W hile there has been no lack of planetary activity to enjoy in the night sky including visibility of Venus, Jupiter and Mars - one celestial spectacle has been missing for a long time. We have not had a bright comet for a dozen years or so and any that have shown up have required telescopes or binoculars to see. We are long overdue for a really bright comet and although I would like to report otherwise, the comet predicted for Christmas will be a good comet, but not likely a spectacular one. However, as one famous comet hunter, David H. Levy said, “Comets are like cats: they have tails and do precisely what they want.”
Of all celestial objects, comets are the most elusive and most unpredictable. Astronomers know many of their orbits with high precision, but their behaviour when these chunks of frozen ice and gas get near the Sun is much less certain. Many do not brighten on schedule, some break up or get destroyed by a close pass to the Sun and others burst forth in spectacular fashion. The most famous example of a much-ballyhooed comet that flopped was Comet Kohoutek in 1973. I tried more than once to catch a glimpse of Kohoutek and failed, and my better half notes (with glee) that she spotted it casually during a snowmobile ride on a frozen lake in the Peterborough area (that was in our pre-courting days, so it does not really count).
As in the case of Comet Kohoutek, comets can be a complete fizzle, or they can totally defy predictions and be easily seen even from our brightly-lit cities.
The last such comet was Comet Hale-Bopp in 1997 with a spectacular show for over a year, remaining visible to the naked eye for 18 months. But who remembers Comet Hyakatake? This one appeared a year before Hale-Bopp, had a larger tail, and came closer to Earth (a close shave of only 15 million kilometres) than the 200 million km. wide pass of HaleBopp. Unfortunately Hyakatake only appeared for three months in 1996 during typically cloudy spring weather and you had to be dedicated to spot it. I had learned a lesson with Kohoutek, and thankfully, the weather cooperated, so I did observe and photograph it on several occasions.
This Christmas, Comet 46/P Wirtanen is expected to appear in our skies. Away from city lights and moonlight, it may be an interesting sight. Due to be brightest during the later part of 2018 and early January 2019, predictions (for what those are worth) are that it may get to be visible to the naked eye - but don’t expect another Hale-Bopp.
Comet 46/P Wirtanen was preceded by another - a summer comet, Comet Giacobini-Zinner, which required a telescope to see. There is a great picture of it taken by one of our Bluewater Astronomical Society imagers on the BAS website. If predictions are borne out, Comet 46/P will be better than Comet G-Z and should peak late in the year and be best during Moon-free periods in the first two weeks of December and again in the first part of January, 2019. Full Moon occurs Dec. 22 and Wirtanen will not likely be seen over the bright moonlight. But if you can dodge the moon by waiting for it to set, Wirtanen will be above the horizon all night long from midDecember into the New Year. For a chart showing the path of 46/P from Dec. 1, visit the BAS website: www. bluewaterastronomy.com. Click on the VIS.COMETS tab to go to the comets information page.
Good luck with your comet viewing!
On a less happy note, this will be my last astronomy column appearing in local newspapers of the Postmedia Network. However, I will continue a weblog on astronomical happenings at the BAS website. The weblog will include more complete information with charts, links to videos and other graphics as well as some of the spectacular images taken by BAS members (including an occasional one of mine). A direct link to the weblog is http://www. bluewaterastronomy.info/blog/.
Thank you, gentle readers, for all the kind comments I have received over the last three years and 104 columns on astronomy. It has been my pleasure to share my interest with you and it will continue on the weblog. Do check it out.