by Duncan Lunan

I came across this book a week ago in ArCaS, the major charity shop on Arran, and it’s a treasure trove.  It was one of a number of popular science books published that year in anticipation of Kohoutek’s Comet, which was detected unusually far from the Sun, and expected to become spectacular in January 1974.  In the event it produced large volumes of dust and never brightened as hoped  (Fig. 1), though the scientific return from it was considerable  (George W. Harper, ‘Kohoutek, a Failure that Wasn’t, Analog, July 1974).  The weather that month was terrible and the Glasgow Herald said there had been no observations of it in Scotland, but there were at least two.  Robert Law saw it in the west from the Coats Observatory in Paisley, through a brief break in the clouds, and I had the same experience, possibly under the same break, with my 3-inch refractor in Troon.

There was a bigger outpouring of such books before the return of Halley’s Comet in 1985-86, and one of the best was Comet, by Carl Sagan and Ann Druyan  (Guild Publishing, 1985, Fig. 2), which had a lot of information on historical comets, as did a compilation of papers from the archives of Scientific American  (J.C. Brandt, ed., Comets, W.H. Freeman, San Francisco, 1981).  Some years later I acquired a copy of the 2-volume Popular Astronomy by Francois Arago  (Admiral W.H. Smyth, Robert Grant, eds., Longman, Brown, Green, Longmans and Roberts, 1858), which listed many of the historical comets tabulated by Edmond Halley and others, inspired by the visit of Halley’s Comet in 1662.  Arago’s interest was mainly in their orbits, and in many cases he gave only the dates, taking for granted that they were posigrade, in the general direction of movement in the Solar System, or mentioning that they were retrograde like Halley’s.  He also noted whether they had passed close to the Earth or the Sun, but usually gave little other detail.

What first attracted me to the Ash and Grant Comets was the photographs, all in black and white, of comets I remembered from my youth – Arend-Roland  (1957 – Fig. 3), the first comet I saw, Ikeya-Seki, for which I searched in vain in the summer twilight of 1965  (Fig. 4), but sadly not Comet Bennett  (Fig. 5), which I observed with the same 3-inch in 1970, and which inspired my most successful short story to date, ‘The Comet, the Cairn and the Capsule’  (see ‘My SF, ON, 10^th September 2023 ).  But when I got into the text, what was particularly valuable was the details given of many of the historical events.  In particular, towards the end there’s a two-page list of historical comets, starting with one seen by Aristotle in 371 BC and coming up to Kohoutek’s, giving colours, the sizes of the nuclei and the sizes and shapes of the tails, along with shortened comments by contemporary observers.  All this complements a listing of mediaeval astronomical, meteorological and geological events, and others, begun by Mrs. Jane Greatorex of Essex and kindly shared with me when I was researching Children from the Sky  (see ON, June 19^th and 26^th, 2022 ).  My late colleague Jamie Bentley called its expanded version ‘Brother Lunan’s Book of Wonders’ and it’s probably now too big for publication, as well as needing substantial research to close the gaps, but it’s very useful for looking up what else was happening at the time of historical events.

Comets then goes on to provide a detailed listing of all the historical appearances of Halley’s Comet.  Isaac Asimov gave a short list in one of his articles  (‘Change of Time and State’, Fantasy & Science Fiction, April 1982, reprinted in X Stands for Unknown, Doubleday, 1985, Fig. 6), and I duly mined it out, but his main point was to disprove the assertion that comets were unlucky, that one in particular, by listing dates on which no major disasters occurred.  A complete list is useful, and the great thing is, once it’s done, it’s done.  What’s remarkable is how different the comet has looked at different times.  The Chinese described it as blue in 141 AD, as it appeared in 1910  (colour reconstruction, Fig. 7).  Note the triple star images as the telescope tracks the comet, differently coloured because the filters had been changed.  But in 1222 it was described as ‘very red’, not mentioned here, to say nothing of how Giotto di Bendone painted it as the Star of Bethlehem in 1304  (Fig. 8), after its passage in 1302, because Ash and Grant don’t mention that either.  The changes in colour presumably relate to different amounts of dust released.

Though not specifically on comets, there was a surge of books in the latter half of the 19^th century which gave similar space to details of Comet Swift-Tuttle, the Great Comet of 1862.  It’s the parent comet of the Perseid meteors in August  (Fig. 9), and in 1982 there was a serious prospect that it might strike the Earth, because 19^th century observers estimated its period at 120 years. 

Computer analysis of the 1862 results indicated that there were seven active areas on the nucleus, creating jets which could act as rockets and move it in any direction  (Sagan and Druyan, op cit.)  David Langford commissioned me to write an article which he accepted for the fifth issue of the British SF magazine Extro, which sadly ceased with Issue # 4 after a serious breach of contract by the distributors.  In 1986 I entered an expanded version for the annual Griffith Observer/Hughes Aircraft essay content, featuring Gordon Ross’s idea for deflecting comets using parabolic solar sails  (Fig. 10), but it wasn’t placed.  Gordon and I published two letters about it in Space Policy, the first public appearance of the idea as far as we know, and eventually I placed the expanded article with its original title of Keep Watching the Skies!, quoting the ending of The Thing from Outer Space, in the October 1994 issue of Analog, with a painting by Sydney Jordan  (Fig. 11), based on a 19^th century lantern slide supplied by the late John Braithwaite.  Still later the Swift-Tuttle section formed the first half of the opening chapter of my Incoming Asteroid!  What Could We Do About It?  (Springer, 2013), where I explained why the rest of the book was devoted to asteroids.  Having described the results of space probe mission to comets since International Comet Explorer and the Giotto encounter with Halley’s Comet, both in 1986, my point was that if the secret of successful defence is ‘Know Your Enemy!’, the problem with comets was that no two were alike.  The varying details in the Comets lists give that point emphasis and historical depth,

The 1982 concern about Comet Swift-Tuttle was misplaced, but not by all that much.  Some 19^th century observers had estimated the period at an alternative 130 years, and that proved to be correct when the comet returned in 1992  (Fig. 12). 

It was nowhere neat the Earth that time, but it would pass very close in 2126 and 2261.  And the comet’s nucleus proved to be much larger than expected, 26 miles in diameter – nearly three times the size of the Chicxulub impactor 65 million years ago, which wiped out 90% of species on Earth.  Arthur C. Clarke ended his novel The Hammer of God  (Gollancz, 1993, Fig. 13)  with a warning about it, and the late Dr. Arthur Hodkin pointed out that only Star Trek technology, like warp drives and tractor beams, would be capable of shifting it.  The good news, such as it was, was that with that amount of inertia, the jets were unlikely to move it from the near-misses predicted by Robert McNaught of Prestwick, now at the Anglo-Australian Telescope.  Nevertheless, out there, half way round its orbit, Arthur said that it had plenty of time to change its mind.  And as Patrick Moore was fond of saying, comets are like cats:  they have tails, and no-one knows what they’ll do next.

That provides a link to note the passing of Millie, beloved family pet of my friend Ashley Bostel.  Millie’s last journey to the vet this month was at the age of 24, extraordinary for a cat.  As it happens, Vega, the brightest star of the Summer Triangle, is now overhead o’nights and is 25 light-years away.  In several article I’ve mentioned my friend Dr Gerry Nordley’s concept of a mini-Dyson sphere, which could be used as a phased optical array to study planets at interstellar distances with a resolution of under half a metre  (Fig. 14).  If astronomers at Vega have been building one in the last 25 years, we won’t know it yet because the diminution of the star’s light has still to reach us.  If they have one and it’s operational now, in a year’s time those astronomers will be able to say, “I just love the things which that kitten gets up to”.