It was discovered by Robert George Harrington at Palomar Observatory on 14 August 1953 using the Schmidt telescope. It then had a brightness of magnitude 15. In October 1956 its orbit was affected by the planet Jupiter and on its next return in 1960 the brightness had fallen to magnitude 20. By 1980 it had slightly improved to magnitude 18. It has a period of 7.1 years.
In 1987 and 1994 brightness had significantly increased to magnitude 12. In 1994 Jim Scotti at Kitt Peak Observatory observed that the comet had broken up and that two detached pieces were accompanying the main body, which explained the improvement in the brightness. By 2001 further splitting had occurred.
51P came to opposition on 25 August 2022 when it had a solar elongation of 168 degrees and was 0.73 AU from Earth. It came to perihelion (closest approach to the Sun) on 1 October 2022.[1]
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