← Back to dex
Uncommon variable star 30 EP

HD 217224

RA 344.4471° · Dec 68.4072° · star

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

Computing the sky for your location…

Score breakdown

· 6 badges
30 pts · Uncommon
Uncommon 34 pts → Rare
  • Strongly variable +10
  • Hot blue B-type star +6
  • Variable star +5
  • Never sets (northern circumpolar) +4
  • A named variable star +3
  • Main-sequence star +2
Total score 30

4 more points to reach Rare.

Badges

  • Variable star · +5
  • Never sets (northern circumpolar) · +4
  • Hot blue B-type star · +6
  • Main-sequence star · +2
  • Strongly variable · +10
  • A named variable star · +3

Trivia

Hard to believe

  • True brightness. It pours out about 4.7 million times as much light as the Sun. It only looks ordinary because it is so far away.

What it actually is

  • Spectral class. Its spectrum reads B3V — 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 on the main sequence, quietly fusing hydrogen in its core exactly as the Sun does.
  • 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.

Find it in the sky

  • How to spot it. At magnitude 8.2 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Cepheus.
  • Never sets. So far north that from Britain, Canada or northern Europe it never dips below the horizon — it is up every clear night of the year.
  • Best time of year. It stands highest in the middle of the night around September — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out brilliant white (B−V 0.3) — hotter and whiter than the Sun, the colour of Sirius or Vega.

Properties

absmag
-11.85
bv
0.264
constellation
Cep
luminosity
4786300.9232
mag
8.15
name
HD 217224
spect
B3V
var amplitude
0.9
var designation
GT
var max
8.09
var min
8.99

About HD 217224

HD 217224 is an uncommon variable star. It sits in the constellation Cep, shines at apparent magnitude 8.15 and has spectral type B3V.

Its spectrum reads B3V — 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 217224 in the constellation Cep. At apparent magnitude 8.15, it is an easy target for binoculars.

Like any astronomical target, HD 217224 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 217224 is an uncommon variable star

HD 217224 scores 30 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 4 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, Main-sequence 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.