A Partial Disintegration of Active Centaur/Comet P/2020 MK4?

Abstract Centaur P/2020 MK4 (a = 6.19 au, e = 0.011) was discovered in 2020 and quickly brightened to V ∼ 18.5. As of early 2022 November, no astrometric observations had been reported in 2021 or 2022. The object should have been easily found had it retained its 2020 absolute magnitude. We find that P/2020 MK4 now appears as an ∼10″ wide low surface brightness coma, with a faint (r ∼ 24.9) point-like source. The rates of brightening and fading of P/2020 MK4 are both much slower than the larger Centaur 29P/Schwassmann-Wachmann 1, which is on a similar orbit. Perhaps the image morphology and unusual brightening and fading of P/2020 MK4 were due to a partial disintegration event.