A total solar eclipse, such as that which will be crossing America on 21 Aug 2017, would present a great opportunity to discover a bright comet near the Sun. Has that ever happened? The answer is yes.
A comet, perhaps magnitude -4 or brighter, was spotted about 1.4° SW of the Sun during the total solar eclipse of 1 Nov 1948. The editors of Sky & Telescope write in the January 1949 issue, “British Astronomical Association Circular No. 303, dated November 10, 1948, under the title, ‘The Eclipse Comet, 1948 I,’ reads in part:
There can be little doubt that the bright comet now reported seen in the southern morning sky is identical with the one seen during the eclipse of November 1. The Times of November 2 in the report of the eclipse from its correspondent at Nairobi stated that a bright comet, with a long tail, was seen both by the crew of an R.A.F. aircraft and by observers on the ground. The head, it was stated by one amateur astronomer, was still visible a few seconds after the Sun began to emerge.
A cable received by Dr. R. d’E. Atkinson, leading the Royal Observatory expedition, reports photographic confirmation of it, saying it was 93′ from the centre of the Sun in position angle 226°, and was very bright, with a tail.
“Harvard Announcement Card 956, dated November 22nd, reads in part:
Dr. Leland E. Cunningham, Students’ Observatory, University of California, Berkeley, writes: ‘New elements have been determined for the bright comet . . . . These place the comet in position angle 228° and 104′ distant from the sun at the time of the total solar eclipse on November 1, which are in moderate agreement with Atkinson’s observed values of 226° and 93′, respectively.’
“Thus, although Comet 1948 I was missed by northern observers before it passed perihelion late in October, when its tail must have extended into the evening sky after sunset, the total eclipse of the sun provided a favorable opportunity to observe the comet practically a week before southern observers viewed it in their morning sky. It well can be called the ‘eclipse comet’ of 1948.”
The editors of Sky & Telescope write in the March 1949 issue, “From The Observatory of December, 1948, we quote part of the proceedings of the meeting of the Royal Astronomical Society held on November 12th, at which Dr. R. d.’E Atkinson told something of his recent eclipse expedition to East Africa, and the discovery of the comet during the eclipse. Dr. Atkinson said:
I propose to speak mainly about the comet which was observed during the eclipse; as far as our own eclipse observations are concerned, I believe they were successful, but the films have not yet been developed.
The comet, though very bright, was not visible at Mombasa, where we were (98% totality), but several newspaper reports from further north referred to it; they did not sound very convincing. A photograph was published, but as printed it did not actually show the comet; the accompanying description was also based on an error, as I later learnt. On the journey to Nairobi, sixty hours after the eclipse, I spoke to an eyewitness, whose account disagreed with that in the paper. It was not until I had seen the photographs taken by the R.A.F. at Nairobi, and had found that they agreed with eye-witness reports at both places, that I realised it must have been a comet; I then made a very rough measurement of its place on the R.A.F. film, and telegraphed Dr. Merton. As a result of my interest in these photographs, which were taken at 13,000 feet just within and just outside the shadow, the Air Commodore very kindly let me bring the films home for thorough examination. [On one picture] very much enlarged from a hand-camera snapshot also taken by a member of the crew . . . the tail is clearly visible; visual observers all agreed that it extended downwards until it reached either clouds or the horizon, and it must have been twenty degrees long at least. The visible part of it does not point away from the Sun at all; any portion which does this must have been extremely foreshortened. [On another picture] the scale is larger and the definition much better, but the tail is too much underexposed to show except with a magnifying glass. Viewed in this way, and accepting the idea that the root of the tail will point away from the Sun, one can see enough indications of curvature to make it seem that it is convex to the west; I therefore concluded in my cable a guess that the motion would be westwards, and this has proved correct. The comet must certainly have been very bright; these pictures were taken with an aperture of f/5.6 and an exposure of 1/300 second; moreover, the head was visible for some 5-10 seconds after the end of totality. It must certainly have been brighter than Venus. I have now measured up three separate negatives, and they agree closely in giving a distance from the centre of the Sun of 105.4 minutes, and a position angle of 230°; however, there is some possibility of systematic error, and I have written to the Air Commodore to ask for further details. If systematic errors can be eliminated, the place should, I think, be useful for orbit determination; it is a week earlier than any other place.”
Thus writes British astronomer Robert d’Escourt Atkinson (1898-1982) about comet C/1948 V1, the “Eclipse Comet of 1948” seen at Nairobi and Mombasa, Kenya on 1 Nov 1948. It was next observed in the morning sky on 8 Nov 1948, and continued to be followed until 3 Apr 1949.
According to Edward S. Holden (1846-1914), John Martin Schaeberle (1853-1924) discovered a comet-like object on photographic plates taken during the 16 Apr 1893 total solar eclipse, but it has since been determined (Cliver 1989) that this was a coronal mass ejection (CME).
German-born British physicist Arthur Schuster (1851-1934) recorded a comet on photographic plates of the total solar eclipse of 17 May 1882 in Egypt. The comet moved noticeably during the 1m50s of totality. It is thought that this comet was a member of the Kreutz sungrazer group of comets. It has received the designation of X/1882 K1. The “X/” indicates that there were not enough observations of this comet to determine an orbit. In fact, the only observations of this comet were during the total solar eclipse. The comet is sometime called Comet Tewfik—named after the ruler of Egypt at that time in recognition of his hospitality towards the eclipse party.
A comet was discovered during the eclipse of 19 Jul 418 at Constantinople (Istanbul, Turkey) and was observed for four months afterwards.
Seneca the Younger (c. 4 BC – AD 65) writes in his Naturales quaestiones (Natural Questions):
Posidonius, in fact, tells us that during an eclipse of the Sun a comet once appeared which the sun’s proximity had hitherto concealed.
Did Posidonius (c. 135 BC – 51 BC) see this comet, or was he referring to an even earlier observation made by someone else? With so much of the knowledge of the ancient world lost or destroyed by barbarians and zealots, we may never know.
Clarke, J. 1910, Physical science in the time of Nero; being a translation of the Quaestiones naturales of Seneca
Cliver, E. W. 1989, Solar Physics, 122:2, 319-333
Federer, C. A. Jr., Sky & Telescope, January 1949, pp. 59-60
Federer, C. A. Jr., Sky & Telescope, March 1949, p. 110, 113
Hetherington, B. 1996, A Chronicle of Pre-Telescopic Astronomy
Kronk, G. W., Cometography, X/1882 K1 (Eclipse Comet or “Tewfik”)
Poitevin, P., Eclipse Comets
Seneca c. 65 AD, Naturales quaestiones, 7.20.4
Vaquero, J. M. 2014, Physics Today, 67:5, 9
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Incidentally, for those of you in or near Dodgeville, Wisconsin, the nearest city you can drive to that puts you close to the eclipse centerline (where totality will last the longest) on August 21, 2017, is Columbia, Missouri. Travel time will be around 6 hours.