[11] It was first discovered in outburst in 1866 by John Birmingham,[12] though it had been observed earlier as a 10th magnitude star.

[18] Even when at peak magnitude of 2.5, this recurrent nova is dimmer than about 120 brightest stars in the night sky.

[21] The hot component is a white dwarf surrounded by an accretion disc, all hidden inside a dense cloud of material from the red giant.

[24] On 20 April 2016, the Sky & Telescope website reported a sustained brightening since February 2015 from magnitude 10.5 to about 9.2.

[25] By June 2018, the star had dimmed slightly but still remained at an unusually high level of activity.