← Back to dex
Rare variable star 39 EP

HD 170756

RA 277.5677° · Dec 21.8668° · star

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

Computing the sky for your location…

Score breakdown

· 5 badges
39 pts · Rare
Rare 50 pts → Epic
  • Supergiant +18
  • Strongly variable +10
  • Variable star +5
  • Yellow-white F-type star +3
  • A named variable star +3
Total score 39

11 more points to reach Epic.

Badges

  • Variable star · +5
  • Yellow-white F-type star · +3
  • Supergiant · +18
  • Strongly variable · +10
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads F4Ibpvar — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
  • Where it is in life. It is a supergiant, hundreds of times wider than the Sun.
  • 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 Hercules.
  • Northern sky. It rides the northern half of the sky — an easier target the further north 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 yellow (B−V 0.7) — almost exactly the Sun's own shade — a stellar twin in colour, if not in size.
  • 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.

Properties

absmag
-12.43
bv
0.727
constellation
Her
luminosity
8165823.7136
mag
7.57
name
HD 170756
spect
F4Ibpvar
var amplitude
1.07
var designation
AC
var max
7.308
var min
8.378

Nearby objects

About HD 170756

HD 170756 is a rare variable star. It sits in the constellation Her, shines at apparent magnitude 7.57 and has spectral type F4Ibpvar.

Its spectrum reads F4Ibpvar — an F-type star — a little hotter, whiter and shorter-lived than the Sun.

How to see it

Look for HD 170756 in the constellation Her. At apparent magnitude 7.57, it is an easy target for binoculars.

Like any astronomical target, HD 170756 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 170756 is a rare variable star

HD 170756 scores 39 points on Spacedle's rarity scale, which places it in the rare tier. Another 11 points would lift it into a rarer tier.

That score comes from 5 science badges — Variable star, Yellow-white F-type star, Supergiant, 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.