| Discovery | |
|---|---|
| Discovered by: | John Tebbutt |
| Discovery date: | May 13, 1861[1] |
| Alternate designations: | Great Comet of 1861, 1861 II |
| Orbital characteristics A | |
| Epoch: | 2400920.5 (921.0?)[2] |
| Aphelion: | 109 AU |
| Perihelion: | 0.822 AU |
| Semi-major axis: | 55.0 AU |
| Eccentricity: | 0.98507 |
| Orbital period: | 409 yr |
| Inclination: | 85.4° |
| Last perihelion: | June 12, 1861[2] 1500 April 20 (only 5 observations used)[3] 1110 June 4[3] |
| Next perihelion: | 2265[4] |
The Great Comet of 1861 formally designated C/1861 J1 and 1861 II, is a long-period comet that was visible to the naked eye for approximately 3 months.[5] It was categorized as a Great Comet, one of eight in the 19th century.[5]
It was discovered by John Tebbutt of Windsor, New South Wales, Australia, on May 13, 1861, with an apparent magnitude of +4, a month before perihelion (June 12). It was not visible in the northern hemisphere until June 29, but it arrived before word of the comet's discovery.
On June 29, 1861, comet C/1861 J1 passed 11.5 degrees from the Sun.[6] On the following day, June 30, 1861, the comet made its closest approach to the Earth at a distance of 0.1326 AU (19,840,000 km; 12,330,000 mi).[1] During the Earth close approach the comet was estimated to be between magnitude 0[5] and -2[1] with a tail of over 90 degrees.[5] As a result of forward scattering C/1861 J1 even cast shadows at night (Schmidt 1863; Marcus 1997).[7] During the night of 1861 June 30-July 1, the famed comet observer J. F. Julius Schmidt watched in awe as the great comet C/1861 J1 cast shadows on the walls of the Athens Observatory.[7] The comet may have interacted with the Earth in an almost unprecedented way. For two days, when the comet was at its closest, the Earth was actually within the comet's tail, and streams of cometary material converging towards the distant nucleus could be seen.
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.
I. Hasegawa and S. Nakano suggest that this comet is identical with C/1500 H1 that came to perihelion on 1500 April 20 (based on 5 observations).[3]
As of 1992 this Great Comet had traveled more than 100 AU from the Sun, making it even further away than dwarf planet Eris. It will come to aphelion around 2063.