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Uncommon variable star 31 EP

HD 55173

RA 107.6276° · Dec -30.6625° · star

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Score breakdown

· 6 badges
31 pts · Uncommon
Uncommon 34 pts → Rare
  • Strongly variable +10
  • Hot blue B-type star +6
  • Variable star +5
  • Blue-white star +5
  • A named variable star +3
  • Main-sequence star +2
Total score 31

3 more points to reach Rare.

Badges

  • Variable star · +5
  • Hot blue B-type star · +6
  • Main-sequence star · +2
  • Blue-white star · +5
  • Strongly variable · +10
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads B3/5V(p) — 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 7.6 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Canis Major.
  • Southern sky. It rides the southern half of the sky — an easier target the further south you are.
  • Best time of year. It stands highest in the middle of the night around January — 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 -0.2) — 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 13010 K, against the Sun's 5778 K.

Properties

absmag
-12.42
bv
-0.175
constellation
CMa
luminosity
8090958.9918
mag
7.58
name
HD 55173
spect
B3/5V(p)
var amplitude
1.03
var designation
FF
var max
7.402
var min
8.432

About HD 55173

HD 55173 is an uncommon variable star. It sits in the constellation CMa, shines at apparent magnitude 7.58 and has spectral type B3/5V(p).

Its spectrum reads B3/5V(p) — 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 55173 in the constellation CMa. At apparent magnitude 7.58, it is an easy target for binoculars.

Like any astronomical target, HD 55173 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 55173 is an uncommon variable star

HD 55173 scores 31 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 3 points would lift it into a rarer tier.

That score comes from 6 science badges — Variable star, Hot blue B-type star, Main-sequence star, 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.