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Rare variable star 37 EP

HD 104705

RA 180.8496° · Dec -62.6961° · star

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Score breakdown

· 7 badges
37 pts · Rare
Rare 50 pts → Epic
  • Under the Southern Cross +8
  • 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 37

13 more points to reach Epic.

Badges

  • Variable star · +5
  • Under the Southern Cross · +8
  • 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 B0.5III — 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 giant. It has already exhausted its core hydrogen and swollen up enormously in response.
  • 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 7.8 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 blue-white (B−V -0) — 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
-12.21
bv
-0.048
constellation
Cru
luminosity
6668067.6921
mag
7.79
name
HD 104705
spect
B0.5III
var amplitude
0.07
var designation
DF
var max
7.757
var min
7.827

About HD 104705

HD 104705 is a rare variable star. It sits in the constellation Cru, shines at apparent magnitude 7.79 and has spectral type B0.5III.

Its spectrum reads B0.5III — 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 104705 in the constellation Cru. At apparent magnitude 7.79, it is an easy target for binoculars.

Like any astronomical target, HD 104705 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 104705 is a rare variable star

HD 104705 scores 37 points on Spacedle's rarity scale, which places it in the rare tier. Another 13 points would lift it into a rarer tier.

That score comes from 7 science badges — Variable star, Under the Southern Cross, 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.