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Common star 21 EP

HD 229239

RA 306.0273° · Dec 38.4926° · star

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Score breakdown

· 3 badges
21 pts · Common
Common 22 pts → Uncommon
  • Bright giant +12
  • Hot blue B-type star +6
  • Star +3
Total score 21

1 more point to reach Uncommon.

Badges

  • Star · +3
  • Hot blue B-type star · +6
  • Bright giant · +12

Trivia

Hard to believe

  • True brightness. It pours out about 2.2 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 B0II — 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 bright giant, well on its way to the largest stars there are.

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 Cygnus.
  • 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 July — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out yellow (B−V 0.7) — almost exactly the Sun's own shade — a stellar twin in colour, if not in size.
  • 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
-11.01
bv
0.732
constellation
Cyg
luminosity
2208004.733
mag
8.99
name
HD 229239
spect
B0II

Nearby objects

About HD 229239

HD 229239 is a common star. It sits in the constellation Cyg, shines at apparent magnitude 8.99 and has spectral type B0II.

Its spectrum reads B0II — 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 229239 in the constellation Cyg. At apparent magnitude 8.99, it is an easy target for binoculars.

Like any astronomical target, HD 229239 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 229239 is a common star

HD 229239 scores 21 points on Spacedle's rarity scale, which places it in the common tier. Another 1 point would lift it into a rarer tier.

That score comes from 3 science badges — Star, Hot blue B-type star and Bright giant — 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.