C/1861 J1 (Great Comet of 1861)

C/1861 J1 (Great Comet of 1861)

Drawing on 1861 June 30

This drawing was made on 1861 June 30 as the comet passed closest to Earth.

Discovery

John Tebbutt (Windsor, New South Wales) discovered this comet on 1861 May 13.37

Observations

The comet was widely observed in the Southern Hemisphere during June. Although it passed perihelion on June 12, the comet actually continued to brighten and develop a spectacular tail as it continued to approach Earth. Emmanuel Liais (Rio de Janeiro) saw the comet on the 12th and said the nucleus equalled a star of magnitude 2 or 3, while the tail was 40° long. On the 20th Edward John White (Williamstown, Victoria, Australia) said the nucleus equalled a star of magnitude 2 and was distinctly fan-shaped in a telescope. He added that the tail was double, with the western or main tail extending over 40° and the eastern tail extending about 5° and separated by an angle of 34°. The eastern tail was also slightly curved toward the east. The comet's path kept it south of the sun until after June 28, thus making the 29th the absolute earliest Northern Hemisphere observers could have seen it.

Closest Distance to Earth (0.1326 AU):

The comet was well-observed as it passed closest to Earth on June 30. The total brightness was estimated as "not as bright as Jupiter" (fainter than magnitude -2) by Johann Friedrich Julius Schmidt (Athens), while the nuclear magnitude was estimated as 1 by T. Brorsen (Senftenberg), but "intermediate" between Venus and Jupiter according to the Reverend Thomas William Webb (Hardwick Parsonage). He added that the comet had a golden hue to it.

Hermann Goldschmidt (Paris, France) estimated the diameter of the nucleus as near 4", while G. Schweizer (Moscow, Russia) more precisely measured it as 3.07". Webb observed with a 5.5-inch refractor and estimated it as 2", but admitted that he probably underrated it. He added that it was "a fine luminous disc" with "a very ill-terminated, but still definite, limb." Webb also observed the comet at 27x and said the comet looked "as though a number of light, hazy clouds were floating around a miniature full moon." He was describing six "luminous veils" located within the coma, the brightest of which was nearest the nucleus, while the faintest was farthest away. Johann Gottfried Galle (Wroclaw (formerly Breslau), Poland) said the nucleus was "extremely bright and distinct," while the Reverend R. Main (Radcliffe Observatory, Oxford) said a telescope showed it was elliptical, with the major axis "directed nearly towards the Sun." Main added, "A stream of light went off from the upper apparent part of the nucleus, and turned round towards the apparent west in the shape of a sickle. Another but fainter stream was seen on the apparent east side of the first stream, also turning round towards the west."

The coma was described as a parabolic curve by Galle, with Schmidt estimating its diameter as 60-70'. The tail was very impressive and contained a number of rays. Although Galle estimated the length as 30° to 40° and Goldschmidt said it was 35° long and 3° to 4° wide, other observers noted a much longer length. Schmidt said the tail was 120° long, Brorsen estimated it as 90° in length, Webb said it was at least 90° long, and Main indicated it was "considerably longer" than 43°. George Williams (Liverpool) observed a tail ray extending through Boštis into Ursa Major, as well as a somewhat brighter ray extending into Cassiopeia. He suspected they might have been clouds, but noted that both pointed towards the comet's nucleus. Webb and his wife noticed a faint ray "of perfectly similar character to the tail, stretching under the square of Ursa Major, about 3° or 3.5° broad...and traceable about half way from the latter star to Arturus: it pointed to the Comet, but in the twilight no connexion could be made out." Webb added that about 20-minutes later it had become brighter. He concluded it was probably a "cirrus cloud, brought up by the N. W. wind."

July Observations:

Although the comet continued to be well-observed during the first days of July, fewer physical descriptions were being made by July 5th, but these still indicated the tail was of great length. The main tail was estimated as 63 degrees long by Littrow, 85 degrees long by Schmidt, and 45 degrees long by Quirling, with the latter astronomer also indicating the greatest width was 10 degrees. The second tail was estimated as wide and 30 degrees long by Littrow. Schmidt estimated the coma diameter as 50 arcmin. Webb swept rapidly across the tail with his comet eyepiece and noted a slightly darker region extended from the nucleus for a short distance into the tail. Activity was still visible within the coma. Main said the nucleus was "very bright and almost equal to a star of the first magnitude." He added that the two streams of light "now pass symmetrically on each side of the nucleus." Peters said the diameter of the nucleus was 5.7 arcsec or possibly smaller and that the 13.5-inch refractor showed one bright inner envelope and two faint outer ones. In addition, he noted "many fine jets streaming out from the nucleus, part of them recurving to the right, others to the left."

This comet was independently discovered by David Livingston on July 6, who was then traveling down the Shire River near present day Blantyre, Malawi, in Africa. He noted "a large comet in Ursa Major" and estimated the tail length as 23 degrees. Littrow estimated the main tail as 59 degrees long and about 2.5 degrees wide, while the second tail was about 30 degrees long and distinctly fainter since the 5th. Webb said the tail seemed slightly turned to the left again. Peters said, "The secondary tail is quite bright, and as wide as the principal tail, branching off from it to the west under an acute angle." He added that the 13.5-inch refractor revealed a nucleus 3.8 arcsec across.

