SU Ursae Majoris (SU UMa)

SU Ursae Majoris (SU UMa) is the prototype SU Ursae Majoris star. It is located, in the sky, near the tip of the nose of Ursa Major, about 3 degrees northwest of Omicron UMa. The unusual variability of SU UMa was first noted in 1908 by the Russian astronomer L. Ceraski. SU UMa shows normal U Geminorum-type outbursts every 11–17 days and super-outbursts every 153–260 days; its range is from magnitude 15 at minimum to a peak magnitude of 10.8 at super-outburst. Since the defining features of SU UMa stars are a narrow outburst, a super-outburst, and a super-hump, it is strange that for a period of nearly three years in the early 1980s the prototype itself did not exhibit such behavior. Thus, it was questioned whether this variable even belonged to the category named after it! Another absence of super-outburst activity happened between April 1990 and July 1991.