Psi² Aquarii

Southward of the the Circlet in Pisces, and close to the Ecliptic as it passes through Aquarius, lies a group of three comparatively faint stars. These stars share the designation 'Psi Aquarii', though in fact they are entirely unrelated to one another, apart from the fact that they fall close to the same line of sight as seen from Earth. Psi² is the most distant of the three at some four hundred light years from the Solar System, which places it nearly three times as far away as Psi¹, the nearest of the three.

Psi² Aquarii is a blue star of the class known as 'Be stars', or more precisely in this case 'periodic Be stars', as its magnitude shows a slight but regular variation over a period of almost exactly a day. The star, which is more than four times the Sun's diameter, rotates very rapidly on its axis, and erupts material into space as it does so. This erupted matter forms a circumstellar disc that extends outwards to form a ring surrounding the star itself.