Comet Section        




We are in the midst of a bright comet drought. August and the first half of September saw no comets brighter than ~10th magnitude and it looks like the rest of September and October will see the same unless there is a new bright discovery or outburst. Currently the next comet predicted to brighten above 10th magnitude will be short-period 45P/Honda-Mrkos-Pajdušáková in late December.

Just a bit fainter than 10th magnitude are a number of comets that are viable targets for large aperture visual observers and CCD imagers. Images of a few fainter comets have been submitted to the Comet Section, including 29P/Schwassmann-Wachmann, 53P/Van Biesbroeck, C/2016 A8 (LINEAR) by Charles Bell, Manos Kardasis and John Sabia. The table below is from the main Comet Section webpage and lists comets 12th magnitude or brighter.

New Discoveries

Since the last Comet Section News posting, a number of comets have been discovered. Most are faint though the most recent find comes with an interesting story.

C/2016 R3 (Borisov) – Gennady Borisov found this comet on September 11 with a 0.3-m f/1.5 Genon astrograph + CCD at the MARGO Observatory in the Crimea. It is his 6th comet discovery since 2013. While Gennady and other CCD observers reported the comet at 16th magnitude, experienced observer Alan Hale was able to observe it visually at 13th magnitude. Perihelion will occur on October 10 at 0.45 AU. Unfortunately, C/2016 R3’s elongation is ~30° and dropping fast in the morning sky. It is possible this comet will only be observable for another week since it will be too close to the Sun to be observed when bright.

Interestingly, the orbit of C/2016 R3 (Borisov) is very similar to that of C/1915 R1 (Mellish). The 1915 comet was discovered by John E. Mellish, purported early observer of craters on Mars and namesake of the Martian crater Mellish. It was one of five comets discovered by Mellish and his second of 1915. With perihelion in 1915 being on October 13, it had almost the exact same, and poor, observing circumstances as in 2016. So far orbit computers have not been able to positively link the 1915 and 2016 observations for orbit periods of ~100, 50, 25 and 20 years. There is no doubt that the 1915 and 2016 comets are related though they may be separate components of a splitting event. The faintness of the 2016 comet relative to the 1915 comet also suggests that the two may be different.

C/2016 R2 (PANSTARRS) – The Pan-STARRS survey found this 19th magnitude comet with their 1.8-m Pan-STARRS1 telescope in Hawaii on September 7. It is a long-period comet with an inclination of 58° and perihelion at 2.64 AU from the Sun in May of 2018. It could brighten to 13th magnitude in 2018.

C/2016 Q4 (Kowalski) – Richard Kowalski discovered this 18th magnitude comet on August 30 with the Mount Lemmon 1.5-m. It is a Centaur-type comet with an inclination of 7°, period of 69 years and perihelion in January of 2018 at 7.1 AU from the Sun. It could brighten by another magnitude between now and perihelion.

C/2016 Q2 (PANSTARRS) – Discovered on 2016 August 26 at 21st magnitude by Pan-STARRS. It is a long-period comet with an inclination of 63° and perihelion is not till 2020 January 3 at 3.43 AU from the Sun. It could brighten to 12-13th magnitude in 2019/2020.

C/2016 P4 (PANSTARRS) – Discovered on August 7 at 22nd magnitude by Pan-STARRS. It is a long-period comet with an inclination of 30° and perihelion on October 16 at 5.89 AU from the Sun. Magnitude 22 is as bright as this comet will get.

P/2016 P2 (PANSTARRS) – Discovered on August 8 at 21st magnitude by Pan-STARRS. It is a short-period comet with a period of 9.3 years. Perihelion was back in November of 2015 at 3.12 AU. This comet will not get any brighter.

P/2016 P1 (PANSTARRS) – Discovered on August 1 at 22nd magnitude by Pan-STARRS. It is a short-period comet with a period of 5.8 years. Perihelion was back in September of 2015 at 2.28 AU. This comet will also not get any brighter.

C/2016 N6 (PANSTARRS) – Discovered on July 14 at 20th magnitude by Pan-STARRS. It is a long-period comet with an inclination of 106° and perihelion on 2018 July 18 at 2.67 AU from the Sun. It may reach 14th magnitude during 2018.

Also the following periodic comets were recovered and numbered.

343P/NEAT-LONEOS = P/2016 P3 = P/2003 SQ205 [T = 2017 Jan 27, q = 2.28 AU, P = 12.8 yrs, expected peak mag = 17]

342P/SOHO = P/2016 N5 = P/2011 E1 = P/2005 W4 = P/2000 O3 – [T = 2016 Jul 1, q = 0.05 AU, P = 5.3 yrs, expected peak mag = very faint outside of SOHO FOV]

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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