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Rare variable star 34 EP

HD 198846

RA 313.0149° · Dec 34.6576° · star

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Score breakdown

· 6 badges
34 pts · Rare
Rare 50 pts → Epic
  • Strongly variable +10
  • Hot blue B-type star +6
  • Variable star +5
  • Subgiant (leaving the main sequence) +5
  • Blue-white star +5
  • A named variable star +3
Total score 34

16 more points to reach Epic.

Badges

  • Variable star · +5
  • Hot blue B-type star · +6
  • Subgiant (leaving the main sequence) · +5
  • Blue-white star · +5
  • Strongly variable · +10
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads B0IVv SB — 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.
  • 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 7.3 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 August — 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.

Properties

absmag
-12.69
bv
-0.09
constellation
Cyg
luminosity
10375284.1582
mag
7.31
name
HD 198846
spect
B0IVv SB
var amplitude
0.58
var designation
Y
var max
7.283
var min
7.863

About HD 198846

HD 198846 is a rare variable star. It sits in the constellation Cyg, shines at apparent magnitude 7.31 and has spectral type B0IVv SB.

Its spectrum reads B0IVv SB — 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 198846 in the constellation Cyg. At apparent magnitude 7.31, it is an easy target for binoculars.

Like any astronomical target, HD 198846 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 198846 is a rare variable star

HD 198846 scores 34 points on Spacedle's rarity scale, which places it in the rare tier. Another 16 points would lift it into a rarer tier.

That score comes from 6 science badges — Variable star, Hot blue B-type star, Subgiant (leaving the main sequence), Blue-white star, Strongly 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.