Achird is a yellow-white class G hydrogen-fusing dwarf (variously G0 to G3, we adopt the latter) with a surface temperature of 5730 Kelvin, just a bit cooler than the Sun.
Achird (stars.astro.illinois.edu)ACHIRD (Eta Cassiopeiae). At almost fourth magnitude (3.44) and faint to the eye, and not a part of the traditional outline of Cassiopeia, Achird is often neglected.