ALPO COMET SECTION NEWS FOR JANUARY 2016
2016-January-02
Happy New Year and Welcome to 2016!
Before looking at the comets visible this month, let’s recap 2015. The Comet Section received 252 positive magnitude estimates of 19 different comets. A total of 555 images and drawings of 67 different comets were also submitted this past year though this number includes observations taken prior to 2015 but only recently archived with the ALPO. The brightest observed comet was C/2014 Q2 (Lovejoy) at magnitude 3.7 with C/2015 G2 (MASTER) and C/2013 US10 (Catalina) tied for second place at magnitude ~6.0-6.1.
Evening Comets
10P/Tempel 2 [Perihelion on 2015-Nov-14 at 1.42 AU from the Sun]
Comet 10P/Tempel 2 has a long observational history stretching back to its discovery from Milan, Italy in 1873. The current apparition marks its 23rd observed return since then. This month 10P is an evening object moving through Capricornus (Jan 1-6) and Aquarius (6-31). It will be a tough object as its elongation decreases from 41° to 34°. Now ~2 months past perihelion and moving away from the Sun (1.50 to 1.64 AU) and Earth (2.10 to 2.36 AU), 10P should see its brightness fade from its current 10-11th magnitude.
C/2014 S2 (PANSTARRS) [Perihelion on 2015-Dec-09 at 2.10 AU from the Sun]
C/2014 S2 (PANSTARRS) passed perihelion on December 9th at 2.10 AU from the Sun. Even with the distant perihelion, it is now bright enough to be seen in binoculars and small telescopes under dark skies. As has been the case for the past few months, S2 is a northern circumpolar object located in Draco at declinations between +61 and +66 degrees. It is observable all night long for northern observers though it is much better placed in the morning. The comet is slowly moving away from the Sun (2.12 to 2.19 AU) and a little closer to Earth (1.92 to 1.86AU) so its brightness should stay around magnitude 9.0 this month.
C/2013 X1 (PANSTARRS) [Perihelion on 2016-Apr-20 at 1.31 AU]
While C/2013 US10 (Catalina) is the brightest comet this January, C/2013 X1 (PANSTARRS) will probably hold that title within the next month or two. X1 is inbound to a April 20th perihelion at 1.31 AU from the Sun. The comet will get even brighter as it comes within 0.64 AU of Earth in late June. Already visible in small telescopes and binoculars at ~9th magnitude, X1 should be a good comet to observe between now and late February when it gets too close to the Sun. We should pick it up again in April as it brightens to ~6-7th magnitude in June (though it may be too far south for some for a few weeks around close approach).
This month, X1 is an evening object with an elongation dropping from 90° to 50° as it moves through Pegasus. Its distance from the Sun falls from 2.06 to 1.75 AU while its distance from Earth increases from 1.80 to 2.22 AU.
Morning Comets
C/2013 US10 (Catalina) [Perihelion on 2015-Nov-15 at 0.82 AU from the Sun]
Comet Catalina is a nice 6th magnitude double tailed comet (see the image below by Manos Kardasis). At the start of January, it is located a few degrees north of Arcturus. If you are out watching the Quadrantids, remember to take a look for this comet. While US10 doesn’t rise till around 1am at the start of the month, its northern motion makes it circumpolar for most northern observers by mid-month as it moves through Bootes (Jan 1-8), Canes Venatici (8-14), Ursa Major (14-20), Draco (20-22), Ursa Minor (22-23), Draco (23-25), Camelopardalis (25-28), Draco (28-30) and Camelopardalis (30-31).
Comet Catalina starts the month at 1.18 AU from the Sun and recedes to 1.59 AU. It is still rather far from Earth though this distance will greatly shrink from 0.89 AU to 0.72 to 0.89 AU.
New Discoveries
Since the last Comet Section News posting, nine comets were discovered. While it may seem that PANSTARRS is finding most of the comets these days, December did see a nice variety in discovery teams.
P/2015 X3 (PANSTARRS) was first seen on December 1 with the 1.8-m Pan-STARRS 1 telescope on Haleakala. It was 20th magnitude at discovery and will probably not get much brighter. A short period comet with a 11.3 year period, X3 passed perihelion back in August at 2.82 AU.
C/2015 X4 (Elenin) was found by Leonid Elenin of Russia with the 0.4-m ISON-NM astrograph in Mayhill, NM, USA on December 3. Discovered at 18th magnitude, it was reported as bright as 16th magnitude in the weeks after discovery. The latest Elenin is a Halley-type comet with a period of 77 years and perihelion of 3.40 AU on November 3, 2015.
C/2015 XY1 (Lemmon) was first seen as an asteroidal object by J. A. Johnson on December 4 with the Mount Lemmon 1.5-m located north of Tucson, AZ, USA. Follow-up observations with the same telescope found the object to be cometary. XY1 is a long-period comet with a perihelion distance of 8.1 AU (T = 2018 March). Currently around 19th magnitude it will only brighten by another magnitude or so by 2018.
C/2015 X5 (PANSTARRS) was surprisingly found over 2 years after perihelion. Perhaps this shouldn’t be too surprising since X5 has spent the past few years at far southern declinations where there are no active large aperture professional asteroid surveys (though there are many smaller aperture surveys trying to fill the gap). First seen on December 6th with the 1.8-m Pan-STARRS1 telescope, the comet was ~20th magnitude. It may have been as bright as 16th magnitude when it was near perihelion in September 2013 at 3.9 AU.
P/2015 X6 (PANSTARRS) has a typical Main Belt asteroid orbit and is probably another example of a Main Belt Comet, also referred to as an Activated Asteroid. Whether its ‘cometary’ activity is due to a recent impact or true ice-driven cometary activity is still TBD. The object was first seen on December 7 with the same telescope that found the other PANSTARRS objects. Perihelion will be on 2016 March 10 at 2.30 AU. It has an orbital period of 4.5 years and aphelion of only 3.2 AU. It was a faint 21st magnitude at discovery and probably won’t get brighter.
C/2015 X7 (ATLAS) is the first comet discovery by the Asteroid Terrestrial-impact Last Alert System (ATLAS) team. ATLAS is a new survey to detect small asteroids prior to impact. This project will undoubtably uncover many more new comets during the course of its search for small asteroid impactors. X7 was 17th magnitude when found with the ATLAS 0.5-m f/2 telescope at Haleakala, Maui, Hawaii, USA on December 12. Perihelion will be on 2016 July 28 at 3.67 AU from the Sun when it should still be around 17th magnitude.
C/2015 X8 (NEOWISE) is a space-based find with the NEOWISE (formally just WISE) satellite in low Earth orbit. X8 is another Halley-type object with a period of 77 years and perihelion distance of 1.19 AU (T = 2015 October 22). Visual observers have seen the comet as bright as 11-12th magnitude. It will quickly fade as it recedes from the Sun.
C/2015 Y1 (LINEAR) was found with the 3.5-m Space Surveillance Telescope operated by the LINEAR team on Atom Peak at White Sands, NM, USA. Found on December 16 at 18th magnitude, Y1 is a long-period comet that will brighten a little before passing perihelion on 2016 May 15 at 2.5 AU.
C/2015 YG1 (NEOWISE) is another NEOWISE find and yet another Halley-type object. It has a period of 78 years and passed perihelion in late September at 2.07 AU at ~16th magnitude.
As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates.
- Carl Hergenrother (ALPO Comet Section Coordinator)
