An impression of the great comet of 1861 as seen from Kent on the evening of June 30th. The Earth is believed to have passed through the comet’s tail on this day.
Panting © Chris Chatfield.
The twentieth century was almost devoid of great comets, thus disproving the notion that they are portents of war and disaster. The nineteenth century was, however, amply supplied. Victorian cometophiles could debate the relative spectacles provided by the visitors of 1843, 1858, 1861 and 1882, while sipping the last of the 'comet wine', a famous vintage from Portugal produced while the great comet of 1811 was visible.
The comet of 1861 was not the most spectacular of the nineteenth century (that probably being the comet of 1843) or the most beautiful, which was Donati's of 1858, but its appearance was dramatic, and it interacted with the Earth in an almost unprecedented way. For a while the Earth was actually within the comet's tail, and the inhabitants of this planet had a brief but giddy view of streams of cometary material converging towards the distant nucleus. By day also the Sun was dimmed as the Earth ploughed through the comet's gas and dust.
John Tebbutt, a sheep farmer and amateur astronomer of Windsor, New South Wales, Australia, discovered the comet of 1861 on May 13. It was magnitude 4, visible to the naked eye, and a month before perihelion (June 11). Before news of the discovery could reach the northern hemisphere, the comet itself appeared in northern skies.
The first person in England to see it may have been William C. Burder, of Clifton, Bristol, who dashed off a letter to the Times on Sunday, June 30th. "Sir - At 2.40 a.m. today I detected a brilliant comet near the north-west horizon. It was visible till 3.20 a.m….it appeared as bright as Capella and was favourably situated for the comparison. It was surrounded by a nebulous haze, but I saw no tail…The daylight put out the both the comet and Capella nearly at the same time; your readers will therefore consider this a proof that it is a brilliant object." (A resident of Hawkhurst, in Kent, claimed to have seen it on the evening of June 29, and to have mistaken it for the rising Moon).
As the long midsummer Sunday drew to a close, there was noticed a strange appearance in the sky. E. J. Lowe, at Beaston, said, "The sky had a yellow, auroral, glare-like look, and the sun, though shining, gave but a feeble light…in our parish church the vicar had the pulpit candles lighted at seven o'clock, a proof that a sensation of darkness was felt even with the sun shining." J. R. Hind, in London, told the Times; "there was a peculiar phosphorescence or illumination of the sky, which I attributed at the time to an auroral glare; it was remarked by other persons as something unusual".
Even before the sun set, the comet became visible. E. J. Lowe saw it first at 7.49 p.m. (GMT), when it had no tail, and looked like "Jupiter in a fog, only much larger." By 9 p.m. the tail was visible, and by 10.30 it was 45° long, rising vertically and spreading out until it was three times the diameter of the Moon. John Hippisley, at Ston Easton in Wiltshire, saw the comet at 10 p.m., when it was conspicuous despite strong twilight.
Midsummer nights are never quite dark even in southern England, but on the night of June 30th the comet was bright enough to cast a shadow on white paper, despite the fact that the nucleus was only a few degrees above the horizon. Hippisley said the tail was curvilinear, passing across the Pole Star, and sweeping deep into the constellation Lyra. It was at least 90° long.
A drawing by the English observer G. Williams showed the comet with its nucleus near Capella and having an enormous fan-shaped tail reaching up to Polaris, with subsidiary jets streaming down from Ursa Major and Cassiopeia, like converging railway lines.
Some disputed the accuracy of this picture, but on July 6, J. R. Hind told the Times, "Allow me to draw attention to a circumstance relating to the present comet…It appears not only possible, but even probable, that in the course of Sunday last, the earth passed through the tail at a distance of perhaps two-thirds of its length from the nucleus".
On June 28, at 6 pm, the nucleus of the comet was in the ecliptic, about 13 million miles from the Earth. Had the tail streamed directly behind the comet, the Earth would have encountered it soon after 10 p.m. on June 30th. But tails always lag behind the nucleus, and Hind, judging by the amount of tail curvature and the comet's direction of motion, estimated that the Earth would have entered the tail in the early morning of June 30; "or, at any rate, it was certainly in a region which had been swept over by cometary matter a short time previously."
On July 1, the comet was not visible until 8.45 p.m., an hour later than on the previous night. The nucleus was also much less hazy, no longer being seen through a screen of tail material. Between July 2 and July 19, telescopic observations of the head of the comet showed a total of 11 luminous envelopes rising successively from the nucleus. A new one was emitted every two days.
The comet was withdrawing from the Earth at the rate of about 6 million miles a day; on July 12th it was 37,800,000 miles away, on July 28th 78,900,000 miles. As it did so, the full length of its vast tail could be seen. Secchi claimed that on July 1 and 2 it was 118° long.
By the middle of August the comet was no longer visible to the naked eye, but it was visible in telescopes until May 1862. An elliptical orbit with a period of about 400 years was calculated, which would indicate a previous appearance about the middle of the 15th century, and a return in the 23rd century.
THE COMET OF 1861
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