| 28P/Neujmin | |
| Discoverer: | Grigory Nikolaevich Neujmin |
| Discovery Date: | September 3, 1913 |
| Designations: | 1913 III; 1931 I; 1948 XIII; 1966 VI; 1984 XIX |
| Epoch: | March 6, 2006 |
| Semimajor: | 6.911 AU |
| Perihelion: | 1.551 AU |
| Aphelion: | 12.27 AU |
| Eccentricity: | 0.7755 |
| Period: | 18.17 yr |
| Inclination: | 14.2514° |
| Earth Moid: | 0.55abbr=unitNaNabbr=unit |
| Last P: | March 11, 2021[1] [2] December 27, 2002 |
| Next P: | 2039-Jul-23 |
| Dimensions: | 21.4 km |
| Rotation: | 12.75 ± 0.03 hours[3] |
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 1.5AU, this comet does not make close approaches to the Earth.
The comet nucleus is estimated to be 21.4 kilometers in diameter with a low albedo of 0.025. 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 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.