← Back to dex
Rare variable star 37 EP

HD 131699

RA 224.0499° · Dec -35.3876° · star

Loading sky survey…
🌌 View in 3D star map
Tonight’s visibility

Computing the sky for your location…

Score breakdown

· 6 badges
37 pts · Rare
Rare 50 pts → Epic
  • Bright giant +12
  • Deep red star +8
  • Variable star +5
  • Cool red M-type star +5
  • Gently variable +4
  • A named variable star +3
Total score 37

13 more points to reach Epic.

Badges

  • Variable star · +5
  • Cool red M-type star · +5
  • Bright giant · +12
  • Deep red star · +8
  • Gently variable · +4
  • A named variable star · +3

Trivia

Hard to believe

  • True brightness. It pours out about 2.6 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 M2/M3II/III — 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 8.8 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Centaurus.
  • 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 May — 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 1.7) — one of the coolest surfaces a star can have while still fusing.

By the numbers

  • Surface temperature. Its colour puts the surface at roughly 3580 K, against the Sun's 5778 K.

Properties

absmag
-11.22
bv
1.654
constellation
Cen
luminosity
2679168.3248
mag
8.78
name
HD 131699
spect
M2/M3II/III
var amplitude
0.15
var designation
V1020
var max
8.724
var min
8.874

About HD 131699

HD 131699 is a rare variable star. It sits in the constellation Cen, shines at apparent magnitude 8.78 and has spectral type M2/M3II/III.

Its spectrum reads M2/M3II/III — 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 131699 in the constellation Cen. At apparent magnitude 8.78, it is an easy target for binoculars.

Like any astronomical target, HD 131699 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 131699 is a rare variable star

HD 131699 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 6 science badges — Variable star, Cool red M-type star, Bright giant, 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.