← Back to dex
Uncommon star 27 EP

HD 194839

RA 306.5898° · Dec 41.3793° · star

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

Computing the sky for your location…

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

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 7.5 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Cygnus.
  • 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 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 0.8) — 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.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 5130 K, against the Sun's 5778 K.

Properties

absmag
-12.53
bv
0.85
constellation
Cyg
luminosity
8953647.6555
mag
7.47
name
HD 194839
spect
B0.5Ia

About HD 194839

HD 194839 is an uncommon star. It sits in the constellation Cyg, shines at apparent magnitude 7.47 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 194839 in the constellation Cyg. At apparent magnitude 7.47, it is an easy target for binoculars.

Like any astronomical target, HD 194839 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 194839 is an uncommon star

HD 194839 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.