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Xmas Comet 46P Wirtanen

Xmas Comet 46P Wirtanen

Southern Cape Astronomy Club

A chart showing the movement of comet 46P Wirtanen till mid-month is included in one of the images below, as well as a finder chart for December.  Tick marks are at one day intervals until 15 December. At magnitude +5 the comet is easily visible in binoculars, as well as with the naked eye from a reasonably dark sky site (not a light polluted one). Not quite an Xmas comet in the Terry Lovejoy style (see picture below), but still a naked eye one.

Comet 46P Wirtanen is a small short-period comet with an orbital period of 5.4 years. Wirtanen makes a very close (for a comet), approach to Earth on the 16th December, just a few days after perihelion on the 12th December. At around 30 lunar distances (11.5 million km / 7.1 million miles), from Earth, it's the 10th closest approach of a comet in modern times. Predictions are that it could reach naked-eye visibility at close approach with excellent observing conditions. The comet is visible for most of the night, it is near opposition and is visible well before and after close approach. Presently at around Vm +8 (November 2018), it is within reach of small and medium sized telescopes as well as binoculars. The comet belongs to the Jupiter family of comets having aphelia of between 5 and 6 AU. Its diameter is estimated at 1.2 km.

46P/Wirtanen was discovered photographically on January 17, 1948, by the American astronomer Carl A. Wirtanen. The plate was exposed on January 15 during a stellar proper motion survey for the Lick Observatory. Due to a limited number of initial observations, it took more than a year to recognize this object as a short-period comet.

Wirtanen was the original target for close investigation by the Rosetta spacecraft but was unable to meet the launch window and Rosetta was sent to 67P Churyumov-Gerasimenko instead, where Philae made its historic landing.

Latest Observations, Kos Coronaios, Pearly Beach, Western Cape, SA.

I can confirm that 46P is visible with the naked eye from my location, Pearly Beach, Western Cape, 01/12/2018, 10:48 UT (02/12/2018, 12:48 SAST). Comet was easily acquired in 12 x 50 binoculars and after a few minutes of dark adaption and with minimum averted vision, it was visible with the naked eye. Vm around +5 (comparison stars, tau Eri, pi Cet, eta & zet Eri), coma diameter 40', DC, (degree of condensation), between 3 & 4, could not decide, using 12 x 50 binoculars, in out method (Sidgwick).

Xmas Comet 46P Wirtanen

Kos Coronaios

Relocated from Louis Trichardt and now based in Pearly Beach, the Club meets at least once a month for stargazing or observation evenings close to new Moon or during astronomical related events. Membership is open to anyone interested in astronomy, no fees or subs are required. Donations welcome.

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