109P/Swift-Tuttle

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**109P/Swift-Tuttle**
Discovery
Discovered by:	Lewis Swift Horace Parnell Tuttle
Discovery date:	July 16, 1862
Alternate designations:	1737 N1; 1737 II; 1862 O1; 1862 III; 1992 S2; 1992 XXVIII
Orbital characteristics ^A
Epoch:	October 10, 1995 (JD 2450000.5)
Aphelion distance:	51.225 AU
Perihelion distance:	0.9595 AU
Semi-major axis:	26.092 AU
Eccentricity:	0.9632
Orbital period:	133.28 a
Inclination:	113.45°
Last perihelion:	December 11, 1992
Next perihelion:	July 12, 2126

Comet Swift-Tuttle (formally designated as 109P/Swift-Tuttle) was independently discovered by Lewis Swift on July 16, 1862 and by Horace Parnell Tuttle on July 19, 1862.

The comet made a return appearance in 1992, when it was rediscovered by Japanese astronomer Tsuruhiko Kiuchi.

It is the parent body of the Perseid meteor shower, perhaps the best known shower and also among the most reliable in performance.

The comet is on an orbit which will almost certainly eventually hit either the Earth or the Moon, though not within this millennium.^[1] Upon its 1992 rediscovery, the comet's date of perihelion passage was off from the then-current prediction by 17 days. It was then noticed that, if its next perihelion passage (August 14, 2126) was also off by another 15 days, the comet would very likely strike the Earth or Moon. However, the orbit was improved by the identification of earlier passages, dating as far back as 69 BC, and the new orbit's stability turned out to be greater than expected, making the threat disappear.^[2]