnitude in October. At that time it will also be a northern circumpolar object.

As for the name or lack thereof, the IAU Small Body Nomenclature committee will probably decide on the official name for C/2017 O1 when the next official orbit is released. It will be interesting to see if it will be Comet ASAS-SN, Comet ASASSN or even be named after the human ASAS-SN member who first saw it.

Other Comets in the News

(457175) 2008 GO98

Gianluca Masi and Efrain Morales Rivera have submitted images this past month of comet (457175) 2008 GO98. If (457175) 2008 GO98 seems like a strange designation for a comet, it is. The designation is actually for a numbered asteroid. Between its first reported sighting in 2001 and early 2016, this object didn’t appear to display any cometary activity. All that changed in early 2016 when the object rapidly brightened from 21st to 17th magnitude. Though well observed in 2016, no one noticed the brightening or any cometary features. It wasn’t until July 3rd of this year, that Greg Leonard noticed a coma and short tail in images taken with the Mount Lemmon 1.5-m.

While on an orbit that resembles a member of the Hilda family of asteroids, backward integrations of its orbit show that it has made many close approaches to Jupiter in the past and 300 years ago was on a Centaur orbit entirely exterior to Jupiter. This all suggests that it is not an asteroid that is acting like a comet but rather a comet that mimiced an asteroid for awhile.

International Comet Quarterly

The original clearinghouse of comet photometry and observation has returned after a hiatus of 7 years. The April 2010 issue (ICQ 154) has been published. A free downloadable copy is available at the ICQ website.

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates. Please send your observations via email to < carl.hergenrother @ alpo-astronomy.org >.

- Carl Hergenrother (ALPO Comet Section Coordinator)

Older Posts »

   Powered by WordPress     Personalized by: Larry Owens     Contact the Webmaster