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Rare variable star 42 EP

HD 188338

RA 299.0113° · Dec -36.6679° · star

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Score breakdown

· 8 badges
42 pts · Rare
Rare 50 pts → Epic
  • Toward the galactic centre +8
  • Deep red star +8
  • Giant star +6
  • Variable star +5
  • Cool red M-type star +5
  • Gently variable +4
  • On the zodiac +3
  • A named variable star +3
Total score 42

8 more points to reach Epic.

Badges

  • Variable star · +5
  • Toward the galactic centre · +8
  • On the zodiac · +3
  • Cool red M-type star · +5
  • Giant star · +6
  • Deep red star · +8
  • Gently variable · +4
  • A named variable star · +3

Trivia

Hard to believe

  • True brightness. It pours out about 2.8 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 M1/M2III — an M-type red star — and M stars are the silent majority: roughly three of every four stars in the galaxy are one.
  • 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 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 1.6) — one of the coolest surfaces a star can have while still fusing.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 3630 K, against the Sun's 5778 K.

Properties

absmag
-11.3
bv
1.616
constellation
Sgr
luminosity
2884031.5031
mag
8.7
name
HD 188338
spect
M1/M2III
var amplitude
0.18
var designation
V4426
var max
8.587
var min
8.767

About HD 188338

HD 188338 is a rare variable star. It sits in the constellation Sgr, shines at apparent magnitude 8.7 and has spectral type M1/M2III.

Its spectrum reads M1/M2III — an M-type red star — and M stars are the silent majority: roughly three of every four stars in the galaxy are one.

How to see it

Look for HD 188338 in the constellation Sgr. At apparent magnitude 8.7, it is an easy target for binoculars.

Like any astronomical target, HD 188338 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 188338 is a rare variable star

HD 188338 scores 42 points on Spacedle's rarity scale, which places it in the rare tier. Another 8 points would lift it into a rarer tier.

That score comes from 8 science badges — Variable star, Toward the galactic centre, On the zodiac, Cool red M-type star, Giant star, 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.