Two comets are now making news in astronomical circles as they continue their journey through our Southwestern Iowa skies as well as the solar system.
First in line is a comet that goes by the unusual name Comet Machholz-Fujikawa-Iwamoto that was discovered by three amateur astronomers, 1 in America and 2 in Japan. Second in line is Comet 46P/Wirtanen that was discovered 70 years ago by Carl A. Wirtanen who was, at the time, working at the Lick Observatory in California.
The discovery of Comet Machholz-Fujikawa-Iwamoto is fairly unusual since the discovery of a comet by amateur astronomers is a rare event nowadays because robotic Near-Earth-Object search programs usually catch them first.
Comet Machholz-Fujikawa-Iwamoto was discovered on November 11th and since that time has quadrupled in brightness. It is now glowing at a fuzzy 8th magnitude but is not yet visible to observers in our area. This comet appears to be a first time visitor to the inner solar system and is now plunging toward the sun.
Fresh comets like this one are notoriously unpredictable. They can surge in brightness, seeming to promise a spectacular display, when suddenly they fizzle.
Because of this unpredictability, no one knows if Comet Machholz-Fujikawa-Iwamoto will even become a naked eye object. Stay tuned!
Instead of being detected visually as most comets are, Comet Wirtanen was actually recorded on a photographic plate that was exposed on January 17, 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.
As of today, Comet Wirtanen is slightly below our local southern horizon and can’t be seen, but as December progresses it will continue its northern motion bringing it into view with moderate size backyard telescopes.
Have no fear, however, as this comet’s brilliance is expected to change dramatically.
Comet Wirtanen belongs to a family of these celestial nomads, which are noted for a higher level of activity than expected for their nucleus size. They also emit more water vapor than they should and these unusual characteristics are producing added interest as this visitor comes into the proximity of Earth’s orbit.
While now visible in moderate sized backyard telescopes that is expected to change drastically after Sunday, December 16 when Wirtanen will reach that point in its orbit known as perihelion placing it closest to the Sun, Following that perihelic event, the comet is expected to increase in brilliance, possibly reaching a magnitude 3 that would place it well within the visual acuity of the human eye.
So, where will the comet be in our Southwest Iowa skies?
After December 16, look for the comet in the mid-high eastern sky where it will be positioned very close to the well-known cluster of stars, Pleiades in the constellation of Taurus. From there, the comet progresses toward the northeast moving into the constellation of Auriga.
If skies permit, look for Wirtanen on Saturday, December 22 sitting right next to the very yellowish-white star Capella, brightest star in Auriga.
One problem observing this comet will be the moon. December’s full moon occurs on the 23rd and may make it necessary to put nay comet viewing on hold for a day or two.
No worry, however, Comet Wirtanen will continue to move in the northern sky towards Ursa Major and be visible will into 2019.
Two unique things I should mention about Wirtanen is its color and the fact it has no tail.
At the present time it is has a very noticeable green color to it that’s caused by the comet’s vaporizing nucleus, which emits diatomic carbon C2, a gas that glows green in the vacuum of space. Whether a tail will form is anyone’s guess.