99P/Kowal

99P/Kowal, also known as Kowal 1, is a periodic comet in the Solar System that orbits out by Jupiter and has a 15 year orbital period. It has been observed regularly since 2019. Its most recent perihelion occurred in April 2022, and is expected to return by May 2037.^[3]

99P/Kowal

Discovery[1]
Discovered by	Charles T. Kowal
Discovery site	Palomar Observatory
Discovery date	24 April 1977
Designations
MPC designation	P/1977 H2 P/1991 D2
Alternative designations	Kowal 1 1977 III, 1992 VI 1977f, 1991i
Orbital characteristics[2][3]
Epoch	17 October 2024 (JD 2460600.5)
Observation arc	47.25 years
Number of observations	1,740
Aphelion	7.489 AU
Perihelion	4.702 AU
Semi-major axis	6.095 AU
Eccentricity	0.22857
Orbital period	15.049 years
Inclination	4.339°
Longitude of ascending node	28.083°
Argument of periapsis	174.59°
Mean anomaly	60.356°
Last perihelion	12 April 2022
Next perihelion	6 May 2037[4]
TJupiter	2.956
Earth MOID	3.724 AU
Jupiter MOID	0.307 AU
Physical characteristics[2]
Mean diameter	10.2 km (6.3 mi)
Comet total magnitude (M1)	6.7
Comet nuclear magnitude (M2)	11.5

Observational history

Charles T. Kowal discovered this comet shortly after reporting the discovery of asteroid 2063 Bacchus (then known as 1977 HB) on the night of 24 April 1977.^[1] It already passed perihelion when it was first spotted as a 16th-magnitude object within the constellation Virgo.^[5] Orbital calculations by Shuichi Nakano and Brian G. Marsden predicted that the comet has a 15-year orbit around the Sun, and was expected to return by 1992.^[5] It was successfully recovered by James V. Scotti from the Kitt Peak Observatory's Spacewatch program on 21 February 1991.^[6]

Between 12 and 14 May 2021, a small outburst temporarily brightened Comet Kowal 1, which raised its apparent magnitude from 18.32 to 17.6.^[7]