28P/Neujmin

28P/Neujmin, also known as Neujmin 1, is a large periodic comet in the Solar System. With a perihelion distance (closest approach to the Sun) of 1.5 AU (220 million km), this comet does not make close approaches to the Earth.^[1]

28P/Neujmin

Sketch of Comet Neujmin 1 as seen by Edward E. Barnard from the Yerkes Observatory on 9 September 1913.
Discovery
Discovered by	Grigory Neujmin
Discovery date	3 September 1913
Designations
MPC designation	P/1913 R2, P/1931 S1
Alternative designations	Neujmin 1 1913 III, 1931 I, 1948 XIII 1966 VI, 1984 XIX
Orbital characteristics[1][2]
Epoch	17 October 2024 (JD 2460600.5)
Observation arc	110.58 years
Number of observations	1,276
Aphelion	12.38 AU
Perihelion	1.585 AU
Semi-major axis	6.983 AU
Eccentricity	0.77297
Orbital period	18.45 years
Inclination	14.299°
Longitude of ascending node	346.39°
Argument of periapsis	347.47°
Mean anomaly	70.299°
Last perihelion	11 March 2021[3][4]
Next perihelion	23 July 2039[5]
TJupiter	2.168
Earth MOID	0.574 AU
Jupiter MOID	0.960 AU
Physical characteristics[1][6]
Dimensions	21.4 km (13.3 mi)
Synodic rotation period	12.75±0.03 hours
Geometric albedo	0.025
Comet total magnitude (M1)	13.2

Orbital and physical characteristics

The comet nucleus is estimated to be 21.4 km (13.3 mi) in diameter with a low albedo of 0.025.^[1] Since 28P has such a large nucleus, it became brighter than the 20th magnitude in early 2019, roughly 2 years before coming to perihelion. When it came to opposition in May 2020, when it was still 3.5 AU (520 million km) from the Sun, it had an apparent magnitude around 16.9. But during the 2021 perihelion passage the comet was on the opposite side of the Sun as the Earth. The comet is not known for bright outbursts of activity.