Comet C/1861 J1, the Great Comet of 1861, is discovered

Discovery. John Tebbutt discovered the comet on May 13, 1861, in Windsor, New South Wales, Australia. While searching the western sky, he detected a faint nebulous object near the star Lacaille 1316 in the constellation Eridanus. The comet had an apparent magnitude of +4 at the time of discovery, occurring one month before its perihelion on June 12.

Visibility. The comet was visible to the naked eye for approximately three months. On June 30, 1861, it made its closest approach to Earth at 0.1326 AU. Due to forward scattering, the comet cast shadows at night, as observed by Julius Schmidt at the Athens Observatory. Granville Stuart also noted the comet in western Montana on July 1, 1861.

Classification. C/1861 J1 was categorized as a great comet, one of the eight brightest comets of the 19th century. It was a long-period comet. By the middle of August, it was no longer visible to the naked eye, though it remained visible in telescopes until May 1862. Modern calculations refined its orbital period to approximately 365 years.