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Uncommon variable star 29 EP

HD 191980

RA 303.0160° · Dec 15.3578° · star

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Score breakdown

· 6 badges
29 pts · Uncommon
Uncommon 34 pts → Rare
  • Hot blue B-type star +6
  • Giant star +6
  • Variable star +5
  • Blue-white star +5
  • Gently variable +4
  • A named variable star +3
Total score 29

5 more points to reach Rare.

Badges

  • Variable star · +5
  • Hot blue B-type star · +6
  • Giant star · +6
  • Blue-white star · +5
  • Gently variable · +4
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads B5-6IIIp — 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.
  • It changes. This star does not hold still: its brightness rises and falls on a rhythm of hours, days or years, either pulsing in size or being eclipsed by a companion.

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 Aquila.
  • 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 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 12350 K, against the Sun's 5778 K.

Properties

absmag
-12.09
bv
-0.143
constellation
Aql
luminosity
5970352.8658
mag
7.91
name
HD 191980
spect
B5-6IIIp
var amplitude
0.06
var designation
V1357
var max
7.878
var min
7.938

About HD 191980

HD 191980 is an uncommon variable star. It sits in the constellation Aql, shines at apparent magnitude 7.91 and has spectral type B5-6IIIp.

Its spectrum reads B5-6IIIp — 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 191980 in the constellation Aql. At apparent magnitude 7.91, it is an easy target for binoculars.

Like any astronomical target, HD 191980 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 191980 is an uncommon variable star

HD 191980 scores 29 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 5 points would lift it into a rarer tier.

That score comes from 6 science badges — Variable star, Hot blue B-type star, Giant star, Blue-white star, Gently variable and A named variable 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.