Header 1843

Comet 1843
The tail of the 1843 comet, as seen from Blackheath, March 17. (Illustrated London News)

Friday, March 17, 1843. From Blackheath, near London, the Sun set behind a layer of smoke over the capital. As the twilight faded, west by south, a vast shaft of light rose up from the horizon, radiating apparently from the sunken Sun. An anonymous observer drew a picture of the phenomenon ’on the spot', (later published by the Illustrated London News). He wondered if it could be the tail of a huge comet, although he later concluded that he was looking at the Zodiacal Light, especially when it disappeared from view at about 9.30 p.m.
Another journal claimed that the comet illustration was a 'second-hand' one, prepared for a different occasion, and when the artist claimed to have seen the appearance, the Greenwich Observatory astronomers were unable to discern it. The Illustrated London News replied that the object had been seen on that night by Sir John Herschel and other eminent observers, and the accuracy of the sketch had been confirmed by several 'anonymous and disinterested sources'.

There was some dispute as to whether this mysterious beam was actually a comet or the Zodiacal Light, which appears as a faint pyramidal luminosity above the western horizon in spring and the eastern in autumn. An astronomer of Bruges had no doubt that the phenomenon was the zodiacal light. At Cheltenham, some persons at first took it for a lunar rainbow. However, Sir John Herschel, Sir James South and other astronomers had no doubt that 'the brilliant light' was the tail of a comet. Herschel announced that a comet 'of enormous magnitude' was passing through the solar system, and was not far from perihelion.

A few days earlier, on March 6, Lieutenant M. F. Maury, of the Hydrographic Office in Washington, had read a newspaper paragraph stating that a comet was visible with the naked eye near the Sun. The clear daylight sky was scanned, but nothing was seen either with the naked eye or a telescope, nor was anything visible just after sunset. The astronomers retired, until the officer of the watch announced that the comet had appeared in the west. "The phenomenon was sublime and beautiful. The (magnetic) needle was greatly agitated, and a strongly marked pencil of light was streaming up from the path of the Sun in an oblique direction...". The edges of this beam of light were parallel; it was 1 degree 30 minutes broad and 30 degrees long.

On March 7, the clear daytime sky within 15 degrees of the Sun was telescopically surveyed. Nothing was seen except a spot on the Sun itself. As sunset still lingered on the horizon, the first stars appeared. At that moment, "a well-defined pencil of hairy light was seen pointing toward the sun." At 6 hours 19 minutes (sidereal time), the streamer of light was 55 degrees long and 1 degree 45 minutes wide; assuming the head was close to the Sun, it must, judging by the angle it made with the horizon, have been at least 65 degrees in length. For some reason, the streamer then began to fade and soon completely disappeared.

Next day, March 8, telescopes were turned to the Sun, where the sunspot was suspected of being the nucleus of the comet in transit, but overcast skies for the next two days prevented the astronomers from detecting any unusual motion the spot might have. However, on March 8, the sky after sunset became clear, and "was watched with eager but confident expectation of again seeing the same beautiful phenomenon, which had excited our admiration and wonder for the two evenings previous." Surely enough, at 5 hours 54 minutes, a streak of light was dimly seen. Twenty minutes later, it was distinctly visible as a faint nebulous arch, 85 degrees long, spanning the south-western sky, with the terminus of the beam far below the horizon. About thirty minutes later, the sky clouded over.

On March 11, the weather cleared, and the Sun was examined for the spot which might have been the nucleus of the comet. However, it had disappeared.
Maury had little doubt that the 'strange light', despite contrary opinions, had been the tail of a great comet, and that "it may be classed among the most remarkable that have ever appeared."
To confirm this, a correspondent of the
U.S. Gazette said he had seen the nucleus of the comet. Viewed through a 9-foot refractor, the nucleus appeared, not as a well-defined disc, but a 'faint cloud', condensed in the centre and with a diffuse border.

On the evening of March 13, from New Haven, the nucleus of the comet was also visible, 'considerably elevated above the horizon'. The tail, which resembled 'a very large feather', was about 40 degrees long, and took over two hours to set, although, thanks to the Moon and a misty horizon, "its feeble light was extinguished rapidly".

The great comet of 1843 had actually first appeared in the southern hemisphere, and by the time it reached northern skies, 'its splendour had much diminished'. General J.A. Ewart, at sea near St. Helena, reported that at first a small part of the tail was visible, at right angles to the horizon; night after night it grew larger, "until at last up came the head...It was a grand and wonderful sight, for the comet now extended (over) one-third of the heavens, the nucleus being...about the size of the planet Venus." On February 28, the comet was seen in full daylight near the Sun, and during the first week in March, 'it presented a most splendid appearance' in the southern hemisphere,

The Royal Mail Company's steamer
Tay, which left Jamaica on February 14th, arrived at Falmouth on Sunday, March 19th. On her voyage home, beginning on March 6th, an 'extraordinary phenomenon' had been seen on several days after sunset. It resembled a 'bright sunbeam' with parallel sides, rising to an altitude of 32 degrees above the horizon. From Brazil, the tail seemed of a 'brilliant silver colour", with a streak of bright gold running through from the nucleus.

Comet 1843 02
The comet as seen from the William Fulcher, March 4
(Illustrated London News)

On March 3, the captain of the brig
William Fulcher, becalmed at 14º 30' N., 36º 30' W., observed "a shower of rockets and Aurora Borealis". On March 4, in the same direction, he saw "what proved to be the comet".

The comet had passed perihelion on February 27. At the moment of closest approach, just before 10 p.m., it was within 81,500 miles of the Sun's surface, moving at 348 miles a second. Between February 27 and 28 it described an arc of 292 degrees. The heat to which the comet was exposed near perihelion "must have been enormously greater than the heat which can be raised in our mightiest furnaces."

The comet was lost to view in April, so the opportunities for observation were limited. The calculated orbit 'could not be certainly distinguished from a parabola', so it evidently would not return for centuries, if at all. However, in 1880 and 1882, comets were seen moving in almost the same orbit. "These comets may have been part of some mass which gradually broke up." It was suggested that the parent could have been a great comet seen in the year 1106. The astronomer J.R. Hind said, however, that the 1843 comet 'could not possibly be the same' as the comet of 1106, which was seen for some time in the northern sky. The 1843 comet could only remain about three hours north of the ecliptic.

An engraving of the great comet of 1843, probably featuring artistic license

As the Great March Comet of 1843 performed its hairpin turn round the Sun and retreated into the depths of space, there were speculations as to the possibility of a comet colliding with the Earth. "The effect...of such collision might be very disastrous; but the real probability is that the Earth would bear off in the upper regions of her atmosphere the diffused matter of many comets without...disturbing the composure of us poor mortals in these nether parts." As further reassurance, the French astronomer Arago had calculated that the chances of collision were 280,000,000 to 1 against. There were other opinions, from some who believed that the destruction of the Earth by a comet was 'indeed, a well-sustained probability.' They pointed to the asteroids, which Herschel had determined to be angular masses, and therefore 'fragments of a shattered world', which was probably the result of 'a concussion with a comet'.