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Trash star 14 EP

HD 190991

RA 301.5030° · Dec 40.0650° · star

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Score breakdown

· 3 badges
14 pts · Trash
Trash 15 pts → Common
  • Hot blue B-type star +6
  • Subgiant (leaving the main sequence) +5
  • Star +3
Total score 14

1 more point to reach Common.

Badges

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

Trivia

Hard to believe

  • True brightness. It pours out about 4.4 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 B0IVp — 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 8.2 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 brilliant white (B−V 0.1) — 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.

Properties

absmag
-11.79
bv
0.092
constellation
Cyg
luminosity
4528975.799
mag
8.21
name
HD 190991
spect
B0IVp

Nearby objects

About HD 190991

HD 190991 is a trash star. It sits in the constellation Cyg, shines at apparent magnitude 8.21 and has spectral type B0IVp.

Its spectrum reads B0IVp — 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 190991 in the constellation Cyg. At apparent magnitude 8.21, it is an easy target for binoculars.

Like any astronomical target, HD 190991 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 190991 is a trash star

HD 190991 scores 14 points on Spacedle's rarity scale, which places it in the trash tier. Another 1 point would lift it into a rarer tier.

That score comes from 3 science badges — Star, Hot blue B-type star and Subgiant (leaving the main sequence) — 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.