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Rare variable star 34 EP

HD 698

RA 2.9048° · Dec 58.2118° · star

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Score breakdown

· 6 badges
34 pts · Rare
Rare 50 pts → Epic
  • Bright giant +12
  • Hot blue B-type star +6
  • Variable star +5
  • Never sets (northern circumpolar) +4
  • Gently variable +4
  • A named variable star +3
Total score 34

16 more points to reach Epic.

Badges

  • Variable star · +5
  • Never sets (northern circumpolar) · +4
  • Hot blue B-type star · +6
  • Bright giant · +12
  • Gently variable · +4
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads B5II: 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 bright giant, well on its way to the largest stars there are.
  • 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 Cassiopeia.
  • 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 September — 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
-12.91
bv
0.137
constellation
Cas
luminosity
12705741.0521
mag
7.09
name
HD 698
spect
B5II: SB
var amplitude
0.06
var designation
V742
var max
7.058
var min
7.118

About HD 698

HD 698 is a rare variable star. It sits in the constellation Cas, shines at apparent magnitude 7.09 and has spectral type B5II: SB.

Its spectrum reads B5II: 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 698 in the constellation Cas. At apparent magnitude 7.09, it is an easy target for binoculars.

Like any astronomical target, HD 698 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 698 is a rare variable star

HD 698 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, Never sets (northern circumpolar), Hot blue B-type star, Bright giant, 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.