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Uncommon star 26 EP

HD 12740

RA 31.5475° · Dec 49.1563° · star

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Score breakdown

· 4 badges
26 pts · Uncommon
Uncommon 34 pts → Rare
  • Bright giant +12
  • Hot blue B-type star +6
  • Blue-white star +5
  • Star +3
Total score 26

8 more points to reach Rare.

Badges

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

Trivia

What it actually is

  • Spectral class. Its spectrum reads B1.5II — 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 7.9 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Perseus.
  • Northern sky. It rides the northern half of the sky — an easier target the further north you are.
  • Best time of year. It stands highest in the middle of the night around October — 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 10800 K, against the Sun's 5778 K.

Properties

absmag
-12.07
bv
-0.05
constellation
Per
luminosity
5861381.6451
mag
7.93
name
HD 12740
spect
B1.5II

About HD 12740

HD 12740 is an uncommon star. It sits in the constellation Per, shines at apparent magnitude 7.93 and has spectral type B1.5II.

Its spectrum reads B1.5II — 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 12740 in the constellation Per. At apparent magnitude 7.93, it is an easy target for binoculars.

Like any astronomical target, HD 12740 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 12740 is an uncommon star

HD 12740 scores 26 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 8 points would lift it into a rarer tier.

That score comes from 4 science badges — Star, 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.