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Uncommon star 28 EP

HD 104200

RA 179.9857° · Dec -56.2931° · star

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Score breakdown

· 5 badges
28 pts · Uncommon
Uncommon 34 pts → Rare
  • Under the Southern Cross +8
  • Hot blue B-type star +6
  • Giant star +6
  • Blue-white star +5
  • Star +3
Total score 28

6 more points to reach Rare.

Badges

  • Star · +3
  • Under the Southern Cross · +8
  • Hot blue B-type star · +6
  • Giant star · +6
  • Blue-white star · +5

Trivia

What it actually is

  • Spectral class. Its spectrum reads B1III — 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 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 7.7 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Crux.
  • 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 March — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out blue-white (B−V -0.1) — the hallmark of a surface far hotter than the Sun's.
  • 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 11740 K, against the Sun's 5778 K.

Properties

absmag
-12.3
bv
-0.11
constellation
Cru
luminosity
7244359.6007
mag
7.7
name
HD 104200
spect
B1III

About HD 104200

HD 104200 is an uncommon star. It sits in the constellation Cru, shines at apparent magnitude 7.7 and has spectral type B1III.

Its spectrum reads B1III — 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 104200 in the constellation Cru. At apparent magnitude 7.7, it is an easy target for binoculars.

Like any astronomical target, HD 104200 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 104200 is an uncommon star

HD 104200 scores 28 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 6 points would lift it into a rarer tier.

That score comes from 5 science badges — Star, Under the Southern Cross, Hot blue B-type star, Giant star and Blue-white 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.