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Rare variable star 47 EP

HR 6929

RA 277.3416° · Dec -25.2566° · star

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Score breakdown

· 9 badges
47 pts · Rare
Rare 50 pts → Epic
  • Intrinsically luminous (Mv < −2) +10
  • 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
  • Main-sequence star +2
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
  • Main-sequence star · +2
  • Intrinsically luminous (Mv < −2) · +10
  • Gently variable · +4
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads B2Vnne — 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.
  • Where it is in life. It is on the main sequence, quietly fusing hydrogen in its core exactly as the Sun does.
  • 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 6.6 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.

Properties

absmag
-3.223
bv
0.002
constellation
Sgr
dist ly
3048.1868
luminosity
1695.1183
mag
6.63
name
HR 6929
spect
B2Vnne
var amplitude
0.09
var designation
V4031
var max
6.561
var min
6.651

About HR 6929

HR 6929 is a rare variable star. It lies about 3,048.2 light-years from Earth, sits in the constellation Sgr, shines at apparent magnitude 6.63 and has spectral type B2Vnne.

Its spectrum reads B2Vnne — 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 HR 6929 in the constellation Sgr. At apparent magnitude 6.63, it is an easy target for binoculars.

Like any astronomical target, HR 6929 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 HR 6929 is a rare variable star

HR 6929 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 9 science badges — Variable star, Distant (over 1,000 light-years), Toward the galactic centre, On the zodiac, Hot blue B-type star, Main-sequence star, Intrinsically luminous (Mv < −2) and Gently variable — 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.