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Uncommon star 29 EP

HD 104171

RA 179.9203° · Dec -60.8031° · star

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Score breakdown

· 4 badges
29 pts · Uncommon
Uncommon 34 pts → Rare
  • Bright giant +12
  • Under the Southern Cross +8
  • Hot blue B-type star +6
  • Star +3
Total score 29

5 more points to reach Rare.

Badges

  • Star · +3
  • Under the Southern Cross · +8
  • Hot blue B-type star · +6
  • Bright giant · +12

Trivia

What it actually is

  • Spectral class. Its spectrum reads 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.
  • 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 7.8 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Crux.
  • Southern sky only. So far south it never rises for most of the northern hemisphere. To see it you'd have to travel to Chile, South Africa or Australia.
  • Best time of year. It stands highest in the middle of the night around March — 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 0.1) — 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 8880 K, against the Sun's 5778 K.

Properties

absmag
-12.21
bv
0.116
constellation
Cru
luminosity
6668067.6921
mag
7.79
name
HD 104171
spect
B9II

About HD 104171

HD 104171 is an uncommon star. It sits in the constellation Cru, shines at apparent magnitude 7.79 and has spectral type B9II.

Its spectrum reads 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 104171 in the constellation Cru. At apparent magnitude 7.79, it is an easy target for binoculars.

Like any astronomical target, HD 104171 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 104171 is an uncommon star

HD 104171 scores 29 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 5 points would lift it into a rarer tier.

That score comes from 4 science badges — Star, Under the Southern Cross, 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.