Z Ursae Minoris was discovered to be a variable star in 1934.[7] It was catalogued as a probable Mira variable, due to its red colour and variations over several hundred days.[8] It was discovered to be a carbon star in a survey published in 1985,[9] and subsequently found also to be hydrogen-deficient.[7] After fading by almost six magnitudes in 1992, it was classified as an R Coronae Borealis variable.[10] It was confirmed as an R Coronae Borealis variable, one of the coolest in the class, after its spectrum was analysed in 2006.[5]
^Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.