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Rare star 38 EP

HD 8768

RA 22.0131° · Dec 63.2825° · star

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Score breakdown

· 4 badges
38 pts · Rare
Rare 50 pts → Epic
  • Blazing O-type star +26
  • Subgiant (leaving the main sequence) +5
  • Never sets (northern circumpolar) +4
  • Star +3
Total score 38

12 more points to reach Epic.

Badges

  • Star · +3
  • Never sets (northern circumpolar) · +4
  • Blazing O-type star · +26
  • Subgiant (leaving the main sequence) · +5

Trivia

Hard to believe

  • True brightness. It pours out about 2.8 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 O9.5IV — an O-type star — the hottest, rarest main class there is. Fewer than one star in a million is an O, and none of them lasts long.
  • Where it is in life. It is a subgiant, caught in the act of leaving the main sequence as the hydrogen in its core runs out.

Find it in the sky

  • How to spot it. At magnitude 8.7 it is just past naked-eye reach — ordinary binoculars will pull it in, 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 October — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out yellow-white (B−V 0.4) — a shade brighter and crisper than our own Sun.
  • 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.

Properties

absmag
-11.28
bv
0.39
constellation
Cas
luminosity
2831391.9958
mag
8.72
name
HD 8768
spect
O9.5IV

About HD 8768

HD 8768 is a rare star. It sits in the constellation Cas, shines at apparent magnitude 8.72 and has spectral type O9.5IV.

Its spectrum reads O9.5IV — an O-type star — the hottest, rarest main class there is. Fewer than one star in a million is an O, and none of them lasts long.

How to see it

Look for HD 8768 in the constellation Cas. At apparent magnitude 8.72, it is an easy target for binoculars.

Like any astronomical target, HD 8768 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 8768 is a rare star

HD 8768 scores 38 points on Spacedle's rarity scale, which places it in the rare tier. Another 12 points would lift it into a rarer tier.

That score comes from 4 science badges — Star, Never sets (northern circumpolar), Blazing O-type star and Subgiant (leaving the main sequence) — 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.