Abell 85 (CTB 1)

Abell 85, which is also cataloged as CTB 1, is a faint supernova remnant. It is the expanding debris cloud left behind after a massive star exploded at the end of its life cycle. It presents a stunning visual target for specialized astrophotography.

The object was independently cataloged at different times by different astronomical surveys. It appears in George Abell's 1955 catalog of planetary nebulae, but the CTB 1 designation comes from the Caltech (California Institute of Technology) radio source catalog B. This double designation reflects the fact that it emits strongly in radio frequencies.

Abell 85 is located in the northern sky within the constellation Cassiopeia. The constellation is easily recognizable by amateur astronomers due to its distinct "W" shape. It sits relatively close to the plane of the Milky Way galaxy.

Visually, the supernova remnant is noted for its distinct, nearly perfectly circular optical structure. Because it is incredibly faint, it requires very long exposure times and specialized narrowband filters to capture its glowing filaments. To the naked eye, it is completely invisible, but astrophotographers often reveal it as a glowing ring.