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Uncommon star 29 EP

HD 105256

RA 181.7971° · Dec -61.2644° · 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

Hard to believe

  • True brightness. It pours out about 2.1 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 B2/B3II/III — 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 9.1 you'll want a small backyard telescope, 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 8770 K, against the Sun's 5778 K.

Properties

absmag
-10.95
bv
0.128
constellation
Cru
luminosity
2089296.1309
mag
9.05
name
HD 105256
spect
B2/B3II/III

About HD 105256

HD 105256 is an uncommon star. It sits in the constellation Cru, shines at apparent magnitude 9.05 and has spectral type B2/B3II/III.

Its spectrum reads B2/B3II/III — 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 105256 in the constellation Cru. At apparent magnitude 9.05, a small backyard telescope will bring it into view.

Like any astronomical target, HD 105256 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 105256 is an uncommon star

HD 105256 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.