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Uncommon star 27 EP

HD 173438

RA 281.3692° · Dec -4.5996° · star

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Score breakdown

· 3 badges
27 pts · Uncommon
Uncommon 34 pts → Rare
  • Supergiant +18
  • Hot blue B-type star +6
  • Star +3
Total score 27

7 more points to reach Rare.

Badges

  • Star · +3
  • Hot blue B-type star · +6
  • Supergiant · +18

Trivia

Hard to believe

  • True brightness. It pours out about 4.5 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 B0.5Ia — 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 luminous supergiant — among the largest and rarest stars in the galaxy.

Find it in the sky

  • How to spot it. At magnitude 8.2 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Scutum.
  • Seen from everywhere. It sits almost on the celestial equator, so it can be seen from essentially anywhere on Earth.
  • Best time of year. It stands highest in the middle of the night around July — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out orange (B−V 0.9) — cooler than the Sun, and the kind of star that burns steadily for tens of billions of years.
  • 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
-11.8
bv
0.925
constellation
Sct
luminosity
4570881.8961
mag
8.2
name
HD 173438
spect
B0.5Ia

Nearby objects

About HD 173438

HD 173438 is an uncommon star. It sits in the constellation Sct, shines at apparent magnitude 8.2 and has spectral type B0.5Ia.

Its spectrum reads B0.5Ia — 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 173438 in the constellation Sct. At apparent magnitude 8.2, it is an easy target for binoculars.

Like any astronomical target, HD 173438 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 173438 is an uncommon star

HD 173438 scores 27 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 7 points would lift it into a rarer tier.

That score comes from 3 science badges — Star, Hot blue B-type star and Supergiant — 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.