← Back to dex
Rare star 38 EP

HD 164438

RA 270.4678° · Dec -19.1061° · star

Loading sky survey…
🌌 View in 3D star map
Tonight’s visibility

Computing the sky for your location…

Score breakdown

· 5 badges
38 pts · Rare
Rare 50 pts → Epic
  • Supergiant +18
  • Toward the galactic centre +8
  • Hot blue B-type star +6
  • Star +3
  • On the zodiac +3
Total score 38

12 more points to reach Epic.

Badges

  • Star · +3
  • Toward the galactic centre · +8
  • On the zodiac · +3
  • Hot blue B-type star · +6
  • Supergiant · +18

Trivia

What it actually is

  • Spectral class. Its spectrum reads B0.5Iab — 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 supergiant. Drop it where the Sun is and its surface would engulf the inner planets.

Find it in the sky

  • How to spot it. At magnitude 7.5 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Sagittarius.
  • 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 brilliant white (B−V 0.2) — 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 7800 K, against the Sun's 5778 K.

Properties

absmag
-12.52
bv
0.249
constellation
Sgr
luminosity
8871560.1204
mag
7.48
name
HD 164438
spect
B0.5Iab

About HD 164438

HD 164438 is a rare star. It sits in the constellation Sgr, shines at apparent magnitude 7.48 and has spectral type B0.5Iab.

Its spectrum reads B0.5Iab — 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 164438 in the constellation Sgr. At apparent magnitude 7.48, it is an easy target for binoculars.

Like any astronomical target, HD 164438 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 164438 is a rare star

HD 164438 scores 38 points on Spacedle's rarity scale, which places it in the rare tier. Another 12 points would lift it into a rarer tier.

That score comes from 5 science badges — Star, Toward the galactic centre, On the zodiac, 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.