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Common star 21 EP

HD 137522

RA 232.2480° · Dec -55.6273° · 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

What it actually is

  • Spectral class. Its spectrum reads B8/B9II — 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.

Find it in the sky

  • How to spot it. At magnitude 7.8 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Circinus.
  • Southern sky. It rides the southern half of the sky — an easier target the further south you are.
  • Best time of year. It stands highest in the middle of the night around May — 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 0.3) — 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.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 7390 K, against the Sun's 5778 K.

What's in a name

  • Its catalogue. The HD number is from the Henry Draper Catalogue, in which Annie Jump Cannon personally classified the spectra of nearly 400,000 stars — still the largest such feat by one person.

Properties

absmag
-12.18
bv
0.311
constellation
Cir
luminosity
6486344.3355
mag
7.82
name
HD 137522
spect
B8/B9II

About HD 137522

HD 137522 is a common star. It sits in the constellation Cir, shines at apparent magnitude 7.82 and has spectral type B8/B9II.

Its spectrum reads B8/B9II — 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 137522 in the constellation Cir. At apparent magnitude 7.82, it is an easy target for binoculars.

Like any astronomical target, HD 137522 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 137522 is a common star

HD 137522 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.