“Great” Comets

When it was first  discovered, ISON was being predicted to become a spectacular sight in our sky in late 2013. In that dizzying time, there were some pretty crazy, mega-optimistic predictions being made about sky-spanning tails, a comet “15x brighter than the Moon!” (I have a page on this blog addressing that misconception and how it came aboutingly some lazy arsed journalists and bloggers are STILL parroting that prediction, which was put to rest a long time ago… ), “Visible in broad daylight!” etc etc…

For a brief, wonderful time it looked as if finally, after all the years of waiting, we were going to get to see a genuine “Great Comet” in our sky in our time. There’s a lot of debate about what makes a comet “Great”, and my friend and fellow comet fan Daniel Fischer has some thoughts on that, but personally, in my non-scientific opinion, I think for a comet to be considered “Great” it has to be so impressive to the naked eye, either because it’s spectacularly bright or has a long, long tail, that you don’t need to look for it, it’s just *there*, dominating the sky, painted across it with God’s own brush, slap-across-the-face obvious to even the most inexperienced skywatcher who glances up at the heavens when they come out of the pub or walk their dog last thing at night…

It looks like that’s not going to happen with ISON, sadly. Not because of ISON’s frustrating reluctance to brighten, which has amateur and professional astronomers scratching their heads and pulling their hair out. No. It was probably never going to happen anyway, to be honest. But we might yet get to see a very attractive naked eye comet in December, after ISON rounds the Sun and starts to unfurl its tail like a banner. Curved or straight, long or short, we don’t know what that tail will look like yet; we won’t know until ISON whips around our star and, hopefully, emerges from its glare and begins its drift up into the northern sky.  As I have said so many times on this blog, We’ll Have To Wait And See…

But if ISON isn’t destined to become a Great Comet (and I still have my fingers crossed it might, don’t get me wrong! I’m not giving up on it, unlike some!) what would a Great Comet look like? There will be one in our sky eventually; we’re long overdue a truly Great Comet. The next Great Comet could be discovered literally any day, either by one of the automated telescopes which now finds most comets, or in the old fashioned way, by a patient amateur astronomer, who knows the night sky like the back of his or her hand, who notices a stranger in a familiar starfield, a misty something that shouldn’t be there. And trust me, when the next Great Comet is found, and measurements and observations show that it is destined to be a genuine spectacle in the sky, it will make the ISON fuss look like a quiet Sunday walk on a deserted beach! The world will go absolutely comet crazy. But for the moment, I thought it might be fun – if frustrating! – to take a look at some observer accounts of Great Comets of the past. So I went through my comet books and dug out some passages from them…

From “HALLEY’S COMET AND THE PRINCIPIA” (Peter Lancaster Brown)

Re. the “Great Comet of 1680” (“Newton’s Comet”, which had a 70 degree tail!)

‘One German scholar wrote: “I tremble when I recall the terrible appearance it had on Saturday evening in the clear sky, when it was observed by every-body with inexpressible astonishment. It seems as though the heavens were burning, or as if the very air were on fire…from this little star stretched out such a wonderfully long tail even an intellectual man was overcome with trembling; one’s hair stood on end as this uncommon, terrible and indescribable tail came into view.”

Re. Halley’s Comet seen in 1456

Florentine cosmographer Paolo Toscanelli: “Its head was round and as large as the eye of an ox, and from it issued a tail fan-shaped like that of a peacock. Its tail was prodigious, for it trailed through a third of the firmament.”

Re. Halley’s Comet seen in 1910 (again, possibly a 70 degree tail)

‘On 18 May a London correspondent based in Acra, West Africa, wrote home: “…Here everyone has gone mad over it, and we all get up at 4am, and sit and gaze at it til it gets light. It is the most wonderful thing ever seen. The comet itself rises far above the horizon, but its tail which stands straight up, is like the rays of a very powerful searchlight – so long, that it reaches from the horizon to the very roof of the heavens; and so broad that it occupies roughly one fourth of the arc of the sky; and its light is so powerful that combined with Venus (which is also lovely just now) it has almost the effect of a midnight sun. The natives are frightened to death of it, and will have that it means an earthquake is coming…”

From “COMET OF THE CENTURY” (Fred Schaaf)

