A Cosmic Christmas Present for 2018

Christmas 2018 brings a very special treat for those of us who look skyward!  If you prefer your seasonal lighting to be of the celestial type, well this year you are in luck and its all because of a comet.

Comet 46/P Wirtanen, December 7th 2018, Credit: Martin Mobberley.

Comet 46/P Wirtanen is not a new comet.  In fact like most comets it’s very old indeed and likely dates back to the very earliest days of our solar system.  It is however relatively new to us as it was first discovered in 1948 by Carl Wirtanen at Lick Observatory.  Like all comets its name derives from its discoverer.

Comet Wirtanen is a short period comet.  It makes one orbit of the Sun every 5.4 years. It’s orbit takes it out as far as Jupiter and at closest approach to the Sun it lies just outside Earth’s orbit

Orbit of Comet 46/P Wirtanen (Wikipedia)

The above animation shows us very clearly why this years passage of Comet Wirtanen is so special.  The time the comet makes its closest approach to the Sun is also close to the time when it is closest to Earth.  In fact when 46/P is closest to Earth on December 16th it is a mere 11.58million kms away.  On a local scale that sounds a lot, but on a cosmic scale that is a mere stones throw.  A comet only 30 times the distance to the Moon at the same time it is closest to the Sun (perihelion) makes a very special Christmas treat for us astronomers.  Don’t worry if you don’t get to see comet Wirtanen on December 16th as it will still remain visible for some time to come.  Certainly well into 2019.

You may well be asking, how do I get to see this wonderful comet and where do I look?  Will I need telescopes or binoculars?  If you live in an urban location and have light polluted skies you will almost certainly need at least a pair of binoculars to track down 46/P.  If you are lucky enough to live in a very dark area with little or no light pollution you should be able to see this without optical aid from mid December until  around the second week in January.  Even those if us who have to live under city skies need not miss out.  Use the finder chart below to find the position of Comet Wirtanen and hunt it down with a pair of binoculars.  You won’t need anything special.  A typical pair of 10×50 binoculars will do just fine.

Finder Chart for Comet 46/P Wirtanen Credit: Raheny Observatory

To use the chart above, face south just after sunset.  Locate familiar constellations and use these to home in on the comets location based on the chart above.  Note that around December 16th Comet Wirtanen is very close to the “Pleiades” star cluster.  So close in fact, you will be able to see both in the same binocular field of view

Position of 46/P Wirtanen on December 16th.  Credit Raheny Observatory

Unfortunately our Irish weather has conspired so that no pictures of this comet have been captured at Raheny.  However it is hoped that some nice images will be captured over the next few days and of course do check back as all of these images will be published here.