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Epic variable star 55 EP

HD 186665

RA 296.6087° · Dec -18.1518° · star

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Score breakdown

· 7 badges
55 pts · Epic
Epic 78 pts → Anomaly
  • Carbon star (sooty red) +24
  • Toward the galactic centre +8
  • Deep red star +8
  • Variable star +5
  • Gently variable +4
  • On the zodiac +3
  • A named variable star +3
Total score 55

23 more points to reach Anomaly.

Badges

  • Variable star · +5
  • Toward the galactic centre · +8
  • On the zodiac · +3
  • Carbon star (sooty red) · +24
  • Deep red star · +8
  • Gently variable · +4
  • A named variable star · +3

Trivia

Hard to believe

  • True brightness. It pours out about 1.9 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 C — a carbon star, wrapped in so much soot that its light is filtered to a deep ruby red.
  • 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 9.1 you'll want a small backyard telescope, 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 July — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out deep orange-red (B−V 2.6) — one of the coolest surfaces a star can have while still fusing.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 2650 K, against the Sun's 5778 K.

Properties

absmag
-10.87
bv
2.6
constellation
Sgr
luminosity
1940885.8776
mag
9.13
name
HD 186665
spect
C
var amplitude
0.35
var designation
UW
var max
8.943
var min
9.293

About HD 186665

HD 186665 is an epic variable star. It sits in the constellation Sgr, shines at apparent magnitude 9.13 and has spectral type C.

Its spectrum reads C — a carbon star, wrapped in so much soot that its light is filtered to a deep ruby red.

How to see it

Look for HD 186665 in the constellation Sgr. At apparent magnitude 9.13, a small backyard telescope will bring it into view.

Like any astronomical target, HD 186665 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 186665 is an epic variable star

HD 186665 scores 55 points on Spacedle's rarity scale, which places it in the epic tier. Another 23 points would lift it into a rarer tier.

That score comes from 7 science badges — Variable star, Toward the galactic centre, On the zodiac, Carbon star (sooty red), Deep red 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.