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Uncommon variable star 23 EP

HD 183794

RA 292.8158° · Dec -2.1102° · star

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Score breakdown

· 5 badges
23 pts · Uncommon
Uncommon 34 pts → Rare
  • Hot blue B-type star +6
  • Variable star +5
  • Blue-white star +5
  • Gently variable +4
  • A named variable star +3
Total score 23

11 more points to reach Rare.

Badges

  • Variable star · +5
  • Hot blue B-type 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+... — 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 7.1 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Aquila.
  • 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 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 12290 K, against the Sun's 5778 K.

Properties

absmag
-12.91
bv
-0.14
constellation
Aql
luminosity
12705741.0521
mag
7.09
name
HD 183794
spect
B5+...
var amplitude
0.43
var designation
V822
var max
6.994
var min
7.424

About HD 183794

HD 183794 is an uncommon variable star. It sits in the constellation Aql, shines at apparent magnitude 7.09 and has spectral type B5+....

Its spectrum reads B5+... — 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 183794 in the constellation Aql. At apparent magnitude 7.09, it is an easy target for binoculars.

Like any astronomical target, HD 183794 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 183794 is an uncommon variable star

HD 183794 scores 23 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 11 points would lift it into a rarer tier.

That score comes from 5 science badges — Variable star, Hot blue B-type 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.