11P/Tempel–Swift–LINEAR is a periodic comet roughly 1 km in diameter with a 5.95-year orbit around the Sun. At the perihelion passage on 9 November 2026 the solar elongation will be 170 degrees with a declination of +26. The closest approach to Earth will be two days later on 11 November 2026 at a distance of 0.401 AU (60.0 million km). The comet may brighten enough in late 2026 to get into the reach of smart telescopes.
Observational history
Discovery In 1869, the comet's perihelion was around 1.063 AU (159.0 million km) from the Sun. Ernst Wilhelm Leberecht Tempel originally discovered the comet on 27 November 1869, from his observatory at Marseille. It was later observed by Lewis Swift from the Warner Observatory on 11 October 1880, and he realised that it is the same comet as Tempel's.
Loss and recovery After 1908, the comet became an unobservable lost comet due to a series of four close flybys of Jupiter between 1911 and 1946 perturbing its orbit significantly enough that made subsequent apparitions of the comet unfavorable for observations in decades. Nevertheless, Brian G. Marsden computed the resulting orbit based on the observations between 1891 and 1908, and predicted a favorable return in 1963, however the comet remained unobserved. Despite this, additional predictions of the comet's favorable returns were later attempted by Marsden and Zdenek Sekanina in 1971, and Shuichi Nakano in 1995. On 7 December 2001, an object designated as P/2001 X3 was found by the Lincoln Near-Earth Asteroid Research (LINEAR) program. Analysis of images taken between 10 September and 17 October 2001 later confirmed that P/2001 X3 was the recovery of the previously lost comet Tempel–Swift.
Recent observations The comet was not observed during the 2008 unfavorable apparition because the perihelion passage occurred when the comet was on the far side of the Sun. The comet was observed during the 2014 and 2020 apparitions. For the 2026 perihelion passage, the comet was recovered on 6 August 2026. The comet will next come to perihelion on 9 November 2026, then two days later on the 11th, make a closest approach to Earth of 0.4012 AU (60.02 million km).
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References
External links 11P/Tempel–Swift–LINEAR at the JPL Small-Body Database 11P/Tempel–Swift–LINEAR at Gary W. Kronk's Cometography 11P/Tempel–Swift–LINEAR at Seiichi Yoshida's website 11P/Tempel–Swift–LINEAR at Gideon van Buitenen's website