Comet Section        




Evening Comets

10P/Tempel 2 [Perihelion on 2015-Nov-14 at 1.42 AU from the Sun]

Ernst Wilhelm Liebrecht Tempel, a German astronomer, discovered comet 10P/Tempel 2 in 1873 from Milan, Italy. 2015 marks the comet’s 27th return since discovery and 23rd observed return. The comet has been observed at every return since 1946. This time around, 10P is an evening object moving through Sagittarius (Dec 1-5) and Capricornus (6-31). Recent observations suggest a brightness between magnitude 9.5 and 10.0.

C/2014 S2 (PANSTARRS) [Perihelion on 2015-Dec-09 at 2.10 AU from the Sun]

C/2014 S2 (PANSTARRS) is at perihelion on the 9th at 2.10 AU from the Sun. This comet has been an easy object in my 30×125 binoculars with a strongly condensed coma and a hint of a tail. Located in Draco at declinations between +65 and +61 degrees, it is a circumpolar object for northern observers and observable throughout the night. With little change in its distance from the Sun (2.10 to 2.12 AU) and Earth (1.91 to 1.92 AU), its brightness should stay around magnitude 9.0 for the remainder of December.

C/2013 X1 (PANSTARRS) [Perihelion on 2016-Apr-20 at 1.31 AU]

Yet another Comet PANSTARRS, C/2013 X1 is fainter than S2 but may become much brighter as it approaches its April perihelion. Recent visual reports place it between magnitude 10.0 to 10.5. Its rate of apparent brightening may slow down a bit this month as a decrease in distance to the Sun (2.38 to 2.06 AU) is countered by an increase in distance to Earth (1.53 to 1.80 AU). Still, the comet should be between magnitude 9.5 and 10.0 this month. The comet is nicely placed in the evening as it moves through through Andromeda (Dec 1-9), Pisces (9-13), Andromeda again (13-29) and Pegasus (29-31).

Unlike C/2013 US10 (Catalina) (more on it below), C/2013 X1 may be a dynamically old comet. Its orbit suggests that possibility as does its brightening trend since discovery. Unlike dynamically new comets which brighten in fits and starts and can even fade though still moving closer to the Sun, X1 has held a steady and healthy rate of brightening for the past two years. If this continues then X1 may become a nice binocular comet at ~6th magnitude between the time of perihelion in late April (1.31 AU from the Sun) and closest approach to Earth in late June (0.64 AU from Earth).

CCD images show a very asymmetrical coma with a northward pointing fan curving into an eastward pointing tail.

Morning Comets

C/2013 US10 (Catalina) [Perihelion on 2015-Nov-15 at 0.82 AU from the Sun]

Comet Catalina currently holds the title of brightest comet in the sky.

The brightest comet in the sky is currently behind the Sun and invisible. This state of affairs will change by the end of the month as C/2013 US10 (Catalina) races north through Virgo (Dec 1-24) and Bootes (24-31). Although its distance from the Sun has been decreasing, the comet has stayed steady at around magnitude 6.5 for the past 3 months. Intrinsically this means the comet has actually faded. What this means for the future is unknown though it is possible the comet experienced an outburst in late July or August and has spent the last few months fading back to “normal”.

Comet Catalina starts the month at 0.87 AU from the Sun and recedes to 1.18 AU. It is still rather far from Earth though this distance will greatly shrink from 1.53 AU to 0.89 AU. Elongation will also improve from 32 to 78 degrees. It you are outside on the morning of the 7th to watch the nice conjunction of Venus and the Moon, take a peak at the comet which is only ~4-5 degrees or so to the left (northeast) of Venus.

CCD images show a two tailed comet. Its gas tail has shown intricate, rapidly changing structure while its dust tail appears to be lagging the comet along its orbit. The position of the dust tail is suggestive of larger particles having been released some months prior to perihelion.

New Discoveries

C/2015 T5 (Sheppard-Tholen) is a Halley-type comet with a 149 year period and rather distant perihelion of 9.3 AU (Feb. 5, 2016), Sheppard-Tholen is very faint and should not get much brighter than its current magnitude 21.6. Befitting such a faint comet, the Subaru 8.2-m telescope in Hawaii was used to find it.

C/2015 V1 (PANSTARRS) is a long period comet coming to perihelion at 4.3 AU in December 2017. Discovered on Nov. 2 at ~19-20th magnitude, it will only brighten up to ~15-16th magnitude near perihelion.

C/2015 V2 (Johnson) is an object to keep on your radar as it may become a nice binocular object in 2017. First seen by J. A. Johnson of the Catalina Sky Survey at 17th magnitude, Comet Johnson will reach perihelion on 2017 June 14 at 1.64 AU and pass within 0.83 AU of Earth within a few weeks of perihelion. A peak brightness of 6-7th magnitude is possible.

C/2015 V3 (PANSTARRS) was first detected by the Pan-STARRS survey on Nov. 2 at 21st magnitude. Within weeks of discovery, the comet experienced an apparent outburst to 18th magnitude. V3 is a long period comet that passed perihelion on Nov. 22 at 4.2 AU from the Sun. It shouldn’t get much brighter but all bets are off if more outbursts occur.

C/2015 V4 (PANSTARRS) is on a ~80 year period orbit. Perihelion is in July of 2016 at 5.6 AU. The comet is unlikely to get much brighter than its current brightness of ~19th magnitude.

C/2015 W1 (Gibbs) is a Catalina Sky Survey find by Alex Gibbs with the 0.68-m Catalina Schmidt telescope. W1 was 18-19th magnitude at discovery on Nov. 18. Perihelion is on May 16 at 2.2 AU. It may brighten another magnitude or two in the coming months.

P/2015 W2 (Catalina) is another Catalina find, this time by J. A. Johnson and G. J. Leonard on Nov. 21. W2 is a short-period comet with a period of ~20 years and passed perihelion at 2.6 AU last September. It is unlikely to get brighter than its current 18-19th magnitude.

P/2015 X1 (PANSTARRS) was first recognized as a comet by Pan-STARRS on images taken on Dec. 1 at 20th magnitude. Pre-discovery observations by Pan-STARRS were found going back to August when the comet was 21-22nd magnitude. On a 6.9-year orbit, this Jupiter-family comet passed perihelion back in October at 2.1 AU.

C/2015 X2 (Catalina) is a runt of a long-period comet. Only a 2-3 weeks from perihelion (Dec. 19 at 1.9 AU) at discovery (Dec. 2), X2 is very faint at 19th magnitude. It is unlikely to get much brighter.

As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates.
- Carl Hergenrother (ALPO Comet Section Coordinator)

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