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Uncommon star 29 EP

HD 153855

RA 255.8247° · Dec -31.6146° · star

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Score breakdown

· 5 badges
29 pts · Uncommon
Uncommon 34 pts → Rare
  • Bright giant +12
  • Hot blue B-type star +6
  • Blue-white star +5
  • Star +3
  • On the zodiac +3
Total score 29

5 more points to reach Rare.

Badges

  • Star · +3
  • On the zodiac · +3
  • Hot blue B-type star · +6
  • Bright giant · +12
  • Blue-white star · +5

Trivia

What it actually is

  • Spectral class. Its spectrum reads B2II — 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 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Scorpius.
  • 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 June — 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 11140 K, against the Sun's 5778 K.

Properties

absmag
-13.03
bv
-0.073
constellation
Sco
luminosity
14190575.2169
mag
6.97
name
HD 153855
spect
B2II

About HD 153855

HD 153855 is an uncommon star. It sits in the constellation Sco, shines at apparent magnitude 6.97 and has spectral type B2II.

Its spectrum reads B2II — 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 153855 in the constellation Sco. At apparent magnitude 6.97, it is an easy target for binoculars.

Like any astronomical target, HD 153855 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 153855 is an uncommon star

HD 153855 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 5 science badges — Star, On the zodiac, Hot blue B-type star, Bright giant 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.