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Uncommon star 32 EP

HD 7099

RA 17.2665° · Dec -72.5382° · star

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Score breakdown

· 4 badges
32 pts · Uncommon
Uncommon 34 pts → Rare
  • Supergiant +18
  • Hot blue B-type star +6
  • Blue-white star +5
  • Star +3
Total score 32

2 more points to reach Rare.

Badges

  • Star · +3
  • Hot blue B-type star · +6
  • Supergiant · +18
  • Blue-white star · +5

Trivia

Hard to believe

  • True brightness. It pours out about 353.2 thousand 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 B2.5Iab: — 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 a supergiant. Drop it where the Sun is and its surface would engulf the inner planets.

Find it in the sky

  • How to spot it. At magnitude 11 you'll want a small backyard telescope, over in Tucana.
  • 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.

Its true colour

  • Its true colour. Measured through blue and visual filters it comes out blue-white (B−V -0) — the hallmark of a surface far hotter than the Sun's.
  • 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
-9.04
bv
-0.049
constellation
Tuc
luminosity
359749.3352
mag
10.96
name
HD 7099
spect
B2.5Iab:

About HD 7099

HD 7099 is an uncommon star. It sits in the constellation Tuc, shines at apparent magnitude 10.96 and has spectral type B2.5Iab:.

Its spectrum reads B2.5Iab: — 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 7099 in the constellation Tuc. At apparent magnitude 10.96, a small backyard telescope will bring it into view.

Like any astronomical target, HD 7099 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 7099 is an uncommon star

HD 7099 scores 32 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 2 points would lift it into a rarer tier.

That score comes from 4 science badges — Star, Hot blue B-type star, Supergiant and Blue-white 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.