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The Grest Cometr debate Starts!
Fringe_dweller has put the cat in amongst the pigeons, so to speak. This debate has occurred almost everytime in recent memory that there have been contenders for the title.
In the past I have delivered talks on this subject and it is my contention that there are two elements that go either separately, or together, to make up a "Great Comet." They are, in no particular order, 'brightness,' and 'size.'
A sky object/phenomemenon, daytime or night, that has great angular size will always impress most people by that dimension alone. Something small, but very bright (the Full Moon e.g.) will do likewise. Combine the two and there are no arguments (Comet McNaught in Jan 2007).
In 1996 and 1997 we had two very contrasting 'Great Comets.' The unexpected Hyakutake in 1996 put on a display for those who saw it that will not be forgotten. In a rural location like mine the tail was a classic search-light beam like something from a medieval wood-cut drawing, and stretched out to around 70 degrees long from the Northern Hemisphere. Some say that Hyakutake went to 90 degrees, but I can find no photgraphic eveidence to back this up. The coma was a massive 2 degrees across, like a swollen, diffuse full moon. Yet from most cities the tail only stretched out to about 10 degrees at best.
The highly anticipated Hale-Bopp a year later never grew to much more than 25 degrees long at best, but once again a huge coma, slightly brighter than Hyakutake's, followed by a highly reflective dust pume that was easily seen from the greatest cities of the northen hemisphere, meant that H-B was a stand out in the memory of anyone who bothered to glance up at it. Being the longest visible-to-the-naked-eye comet also helped cement H-B as a great comet.
When I started to compare the current size of Lovejoy to the remarkably similar Ikeya-Seki of 1965, the numbers are very much alike. Obviously Lovejoy 2011 W3 doesn't possess a bright coma/nucleus like I-S, but the brilliance, and growing length of the tail certainly makes up for that.
Considering the comments below by Terry himself regarding the comet's perigee date, I would expect the tail to increase significantly, as did LINEAR T7 back in May 2004, as the comet makes its closest approach to earth. If that occurs then we should see the length numbers about the same as those for the great comets of 1880 & 1887.
When we add all of these factors up, as well as the reported magnitude near perihelion passage of -2.9. I will not be surprised if the title of, "Great Comet," is bestowed upon our magnificent celestial Christmas present!
Cheers
Coops
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