10P/Tempel, also known as Tempel 2, is a periodic Jupiter-family comet with a 5 year orbital period. It was discovered on July 4, 1873 by Wilhelm Tempel. The comet nucleus is estimated to be roughly the size of Halley's Comet at 10.6 kilometers in diameter with a low albedo of 0.022. The nucleus is dark because hydrocarbons on the surface have been converted to a dark, tar like substance by solar ultraviolet radiation. The nucleus is large enough that even near aphelion (furthest distance from the Sun which is near the orbit of Jupiter) the comet remains brighter than magnitude 21. This image was taken on the night of August 9th 2010 when the brightness of the comet was about magnitude 8.6. The most favorable apparition of 10P/Tempel 2 was in 1925 when it came within 0.35 AU (52 million km; 33 million mi) of Earth with an apparent magnitude of 6.5. The next perihelion passage will be on March 24th 2021 when the comet will have a solar elongation of 30 degrees at approximately apparent magnitude 11. On August 3, 2026, comet Tempel 2 will have another close pass within about 0.41 AU (61 million km; 38 million mi) of Earth and its apparent magnitude is expected to be 6.1.