ALPO COMET SECTION NEWS FOR OCTOBER 2015
2015-October-03
C/2013 US10 (Catalina) still holds the top spot as brightest comet in the sky, albeit only for southern observers. Even they will lose sight of the comet by mid-month as its elongation decreases. The next brightest comet is 10th magnitude C/2014 S2 (PANSTARRS) which is located in the northern circumpolar sky. While pickings are slim for small aperture observers, large aperture owners have a number of faint 10th-12th magnitude comets to visually observe or image. They include C/2013 X1 (PANSTARRS), a faint ~11th magnitude object that will be a nice small telescope/binocular object for much of 2016.
Evening Comets
C/2013 US10 (Catalina) [Perihelion on 2015-Nov-15 at 0.82 AU from the Sun]
Comet C/2013 US10 (Catalina) continues as the brightest comet in the sky though its visibility is limited to the southern hemisphere. October will bring more of the same but even southern observers will lose sight of the comet as its elongation decreases from 47° to 11°. ALPO contributor Willian Souza of Brazil continues to find C/2013 US10 around magnitude 6.5. Last month, it may have experienced a small outburst which would explain why it brightened so quickly to magnitude 6.5. Since then the comet hasn’t shown much change in brightness even though it is still approaching perihelion.
This month Catalina moves through Centaurus (Oct 1-19) and Hydra (19-31) as its heliocentric distance decreases from 1.17 to 0.87 AU and geocentric distance increases from 1.61 AU to 1.82 AU. The comet should be a faint naked eye object from November through January when it will be well placed for northern comet watchers. It is already a nice photogenic object as seen in the below image from Minos Kardasis.
C/2014 S2 (PANSTARRS) [Perihelion on 2015-Dec-09 at 2.10 AU from the Sun]
A bit of a surprise comet, C/2014 S2 is around magnitude 10.0-10.5. It is located in the northern circumpolar sky as it moves from Cepheus (Oct 1-4) into Ursa Minor (4-31) and gets closer to the Sun (2.25 to 2.15 AU) and Earth (1.92 to 1.87 AU). This PANSTARRS comet may still have another magnitude of brightening before it peaks late this year.
22P/Kopff [Perihelion on 2015-Oct-25 at 1.56 AU from the Sun]
Comet Kopff’s 2015 perihelion passage is its 16th since its discovery in 1919. In fact it has never been missed at an apparition since discovery. This month Kopff is around 10th magnitude as it moves through Libra (Oct 1-5), Scorpius (5-12) and Ophiuchus (12-31). It reaches perihelion on October 25 at 1.56 AU. Though its heliocentric distance doesn’t change much this month, it will slowly move away from Earth (1.99 to 2.12 AU).
C/2014 Q1 (PANSTARRS) [Perihelion on 2015-Jul-06 at 0.31 AU from the Sun]
Back in July, C/2014 Q1 peaked at around 4th magnitude. Unfortunately it was never an easy comet to see visually from the northern hemisphere. The latest magnitude estimates from mid-August placed the comet at magnitude 12 and steadily fading. This month PANSTARRS should fade from 12th to 14th magnitude as it moves away from both Sun (1.89 to 2.37 AU) and Earth (2.39 to 3.02 AU) against the stars of Centaurus (Oct 1-2), Lupus (2-26) and Norma (26-31). Due to its far southern location in the sky, views of the comet are limited to southern observers.
C/2014 Q2 (Lovejoy) [Perihelion on 2015-Jan-30 at 1.29 AU from the Sun]
The other bright ‘Q’ comet of the past year is C/2014 Q2 (Lovejoy). Much fainter than at its 4th magnitude peak, Lovejoy is still holding on at ~11-12th magnitude as it moves through Corona Borealis (Oct 1-9) and Hercules (9-31). Its distance from the Sun (3.46 to 3.78 AU) and Earth (3.76 to 4.28 AU) continues to increase as it retreats into the outer solar system.
Morning Comets
C/2013 X1 (PANSTARRS) [Perihelion on 2016-Apr-20 at 1.31 AU]
I was able to observe C/2013 X1 visually on September 25 at magnitude 12.8. This month the comet will brighten another half to full magnitude as it cruises through Auriga (Oct 1-22) and Perseus (22-31) and moves closer to the Sun (3.02 to 2.70 AU) and Earth (2.65 to 1.85 AU). Discovered back in December of 2013, X1 is still over 6 months from perihelion and 8 months from its closest approach to Earth (0.64 AU in late June). This comet should be a nice small telescope object as it stays brighter than magnitude 10 for much of 2016. Peak brightness may be around magnitude 6 or 7 next June.
67P/Churyumov-Gerasimenko [Perihelion on 2015-Aug-13 at 1.24 AU]
Comet 67P/Churyumov-Gerasimenko is the target of ESA’s Rosetta mission. Earth-based observers can watch 67P as it moves through Leo this month. The comet is now past perihelion and will move from 1.38 to 1.57 AU from the Sun while holding steady at around 1.80 AU from Earth. I was able to observe 67P visually on September 25 at magnitude 11.5.
141P/Machholz [Perihelion on 2015-Aug-25 at 0.76 AU from the Sun]
141P is one of many discoveries by former ALPO Comet Section Coordinator Don Machholz. A short-period comet with a 5.25 year period, 141P is making its 5th perihelion passage since its 1994 discovery. During 1994 the comet was actually a multiple comet with 5 components (component D was even observed to split during the apparition). This year the primary (A) has been seen as well as another component provisionally designated component H but may, in fact, be a reappearance of components B, C or D. Hopefully additional astrometry will confirm H as one of the older components or a brand new one.
The comet was predicted to get as bright as 10th magnitude this year but had been severely lagging that prediction. Component A is now around 12th magnitude with component H a few magnitudes fainter. Comet Machholz is already past perihelion and will be moving away from the Sun (0.98 to 1.31 AU) and Earth (1.38 to 1.58 AU) this month. Though the comet(s) should fade rapidly, split comets are notorious for exhibiting erratic behavior so close attention is warranted. It is a morning object as it moves through Leo (Oct 1-8) and Sextens (8-31).
New Discoveries
P/2015 Q2 (Pimental) is a short period comet with a 19 year period. Perihelion occurred on September 15 at 1.82 AU for this 17th magnitude comet. It was discovered by Eduardo Pimental on August 24 as part of the SONEAR survey with a 0.45-m f/2.9 reflector located in Oliveira, Brazil. P/2015 Q2 will not get any brighter this apparition.
P/2015 R1 (PANSTARRS) is a short-period comet found by the Pan-STARRS survey on September 8 at 18th magnitude. It has a 14 year period and passed perihelion back on June 25 at 2.17 AU. It will also not get much brighter.
P/2015 R2 (PANSTARRS) was found by Pan-STARRS a night after they found P/2015 R1. Perihelion was on June 8 at 2.47 AU. The comet is on a 9.5 year orbit and will not get brighter than its current 20th magnitude.
C/2015 R3 (PANSTARRS) is yet another Pan-STARRS find. It was found on September 12 at 20th magnitude. R3 is well passed its 2014 February 12 perihelion which occurred at 5.24 AU from the Sun.
As always, the Comet Section is happy to receive all comet observations, whether images, drawings or magnitude estimates.
- Carl Hergenrother (ALPO Comet Section Coordinator)
