Uncommon variable star 29 EP

HD 155100

RA 258.2620° · Dec -58.9113° · star

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Score breakdown

· 6 badges

29 pts · Uncommon

Uncommon 34 pts → Rare

Deep red star +8
Giant star +6
Variable star +5
Gently variable +4
Orange K-type star +3
A named variable star +3

Total score 29

5 more points to reach Rare.

Badges

Variable star · +5
Orange K-type star · +3
Giant star · +6
Deep red star · +8
Gently variable · +4
A named variable star · +3

Trivia

Hard to believe

True brightness. It pours out about 4.2 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 K4III: — a K-type star. Orange K dwarfs are the marathon runners of the galaxy, burning steadily for tens of billions of years.
Where it is in life. It is a giant. It has already exhausted its core hydrogen and swollen up enormously in response.
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 8.3 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Ara.
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.

Its true colour

Its true colour. Measured through blue and visual filters it comes out deep orange-red (B−V 1.7) — one of the coolest surfaces a star can have while still fusing.

Properties

absmag: -11.72
bv: 1.687
constellation: Ara
luminosity: 4246195.6395
mag: 8.28
name: HD 155100
spect: K4III:
var amplitude: 0.1
var designation: V856
var max: 8.234
var min: 8.334

Nearby objects

About HD 155100

HD 155100 is an uncommon variable star. It sits in the constellation Ara, shines at apparent magnitude 8.28 and has spectral type K4III:.

Its spectrum reads K4III: — a K-type star. Orange K dwarfs are the marathon runners of the galaxy, burning steadily for tens of billions of years.

How to see it

Look for HD 155100 in the constellation Ara. At apparent magnitude 8.28, it is an easy target for binoculars.

Like any astronomical target, HD 155100 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 155100 is an uncommon variable star

HD 155100 scores 29 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 5 points would lift it into a rarer tier.

That score comes from 6 science badges — Variable star, Orange K-type star, Giant star, Deep red 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.