← Back to dex
Rare variable star 34 EP

HD 232121

RA 2.6753° · Dec 54.8915° · star

Loading sky survey…
🌌 View in 3D star map
Tonight’s visibility

Computing the sky for your location…

Score breakdown

· 6 badges
34 pts · Rare
Rare 50 pts → Epic
  • Strongly variable +10
  • Hot blue B-type star +6
  • Giant star +6
  • Variable star +5
  • Never sets (northern circumpolar) +4
  • A named variable star +3
Total score 34

16 more points to reach Epic.

Badges

  • Variable star · +5
  • Never sets (northern circumpolar) · +4
  • Hot blue B-type star · +6
  • Giant star · +6
  • Strongly variable · +10
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads B7IIIe+K3III — a blue-white B-type star, with a surface tens of thousands of degrees hot and a life measured in tens of millions of years.
  • Where it is in life. It is a giant. It has already exhausted its core hydrogen and swollen up enormously in response.
  • It changes. This star does not hold still: its brightness rises and falls on a rhythm of hours, days or years, either pulsing in size or being eclipsed by a companion.

Sense of scale

  • In perspective. Far away by human standards, yet still a local address inside the Milky Way's spiral arms.

Find it in the sky

  • How to spot it. At magnitude 9 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Cassiopeia.
  • Northern sky. It rides the northern half of the sky — an easier target the further north you are.
  • Best time of year. It stands highest in the middle of the night around September — that's when to go looking.

Could we get there?

  • Verdict. Hopelessly far for any craft humanity can build today.

Properties

absmag
2.102
bv
0.674
constellation
Cas
dist ly
771.0543
luminosity
12.5661
mag
8.97
name
HD 232121
spect
B7IIIe+K3III
var amplitude
0.71
var designation
SX
var max
8.868
var min
9.578

About HD 232121

HD 232121 is a rare variable star. It lies about 771.1 light-years from Earth, sits in the constellation Cas, shines at apparent magnitude 8.97 and has spectral type B7IIIe+K3III.

Its spectrum reads B7IIIe+K3III — a blue-white B-type star, with a surface tens of thousands of degrees hot and a life measured in tens of millions of years.

How to see it

Look for HD 232121 in the constellation Cas. At apparent magnitude 8.97, it is an easy target for binoculars.

Like any astronomical target, HD 232121 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.

Why HD 232121 is a rare variable star

HD 232121 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 6 science badges — Variable star, Never sets (northern circumpolar), Hot blue B-type star, Giant star, Strongly 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.