Re. Tebbutt’s Comet of 1861

‘Schmidt in Athens made the following report: “On Sunday the 30th of June at 8.30pm a comet of enormous size appeared at the north-western horizon of Athens. The twilight behind Mt Parnassus had not yet faded away whenI was informed, and I can truthfully say no other surprise couldhave made so deep an impression. The night before had been absolutely clear and I had seen no trace of a comet. Now the sky was filled by this majestic figure, spreading the tail from horizon to beyond Polaris and even across Lyra. It was, to use the language of the past, a comet of truly fearful appearance. At 9 o’clock the head of a comet, looking as large as the Moon, was next to Mt Parnassus. The head and the very wide lower part of the tail appeared like a distant fire. After the head had disappeared below the horizon and it had grown dark, one could see that the tail extended to the MIlky Way in the costellation of Aquila. At 11pm I went to the observatory to watch for the reappearence of the head in the northeast… AT midnight and for some time after the tail stood nearly vertically above the northern horizon, its most brilliant portion and the nucleus hidden, the tail reached 30 degrees beyond the zenith [Author’s note: In other words, the tail was more than 120 degrees long!!] At 4.27 am the head of the comet became visible again, following reappearance of the brightest parts of the tail which produced weak but noticeable shadows. Neither the Great Comet of March 1843 nor Donati’s comet of October 1858 had been so bright… I watched the rising of the comet’s head with the naked eye; it was an incredible phenomenon that cannot be compared to anything else. The great mass of light hung like a dull smoky fire over the dark outline of the mountains. As it grew lighter the tail disappeared. I could only see about 4 degrees of arc of the tail at 5.30 am. But at 6.08 am when Capella was the only still visible star the nucleus was still clearly luminous. ”

Wow… I want to see something like that in my lifetime, don’t you? Imagine seeing something like that in the sky. What kind of a fuss would it cause today? People would go nuts, wouldn’t they?

And finally…

Re. The Great Comet of 1882 (Sungrazer, maximum tail length maybe 90 degrees, maximum magnitude between -15 and -20!)

‘The next morning Sir David Gill at the Cape of Good Hope beheld a majestic scene, which he described in a now-famous passage: “There was not a cloud in the sky, but looking due east one saw the tail of the comet stretching upwards, nearly to the zenith, and spreading with a slight curve. Not a breath stirred, the sky was a dark blue almost to the horizon. The scene was impressive in its solemnity and grandeur. As the Comet rose, the widened extremity of its tail extended past the zenith and seemed to overhan the world. When dawn came, the dark blue of the sky near the point of sunrise began to change into a rich yellow, then gradually came a stronger light, and over the mountain and among the yellow, an ill-defined mass of golden glory rose, in surroundings of indescribable beauty. This was the nucleus of the Comet. A few minutes later, the sun appeared, but the Comet seemed in no way dimmed in brightness, and although in full sunlight the greater part of the tail disappeared, the Comet itself remained throughout the days easily visible to the naked eye; with a tail as long as the Moon is broad.”

Incredible imagining seeing something like that, isn’t it?

Just think. The next Great Comet might be discovered tonight. It might have been discovered LAST night, while you and I were tucked up in bed, and even as you’re reading this blog word of its discovery could be spreading across the internet…

Well, that would be nice, but don’t hold your breath! One day, one day… In the meantime, I hope you found this brief trip back in time in the TARDIS fascinating and it’s not left you too impatient for a truly Great Comet to appear in our sky. The thing is, even if ISON isn’t destined to put on a show like these, that doesn’t matter; that comets like these have been seen in the past at all should fill us all with a sense of wonder, and should actually make us appreciate whatever show ISON puts on for us even more. Comets are common out there, in the great dark. Right now, if it was dark where you live and you had a large telescope you could probably look at a dozen different comets, one after the other. They’d just look like tiny grey puffs of smoke in your eyepiece, but that’s all most comets ever get to look like to us. Just by reaching naked eye visibility Comet ISON will be special, and anything better than that will be a bonus, we have to think of it that way, and not as a Great Comet Lost.

Even if Comet ISON doesn’t go down in history as a Great Comet, we can make it a great comet for the world, in this light-polluted, science-shunning age, by showing it to as many people as possible, and getting across to them just how incredible it is, and how priviliged they are, to be able to see an enormous chunk of filthy cosmic ice, billions of years old, glowing softly in the night sky as it races towards and then around a star, not to return again for a long, long time.