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Uncommon star 22 EP

HD 211157

RA 333.9135° · Dec -24.5835° · star

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Score breakdown

· 5 badges
22 pts · Uncommon
Uncommon 34 pts → Rare
  • Hot blue B-type star +6
  • Subgiant (leaving the main sequence) +5
  • Blue-white star +5
  • Star +3
  • On the zodiac +3
Total score 22

12 more points to reach Rare.

Badges

  • Star · +3
  • On the zodiac · +3
  • Hot blue B-type star · +6
  • Subgiant (leaving the main sequence) · +5
  • Blue-white star · +5

Trivia

Hard to believe

  • True brightness. It pours out about 1.5 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 B9IV — 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 subgiant, caught in the act of leaving the main sequence as the hydrogen in its core runs out.

Find it in the sky

  • How to spot it. At magnitude 9.4 you'll want a small backyard telescope, over in Aquarius.
  • 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 August — 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.

Properties

absmag
-10.62
bv
-0.105
constellation
Aqr
luminosity
1541700.4529
mag
9.38
name
HD 211157
spect
B9IV

About HD 211157

HD 211157 is an uncommon star. It sits in the constellation Aqr, shines at apparent magnitude 9.38 and has spectral type B9IV.

Its spectrum reads B9IV — 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 211157 in the constellation Aqr. At apparent magnitude 9.38, a small backyard telescope will bring it into view.

Like any astronomical target, HD 211157 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 211157 is an uncommon star

HD 211157 scores 22 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 12 points would lift it into a rarer tier.

That score comes from 5 science badges — Star, On the zodiac, Hot blue B-type star, Subgiant (leaving the main sequence) 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.