Rare star 35 EP

HD 106391

RA 183.6302° · Dec -61.9018° · star

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Score breakdown

· 4 badges

35 pts · Rare

Rare 50 pts → Epic

Supergiant +18
Under the Southern Cross +8
Hot blue B-type star +6
Star +3

Total score 35

15 more points to reach Epic.

Badges

Star · +3
Under the Southern Cross · +8
Hot blue B-type star · +6
Supergiant · +18

Trivia

Hard to believe

True brightness. It pours out about 3 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 B3Ia — 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 luminous supergiant — among the largest and rarest stars in the galaxy.

Find it in the sky

How to spot it. At magnitude 8.6 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Crux.
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 March — that's when to go looking.

Its true colour

Its true colour. Measured through blue and visual filters it comes out yellow (B−V 0.8) — almost exactly the Sun's own shade — a stellar twin in colour, if not in size.
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: -11.37
bv: 0.763
constellation: Cru
luminosity: 3076096.8147
mag: 8.63
name: HD 106391
spect: B3Ia

Nearby objects

About HD 106391

HD 106391 is a rare star. It sits in the constellation Cru, shines at apparent magnitude 8.63 and has spectral type B3Ia.

Its spectrum reads B3Ia — 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 106391 in the constellation Cru. At apparent magnitude 8.63, it is an easy target for binoculars.

Like any astronomical target, HD 106391 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 106391 is a rare star

HD 106391 scores 35 points on Spacedle's rarity scale, which places it in the rare tier. Another 15 points would lift it into a rarer tier.

That score comes from 4 science badges — Star, Under the Southern Cross, Hot blue B-type star and Supergiant — 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.