Eta Cassiopeia a true binary system which is only 19.4 light years distant and is easily resolved in small telescopes. The orbit of the secondary star is highly eccentric which brings it as close to the primary star as 36 A.U. which is comparable to the distance of Neptune to our Sun.
AR Cass has the appearance of a small cluster and the proper motions of members A-C-D-F & G suggest a common origin. AR Cass is closest to us at 573 LY while components C-D-F-G vary in distance from 650 to 740 LY. STF 3022 A-B is a physical pair 1,000 LY distant.
The physical pair Leonard 55 are members of the open cluster of NGC 7790 in the constellation of Cassiopeia. It is the only known pair in the Milky Way where both components of a binary system are Classical Cephid Variable Stars. Depending on when it is viewed either one or the other may take pride of place as being the brighter “Primary Star”.
Visible in small scopes as a beautiful triple system , Iota Cass is actually composed of five stars. What we see as the bright “A” component is actually made up of two stars – mags 4.6 & 8.5 – separated by 0.7″. The diminutive C component is also made up of two stars with a separation of only 0.4″.