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Rare variable star 47 EP

HD 165812

RA 272.1872° · Dec -22.1607° · star

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Score breakdown

· 8 badges
47 pts · Rare
Rare 50 pts → Epic
  • Bright giant +12
  • Toward the galactic centre +8
  • Distant (over 1,000 light-years) +6
  • 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
  • Distant (over 1,000 light-years) · +6
  • Toward the galactic centre · +8
  • On the zodiac · +3
  • Hot blue B-type star · +6
  • Bright giant · +12
  • Gently variable · +4
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads B1/B2II — 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.
  • 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.

Sense of scale

  • In perspective. Far away by human standards, yet still a local address inside the Milky Way's spiral arms.

Find it in the sky

  • How to spot it. At magnitude 7.9 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.

Could we get there?

  • Verdict. Impossible with our current technology — and the next millennium of it.

Getting there

  • Aboard Voyager 1. ≈ 27.2 million years at Voyager 1's speed (17 km/s).

Properties

absmag
-0.439
bv
0.015
constellation
Sgr
dist ly
1545.7629
luminosity
130.4968
mag
7.94
name
HD 165812
spect
B1/B2II
var amplitude
0.07
var designation
V4382
var max
7.904
var min
7.974

About HD 165812

HD 165812 is a rare variable star. It lies about 1,545.8 light-years from Earth, sits in the constellation Sgr, shines at apparent magnitude 7.94 and has spectral type B1/B2II.

Its spectrum reads B1/B2II — 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 165812 in the constellation Sgr. At apparent magnitude 7.94, it is an easy target for binoculars.

Like any astronomical target, HD 165812 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 165812 is a rare variable star

HD 165812 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 8 science badges — Variable star, Distant (over 1,000 light-years), Toward the galactic centre, On the zodiac, Hot blue B-type star, Bright giant, 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.