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Rare variable star 38 EP

HD 104631

RA 180.7348° · Dec -62.1753° · star

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Score breakdown

· 6 badges
38 pts · Rare
Rare 50 pts → Epic
  • Bright giant +12
  • Under the Southern Cross +8
  • Hot blue B-type star +6
  • Variable star +5
  • Gently variable +4
  • A named variable star +3
Total score 38

12 more points to reach Epic.

Badges

  • Variable star · +5
  • Under the Southern Cross · +8
  • 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 B1II — 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 6.8 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Crux.
  • Southern sky only. So far south it never rises for most of the northern hemisphere. To see it you'd have to travel to Chile, South Africa or Australia.
  • Best time of year. It stands highest in the middle of the night around March — 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) — 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
-13.22
bv
0.043
constellation
Cru
luminosity
16904409.3164
mag
6.78
name
HD 104631
spect
B1II
var amplitude
0.06
var designation
DE
var max
6.745
var min
6.805

Nearby objects

About HD 104631

HD 104631 is a rare variable star. It sits in the constellation Cru, shines at apparent magnitude 6.78 and has spectral type B1II.

Its spectrum reads B1II — 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 104631 in the constellation Cru. At apparent magnitude 6.78, it is an easy target for binoculars.

Like any astronomical target, HD 104631 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 104631 is a rare variable star

HD 104631 scores 38 points on Spacedle's rarity scale, which places it in the rare tier. Another 12 points would lift it into a rarer tier.

That score comes from 6 science badges — Variable star, Under the Southern Cross, 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.