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Common variable star 17 EP

HD 149250

RA 249.8378° · Dec -70.1686° · star

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Score breakdown

· 4 badges
17 pts · Common
Common 22 pts → Uncommon
  • Variable star +5
  • White A-type star +5
  • Gently variable +4
  • A named variable star +3
Total score 17

5 more points to reach Uncommon.

Badges

  • Variable star · +5
  • White A-type star · +5
  • Gently variable · +4
  • A named variable star · +3

Trivia

Hard to believe

  • True brightness. It pours out about 1.6 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 Ap EuCr(Sr) — 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.

Find it in the sky

  • How to spot it. At magnitude 9.3 you'll want a small backyard telescope, over in Triangulum Australe.
  • 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 May — that's when to go looking.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out brilliant white (B−V 0) — hotter and whiter than the Sun, the colour of Sirius or Vega.
  • 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
-10.71
bv
0.049
constellation
TrA
luminosity
1674942.876
mag
9.29
name
HD 149250
spect
Ap EuCr(Sr)
var amplitude
0.12
var designation
MU
var max
9.231
var min
9.351

Nearby objects

About HD 149250

HD 149250 is a common variable star. It sits in the constellation TrA, shines at apparent magnitude 9.29 and has spectral type Ap EuCr(Sr).

Its spectrum reads Ap EuCr(Sr) — 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 149250 in the constellation TrA. At apparent magnitude 9.29, a small backyard telescope will bring it into view.

Like any astronomical target, HD 149250 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 149250 is a common variable star

HD 149250 scores 17 points on Spacedle's rarity scale, which places it in the common tier. Another 5 points would lift it into a rarer tier.

That score comes from 4 science badges — Variable star, White A-type 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.