Z Ursae Minoris

Z Ursae Minoris (Z UMi) is a star in the constellation Ursa Minor. It was confirmed to be one of a rare class of stars—R Coronae Borealis variables—after its spectrum was analysed in 2006. Initially observed to be variable in 1934, it suddenly dropped 6 magnitudes in 1992 and was subsequently diagnosed as an RcB star. Up till this point it was thought to have been a long period (Mira) variable.