1:10 PM | *The “comet of the year” to come just in time for the holidays*
Paul Dorian
Yasushi Aoshima of Ishikawa, Japan, took this picture using a 12-inch telescope in mid-October; credit spaceweather.com
Overview
Some astronomers are calling Comet 46P/Wirtanen the “comet of the year” and it is to arrive just in time for the holidays. Around the middle of December, Comet 46P/Wirtanen will come within 11.5 million kilometers of the Earth making it one of the ten closest approaching comets of the Space Age according to spaceweather.com. This comet is likely to be visible to the naked eye for several weeks right through the holiday season and into early 2019.
This table provides a list of known comet close encounters with Earth, for objects whose orbits are known well enough to be confident of the approach distances. Encounters occurring after 1950 are highlighted as the modern era, which signifies the time that scientific studies began to focus on the physics and chemistry of comets, rather than just qualitative descriptions of their behavior. Note that the distance from Earth is not necessarily an indicator of brightness. Of the comets on the modern-era list, only #4 IRAS-Araki-Alcock and #5 252P/LINEAR (and hopefully #10 46P/Wirtanen) reached naked eye brightness, while many of the others were not detected because they were too faint (#8 323P/SOHO).
Source: http://wirtanen.astro.umd.edu/close_approaches.shtml
Details
Comet 46P/Wirtanen is rather dim at this time – similar to a 10th magnitude star – but its large green atmosphere is very noticeable in latest photographs which comes from diatomic carbon (C2) – a gaseous substance common in comet atmospheres that glows green in the near-vacuum of space. The expectation is that the comet will brighten more than 200-fold by the month of December and it could ultimately reach magnitude +3 which should be visible to the naked eye and certainly viewable by binoculars and small telescopes.
Finder chart for Comet 46P/Wirtanen during December 2018
Comet 46P/Wirtanen is a small short-period comet which passes through the inner solar system every 5.4 years. As of mid-October, it was near the orbit of Mars and headed in our direction. Comet 46P/Wirtanen was discovered by Carl A. Wirtanen in 1948 at the Lick Observatory, California via photographic plate. The plate was exposed on 17 January 1948 during a stellar proper motion survey at the observatory. It took over a year before the object was recognized as a short-period comet due to a lack of observations. 46P belongs to a small family of comets that boast a higher level of activity than expected for their nucleus size and they emit more water vapor than they should. This is one of the reasons for added interest in this regular visitor to the proximity of Earth’s orbit.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com