RA 11.4129° · Dec 74.9881° · star
16 more points to reach Epic.
21 Cas is a rare variable star. It lies about 303.4 light-years from Earth, sits in the constellation Cas, shines at apparent magnitude 5.64 and has spectral type A2IV.
Its spectrum reads A2IV — an A-type star: white-hot, typically about twice the Sun's mass, and the class most of the sky's famous bright stars belong to.
Look for 21 Cas in the constellation Cas. At apparent magnitude 5.64, it can be glimpsed with the unaided eye under dark skies.
Like any astronomical target, 21 Cas is best seen from a dark site away from city lights, and when it is above the horizon depends on your latitude and the time of year. The visibility panel above works out tonight's viewing window for your saved location.
21 Cas scores 34 points on Spacedle's rarity scale, which places it in the rare tier. Another 16 points would lift it into a rarer tier.
That score comes from 7 science badges — Variable star, Naked-eye visible, Never sets (northern circumpolar), White A-type star, Subgiant (leaving the main sequence), Gently variable and A named variable star — each earned for a real, measurable property of the object. Rarity on Spacedle is never random: the more remarkable an object's astrophysics, the more badges it collects, the higher it scores, and the rarer it ranks.