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Happy Holidays from Comet 46P/Wirtanen

At only 30-lunar distances from Earth, Comet 46P/Wirtanen brightened to magnitude 3.6 as it brushed by our planet on December 16th — just 4-days after perihelion (closest to sun). The anticipation of this close pass-by engaged the attention of many amateurs that observed and imaged this “dirty-snowball” in the weeks leading up to the fly-by.  But the most iconic image of this comet’s apparition was made two-weeks before its closest approach to Earth.

46P/Wirtanen, Moon Size Comparison by flickr user Mike Broussard. All rights reserved. Used by permission. Imaged with Tele Vue-85 APO and Tele Vue TRF-2008 0.8x Reducer/Flattener for f/5.6. Camera used was Canon T3 with IDAS-LPS (Light Pollution) filter. Exposure at ISO 3200 for 40×120 sec. Image taken Dec 2, 2018 at 03:05 UT.

Mike Broussard’s impressive composite image compares the diameter of the comet to  the full-moon. It quickly spread across the Internet and was featured as the cover image for on December 4th and 5th (as well as on their December 4th newsletter). The image was created with his Tele Vue-85 APO equipped with a Tele Vue TRF-2008 0.8x Reducer/Flattener using a Canon T3  DSLR with IDAS-LPS (Light Pollution) filter. Exposure at ISO 3200 for 40×120 sec was taken Dec 2, 2018 at 03:05 UT. More details on the creation of this image in on his The December Comet– 46P/Wirtanen blog post. 

Motion of Comet 46P/Wirtanen by Mike Broussard. All rights reserved. Used by permission. Imaged with Tele Vue-85 APO and Tele Vue TRF-2008 0.8x Reducer/Flattener for f/5.6. Camera used was Canon T3 with IDAS-LPS (Light Pollution Filter). Frames: 1 minute each at ISO 6400 on December 11, 2018.

The video above shows the comet show moving over the course of an hour.  More video shot a week later was equally impressive. Mike was featured in our Imaging the Skies with the TV-85: Mike Broussard blog post last year.

The comet is named after American astronomer Carl Wirtanen who discovered it on a photographic plate taken at the Lick Observatory in January 1948. At aphelion (furthest from sun), 46/P reaches the orbit of Jupiter and the gravitational tug of the giant planet has shortened the orbital period from 6.8-years in 1912 to 5.4-years today. On the next approach of Wirtanen in 2023, the comet will get no closer to Earth than 2-A.U.  — so enjoy the view now while you can.

Comet Wirtanen by Tom Corstjens. All rights reserved. Used by permission. “Two tails can be discerned, with several faint details in the central coma using averted view.” Alkaid 16″ f/4.2 Dobsonian with Tele Vue Paracorr coma corrector and Delos 17.3mm (115x) with Baader Neodymium contrast enhancing filter. Sketched Dec 12, 2018, from Hombeek, Belgium.

From his sub-rural location in Belgium, Tom Corstjens made a careful study of 46/P with his 16″ Dobsonian equipped with Tele Vue Paracorr to tame the coma inherent in the fast f/4.2 mirror. Using a Tele Vue Delos 17.3-mm eyepiece, with a contrast enhancing Neodymium filter,  he was able to discern two tails and details in the comet’s coma that are displayed on this December 12th sketch. Sketches like this can show more details  than stacks of images. Tom’s sketches were featured on our blog earlier this year in The Art of  Deepsky Sketching at the Eyepiece.

Comet 46P/Wirtanen by flickr user Mark Kilner. (CC BY-NC-SA 2.0). Used by permission. Tele Vue-60 APO refractor and Canon EOS 80D DSLR on Vixen Super Polaris mount using an 18-min exposure at ISO 1600. Taken December 9, 2018 from Broadstairs, Kent on the English coast. “This comet is in a hurry. The star trails show how much it moved during the time I was shooting.”
Showing the versatility of our smallest scope, Mark Kilner tracked the comet for 18-minutes for the above image.  It’s shot with a DSLR attached to his Tele Vue-60 APO refractor.  

Comet 46P/Wirtanen (animation) by flickr user Mark Kilner licensed by (CC BY-NC-SA 2.0). Used by permission. “Sequence of raw frames showing Comet Wirtanen’s progress over a period of 30 minutes (9 Dec 2018, 20:51 – 21:21). The bright star in the lower left is 94 Ceti, a triple-star system with a planet and a dust disc, and – presumably – lots of comets of its own.”
Mark’s images have been featured several times on our blog, most recently in an August post: Tele Vue TV-60: Surprisingly Versatile Mini APO Refractor.
Comet 46P/Wirtanen will continue to be a great target for northern hemisphere observers for a while longer. The moon will interfere with observations this week, but should depart the early-evening sky for the last week of the year.

There is keen interest among astronomy professionals to study  Wirtanen as it is a likely target for future exploration by spacecraft. (Due to it’s periodic appearance and perihelion distance being just outside Earth’s orbit.) In fact, it was the original target for the European Rosetta mission before launch delays caused the re-targeting of that mission to comet 67P/Churyumov–Gerasimenko. 

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