64P/Swift–Gehrels

For other comets discovered by Lewis A. Swift, see Comet Swift.

64P/Swift–Gehrels is a periodic comet in the Solar System which has a current orbital period of 9.23 years.

64P/Swift-Gehrels

Comet Swift–Gehrels photographed by Alexander Vasenin from Moscow, Russia on 11 October 2018
Discovery
Discovered by	Lewis A. Swift Tom Gehrels
Discovery date	17 November 1889 8 February 1973
Designations
MPC designation	P/1889 W1 P/1973 C1
Alternative designations	Swift 1 1889f, 1973d, 1981j, 1991c 1889 VI, 1972 VII, 1981 XIX, 1991 II[1]
Orbital characteristics[2]
Epoch	9 December 2017 (JD 2458096.5)
Observation arc	6,707 days (18.36 years)
Number of observations	3,436
Aphelion	7.518 AU
Perihelion	1.393 AU
Semi-major axis	4.456 AU
Eccentricity	0.687
Orbital period	9.407 years
Inclination	8.948°
Longitude of ascending node	300.00°
Argument of periapsis	97.144°
Last perihelion	3 November 2018
Next perihelion	31 March 2028[3]
TJupiter	2.496
Earth MOID	0.4401 AU
Jupiter MOID	0.6491 AU
Physical characteristics[2]
Dimensions	3.2 km (2.0 mi)
Comet total magnitude (M1)	14.5
Apparent magnitude	9.0 (2018 apparition)

Observational history

It was originally discovered on 17 November 1889 by Lewis A. Swift at the Warner Observatory, Rochester, New York, and was described by Swift as being pretty faint. It was rediscovered after it became a lost comet on 8 February 1973 by Tom Gehrels at the Palomar Observatory, California who estimated its brightness as a very low magnitude 19.^[4]

It was also observed in 1981, 1991, 2000, 2009 and 2018. The 2018 apparition was the most favourable, with the comet reaching a peak magnitude of 9. It had its closest approach to the Earth on 28 October 2018, at a distance of 0.445 au.^[5] The comet had four outbursts. The brightest was on 14 August, during which the comet brightened 2.7 magnitudes.^[6]

See also

• List of numbered comets