SU Persei

SU Persei is a red supergiant star located in the constellation of Perseus. It is located within the Double Cluster, 7,250 light-years away. It is a semiregular variable star that ranges in brightness from magnitude 7.2 to 8.7, which makes it too faint to be seen with the naked eye, but can be seen with binoculars or a telescope.
SU Persei was imaged by the CHARA array in 2015, 2016, 2019, 2020, and 2021. Observations during 2015 and 2016 with CHARA show that the star has an angular diameter between 3.51 and 3.68 milliarcseconds. Considering its large distance from Earth, this results in a radius between 1,044 and 1,139 times that of the Sun, making it one of the largest stars known.
SU Persei is losing mass at a rate of per year, via a stellar wind.
In 1907, Henrietta Swan Leavitt discovered that the star's brightness varies by examining photographic plates. It was given its variable star designation, SU Persei, in 1908.