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Common variable star 20 EP

HD 10840

RA 26.1373° · Dec -61.0187° · star

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Score breakdown

· 5 badges
20 pts · Common
Common 22 pts → Uncommon
  • Variable star +5
  • White A-type star +5
  • Blue-white star +5
  • A named variable star +3
  • Barely variable (under 0.05 mag) +2
Total score 20

2 more points to reach Uncommon.

Badges

  • Variable star · +5
  • White A-type star · +5
  • Blue-white star · +5
  • Barely variable (under 0.05 mag) · +2
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads Ap Si — an A-type star: white-hot, typically about twice the Sun's mass, and the class most of the sky's famous bright stars belong to.
  • 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 6.8 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Hydrus.
  • Southern sky only. So far south it never rises for most of the northern hemisphere. To see it you'd have to travel to Chile, South Africa or Australia.
  • Best time of year. It stands highest in the middle of the night around October — that's when to go looking.

Could we get there?

  • Verdict. Hopelessly far for any craft humanity can build today.

Getting there

  • Aboard Voyager 1. ≈ 10.3 million years at Voyager 1's speed (17 km/s).

Properties

absmag
0.511
bv
-0.067
constellation
Hyi
dist ly
587.6685
luminosity
54.4001
mag
6.79
name
HD 10840
spect
Ap Si
var amplitude
0.05
var designation
BM
var max
6.767
var min
6.817

About HD 10840

HD 10840 is a common variable star. It lies about 587.7 light-years from Earth, sits in the constellation Hyi, shines at apparent magnitude 6.79 and has spectral type Ap Si.

Its spectrum reads Ap Si — an A-type star: white-hot, typically about twice the Sun's mass, and the class most of the sky's famous bright stars belong to.

How to see it

Look for HD 10840 in the constellation Hyi. At apparent magnitude 6.79, it is an easy target for binoculars.

Like any astronomical target, HD 10840 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 10840 is a common variable star

HD 10840 scores 20 points on Spacedle's rarity scale, which places it in the common tier. Another 2 points would lift it into a rarer tier.

That score comes from 5 science badges — Variable star, White A-type star, Blue-white star, Barely variable (under 0.05 mag) 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.