The last big day of observations for this comet came on July 7. John Kirk, who was traveling independent of Livingston down the Shire River, in Africa wrote, "This night we got sight of a splendid comet in the Great Bear moving rapidly from the sun." Heis said the brightness equalled Gamma Ursae Majoris (magnitude 2.44). Dembowski estimated the tail length as 30 degrees, while Gilliss said it was no more than 25 degrees long and 3 degrees wide. Peters agreed that the tail seemed to have decreased in brightness at its end, but was wider and still visible over 30 degrees. Dembowski said the fan extending from the nucleus was less definite than on the 3rd. Gilliss commented that the luminous sector was "much smaller and fainter, and for the greater part of the time could scarcely be discerned at all as distinct from the general mass of light." Peters said the 13.5-inch refractor indicated the outer envelopes were no longer visible, while the inner envelope seemed to be undulating before his eyes.

Descriptive observations were sparse during the second half of July. On the 16th Heis said the brightness nearly equalled that of Iota Draconis (magnitude 3.29), while Quirling estimated the tail length as 12 to 13 degrees. On the 17th Heis said the brightness was between those of Iota Draconis (magnitude 3.29) and Alpha Draconis (magnitude 3.65). While the comet faded the nucleus was beginning to change as well. E. Schönfeld (Mannheim) said the nucleus appeared a little diffuse on the 18th, while Peters noted on the 24th, "The nucleus now appears much less stellar than before, rather as a blurred surface, of 8" in diameter, though this measure is little reliable." He added that the outline of the envelope was no longer visible, though the moon was nearly full.

Observations for Remainder of 1861:

On August 10, Heis said the comet was three steps fainter than Iota Boötis (magnitude 4.76). On August 12, Peters observed with a 13.5-inch refractor and wrote, "The nucleus has become small and is rather dim...." On August 13, Schönfeld said the coma was 5 arcmin across, and contained a nucleus which was not centrally placed. On August 14, Schšnfeld said the coma was 4 arcmin across. On August 15, Heis said the comet was still a naked eye object.

On September 2, Schönfeld said the coma was 5 arcmin across. On September 3, Schönfeld said the nuclear magnitude was 9. On September 12, Schönfeld said the coma was about 2.5 arcmin across in moonlight. On September 16, Peters said skies were cloudy and affected by moonlight, but he did manage to catch sight of the comet with the 13.5-inch refractor. He noted that the comet's faintness only allowed a faint illumination of the wires used for measuring its position.

On October 1, C. Bruhns (Leipzig) said the comet appeared rather faint in the 6-foot focal length refractor. On October 4, Schönfeld said the nucleus was still visible. Bruhns said the comet appeared rather faint. On October 5, Schönfeld said the nucleus was magnitude 11. On October 11, Peters observed with a 13.5-inch refractor and described the comet as "dull". On October 13, Schönfeld said the coma was round and 2 arcmin across, with a nucleus of magnitude 11. On October 19, Peters observed with the 13.5-inch refractor and noted the nucleus "is more concentrated to a point." On October 25, Schönfeld said the coma was 3 arcmin across, with an eccentrically situated faint nucleus.

On November 4, Schönfeld said the coma was fairly faint, with an indistinct nucleus of about magnitude 11-12. On November 5, Schönfeld said the coma was 1.3 arcmin across. On November 21, Schönfeld said the coma was 1.5 arcmin across. On November 25, Schönfeld said the comet contained a condensation of magnitude 12-13. On November 28, Schönfeld said the diffuse coma was rather faint and 0.7 arcmin across. There was also a weak condensation.

Schönfeld observed on December 22 and 23 and said the comet was fairly bright, with a coma 20 arcsec across, and well condensed. On December 26, Peters observed the comet with a 13.5-inch refractor.

1862:
On January 3, Peters observed the comet with a 13.5-inch refractor. On January 5, Peters observed with a 13.5-inch refractor in moonlight, strong winds, and a temperature of -4ˇ F, and noted the comet was difficult to see. Schmidt observed the comet with difficulty using peripheral vision on both February 3 and 6. O. Struve (Pulkova) saw the comet on April 16 and said the coma was 40" across. He noted, "Its light is, even in its present faint state, not quite uniform, but shows distinctly traces of concentration." The comet was last detected on May 1.

Orbit:

Hopff used three positions obtained between June 30 and July 2, and computed a parabolic orbit which was first published on July 12. The perihelion date was determined as June 11.98. Pape used three positions obtained between June 30 and July 6, and computed a parabolic orbit which was first published on July 12. The perihelion date was determined as June 12.23. Hubbard used three positions obtained between July 3 and 18, and computed a hyperbolic orbit. The perihelion date was determined as June 12.57, and the eccentrcity was 1.0265470.

A. Murmann used three positions obtained between June 30 and July 4, and computed a parabolic orbit which was first published on August 2. The perihelion date was determined as June 12.15. H. Seeling (Altona) used three positions obtained between June 12 and July 21, and computed a parabolic orbit which was first published on August 2. The perihelion date was determined as June 12.21.

Sluzki took positions determined by Schweizer during the period of June 30 to September 10, and computed an elliptical orbit with a perihelion date of June 12.00, and an orbital period of 399.81 years.

During 1880, Heinrich Carl Friedrich Kreutz used 1156 positions obtained between 1861 May 27 and 1862 May 1 and computed an elliptical orbit with a perihelion date of June 12.01 and an orbital period of 409 years. Perturbations for four planets were included.

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