Comet Section        




Happy New Year! 2017 promises to be a busy year for comet observers as no less than 7 comets are predicted to become brighter than 10th magnitude: 2P/Encke, 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova, 96P/Machholz, C/2015 ER61 (PANSTARRS), C/2015 V2 (Johnson), C/2016 U1 (NEOWISE). Of course there are the comets yet to be discovered as well as the dozens of fainter comets within reach of CCDs.

The last month of 2016 was a productive one for the ALPO Comet Section. CCD imagers continued to monitor a number of comets, both bright and faint, while visual observations were reported for the month’s two brightest comets. While January will see a slow down in visual observations as we lose our two bright comets to the glare of the Sun, the action will pick up again in February.

During December, CCD observers Denis Buczynski, Carl Hergenrother, Efrain Rivera Morales, Richard Owens and John D. Sabia contributed images of the following comets: 2P/Encke, 41P/Tuttle-Giacobini-Kresak, 43P/Wolf-Harrington, 45P/Honda-Mrkos-Pajdusakova, 56P/Slaughter-Burnham, 74P/Smirnova-Cherynkh, 93P/Lovas, 174P/Echeclus, 226P/Pigott-LINEAR-Kowalski, 315P/LONEOS, C/2010 U3 (Boattini), C/2013 US10 (Catalina), C/2015 VL62 (Lemmon-Yeung-PANSTARRS), C/2015 V2 (Johnson), C/2015 X7 (ATLAS), C/2016 N4 (MASTER), and C/2016 T2 (Matheny). Visual comet magnitude estimates were submitted by Carl Hergenrother, John D. Sabia and Willian Souza for 45P/Honda-Mrkos-Pajdusakova and C/2016 U1 (NEOWISE).

The effort to digitize the archives of the Comet Section and place them online continues. Currently the Section Gallery contains over 2300 images and drawings of 215 different comets.

Evening Comets

45P/Honda-Mrkos-Pajdusakova [Perihelion on 2016 December 31 at 0.53 au]

Comet 45P/H-M-P has been brightening as predicted with visual observers placing it at magnitude 7.2-7.3 at the end of December. After passing perihelion on New Year’s Eve, its orbit will carry 45P between the Sun and Earth. As a result, we will lose sight of the comet during the first week of January. Not to worry, the best is yet to come as 45P will become an easily observable object (up to 6th-7th magnitude) in the morning sky starting in early February as it passes within 0.08 au of Earth. This month, its heliocentric distance increases from 0.53 to 0.84 au while its geocentric distance crashes from 0.68 to 0.16 au as it moves through Capricornus (Jan 1-15) and Aquarius (15-31) in the evening sky.

The image below was taken by Richard Owens on December 27.

2P/Encke [Perihelion on 2017 March 10 at 0.34 au]

Comet Encke is back again and making its 63rd observed apparition since it was first seen in 1786. Encke will become a visual object this February as it brightens to 7th magnitude. This month, the comet rapidly brightens from ~13th to 10th magnitude. The Section asks that CCD imagers monitor Encke as it approaches perihelion. Note, that Encke’s appearance depends on what filter is used. The comet may still appear asteroidal in the red while a large gas coma is already detectable in the blue. This month Encke is an evening object moving through Pisces as its elongation drops from 97 to 68 degrees. Its distance from the Sun decreases from 1.39 to 0.91 au while its geocentric distance decreases from 1.42 to 1.26 au.

Morning Comets

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

Jess Johnson of the Catalina Sky Survey discovered this long period comet on November 3, 2015 with the 0.68-m Catalina Schmidt. The comet is inbound with a perihelion of 1.64 au and close approach to Earth at 0.81 au this summer. It is well placed for northern observers through perihelion. Now is a good time for CCD imagers and large aperture visual observers to watch C/Johnson brighten from its current 12th magnitude to a peak of 6-7th magnitude. This month, it is a morning object in Bootes at an elongation that increases from 89 to 96 degrees. It starts the month 2.64 au from the Sun and 2.47 au from Earth. At the end of the month, these values decrease to 2.36 au from the Sun and 2.05 au from Earth.

C/2016 U1 (NEOWISE) [Perihelion on 2017 January 14 at 0.32 au]

Comet NEOWISE is a surprise comet. Only 19th magnitude when discovered in late October, the comet rapidly brightened and was approaching magnitude 8.0 at the end of December. The comet will be lost to most observers during the first week of the month as it moves too close to the Sun. At that time it may be as bright as 7th magnitude. Southern hemisphere observers may be able to pick the comet up again in February though it may already be too faint for visual observation. Northern observers won’t get another shot at NEOWISE till August when it may be too faint even for CCD imagers. This month its distance from the Sun drops from 0.49 au to a perihelion on January 14 of 0.32 au. The distance grows to 0.61 au at the end of the month. Its geocentric distance grows from 0.89 to 1.48 au. Though mostly unseen, C/NEOWISE will travel through Ophiuchus (Jan 1-7), Serpens (7-10), Scutum (10-11), Sagittarius (11-26) and Microscopium (26-31).

New Discoveries

Only one comet discovery was reported in the past month. Yet another interesting asteroid on a very cometary orbit was announced.

C/2016 X1 (Lemmon) is a long-period comet with a large perihelion distance of 7.6 au. It was found by G. J. Leonard with the Mount Lemmon 1.5-m reflector. Even though perihelion will not occur till May of 2019, the comet shouldn’t get much brighter than its current 20th magnitude.

Last month we reported on 2016 VY17, an apparently asteroidal object on a Halley-type orbit. A similar object has been recently announced. 2016 VZ18 is on a long-period comet orbit with a period of ~2700 years. Perihelion will occur in early March at 0.91 au. in early April it will approach to within 0.53 au of Earth. If it remains inactive, VZ18 will not get any brighter than magnitude 20. If it does ‘turn on’, it could become much brighter. CCD observers are encouraged to monitor this object and send your images and photometry to the Comet Section. Who knows, maybe you will be the first to notice VZ18 as an active comet.

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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