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Rare variable star 47 EP

HD 166443

RA 272.8513° · Dec -20.7125° · star

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Score breakdown

· 7 badges
47 pts · Rare
Rare 50 pts → Epic
  • Supergiant +18
  • Toward the galactic centre +8
  • Hot blue B-type star +6
  • Variable star +5
  • Gently variable +4
  • On the zodiac +3
  • A named variable star +3
Total score 47

3 more points to reach Epic.

Badges

  • Variable star · +5
  • Toward the galactic centre · +8
  • On the zodiac · +3
  • Hot blue B-type star · +6
  • Supergiant · +18
  • Gently variable · +4
  • A named variable star · +3

Trivia

Hard to believe

  • True brightness. It pours out about 2.9 million times as much light as the Sun. It only looks ordinary because it is so far away.

What it actually is

  • Spectral class. Its spectrum reads B0.5Iab:ne — 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 supergiant. Drop it where the Sun is and its surface would engulf the inner planets.
  • 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 8.7 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Sagittarius.
  • 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 June — 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 0.2) — hotter and whiter than the Sun, the colour of Sirius or Vega.

Properties

absmag
-11.32
bv
0.199
constellation
Sgr
luminosity
2937649.652
mag
8.68
name
HD 166443
spect
B0.5Iab:ne
var amplitude
0.13
var designation
V4383
var max
8.632
var min
8.762

About HD 166443

HD 166443 is a rare variable star. It sits in the constellation Sgr, shines at apparent magnitude 8.68 and has spectral type B0.5Iab:ne.

Its spectrum reads B0.5Iab:ne — 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 166443 in the constellation Sgr. At apparent magnitude 8.68, it is an easy target for binoculars.

Like any astronomical target, HD 166443 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 166443 is a rare variable star

HD 166443 scores 47 points on Spacedle's rarity scale, which places it in the rare tier. Another 3 points would lift it into a rarer tier.

That score comes from 7 science badges — Variable star, Toward the galactic centre, On the zodiac, Hot blue B-type star, Supergiant, 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.