Omicron Cassiopeiae

Omicron Cassiopeia lies near the southern border of Cassiopeia, where it meets neighbouring Andromeda. The star thus lies approximately halfway between Cassiopeia's central 'Chair' of five bright stars to the north, and the Andromeda Galaxy to the south. It is relatively remote from the Solar System, lying beyond the five stars of Cassiopeia's Chair at a distance approaching seven hundred light years.

The primary star of the system is a shell star, a blue giant that casts off material into space as it rotates. This blue star is more than seven times the Sun's diameter, and emits some six hundred times as much light. Around this primary, another star follows a close orbit that takes less than three years to complete. Much farther out from these two is a bright yellow dwarf, following a much more distant orbit through the system at a distance of about a tenth of a light year from the close central pair.

* Most sources, including the Hipparcos and primary Gaia data, agree on a distance for this star of a little under seven hundred light years. However, the subsequent Gaia data release 3 is at considerable odds with these values. That dataset gives a parallax of 0.5116, which equates (with considerable margin for error) to a distance of about 6,400 light years, or nearly ten times farther than the other measurements. Given the general agreement between the other different datasets, the value of about 693 light years seems to be correct, but the existence of such an extreme outlying value does suggest at least a degree of uncertainty.