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Uncommon star 26 EP

9 Cas

RA 1.0569° · Dec 62.2877° · star

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Score breakdown

· 5 badges
26 pts · Uncommon
Uncommon 34 pts → Rare
  • Naked-eye visible +8
  • Giant star +6
  • White A-type star +5
  • Never sets (northern circumpolar) +4
  • Star +3
Total score 26

8 more points to reach Rare.

Badges

  • Star · +3
  • Naked-eye visible · +8
  • Never sets (northern circumpolar) · +4
  • White A-type star · +5
  • Giant star · +6

Trivia

What it actually is

  • Spectral class. Its spectrum reads A1III — 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.
  • Where it is in life. It is a giant. It has already exhausted its core hydrogen and swollen up enormously in response.

Find it in the sky

  • How to spot it. At magnitude 5.9 you can see it with your own eyes from a dark site, over in Cassiopeia.
  • 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.
  • Why no green stars. No star ever looks green: a surface hot enough to peak in green also floods out plenty of red and blue, and your eye blends the mixture back to white.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 7630 K, against the Sun's 5778 K.

Properties

absmag
-14.1
bv
0.274
constellation
Cas
luminosity
38018939.6321
mag
5.9
name
9 Cas
spect
A1III

About 9 Cas

9 Cas is an uncommon star. It sits in the constellation Cas, shines at apparent magnitude 5.9 and has spectral type A1III.

Its spectrum reads A1III — 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.

How to see it

Look for 9 Cas in the constellation Cas. At apparent magnitude 5.9, it can be glimpsed with the unaided eye under dark skies.

Like any astronomical target, 9 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.

Why 9 Cas is an uncommon star

9 Cas scores 26 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 8 points would lift it into a rarer tier.

That score comes from 5 science badges — Star, Naked-eye visible, Never sets (northern circumpolar), White A-type star and Giant 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.