The Great Comet of 1861 was discovered by John Tebbutt in Australia on May 13th, 1861.
A “great comet” is one that can not only be seen from Earth, but is also exceptionally bright. Also, it doesn’t refer to the comet in so far as it refers to a particular appearance of a comet. For example, when Halley’s Comet visited the Earth in 1910, it was bright enough to be considered a “great comet”. However, in 1986 it was not bright enough to be considered a “great comet”. The most recent great comet event is McNaught Comet’s close approach in 2007, but the most famous one that happened relatively recently was Hale-Bopp in the 1990s.
While there were several great comets in the 19th Century, the 1861 comet was the most noteworthy. It was one of the brightest comets of all time, outshining all the stars in the sky, just barely excepting the Sun. In addition, the Earth passed so close to the comet that it physically entered its tail for two days. This bright period occurred in late-June/early-July of 1861, but it was at least visible in the sky without a telescope from May to August of that year.
It passed into the northern hemisphere on the 29th of June. On the Fourth of July, a soldier from the Second Wisconsin wrote this about the body:
“We have been visited for a week past by a very large comet which at full day appears very bright and transparent; late at night the tail stretched nearly to the Zenith while the star was near the horizon.” (In other words, it stretched from the nearly very top of the sky to the edge of the horizon. - Jeremy)
The comet soon became a significant sight for the American audience, and in turn it was used in period media referencing the impending Civil War. This is not surprising, as comets – particularly great comets – were seen as harbingers of death and destruction for millennia. In this case, the comet was an accurate predictor of upcoming events, as it was still visible in the sky as troops came up to line near the Bull Run tributary.
It was used, for example, in period political cartoons. One such cartoon was an image of Winfield Scott’s head replacing the icy core of the comet as it cuts through the heavens, with the caption “About This Time You Will Hear Thunder”.
The comet left visibility in August of 1861, and it will not be seen again by the naked eye until the 23rd Century. It is at least 103 astronomical units away from Earth presently, or in other words it is 9.5 billion miles away. It is further away from the sun presently than the classical planet of Pluto.
