Rare variable star 37 EP

HD 177559

RA 286.4911° · Dec -19.4813° · star

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Score breakdown

· 7 badges

37 pts · Rare

Rare 50 pts → Epic

Strongly variable +10
Toward the galactic centre +8
Hot blue B-type star +6
Variable star +5
On the zodiac +3
A named variable star +3
Main-sequence star +2

Total score 37

13 more points to reach Epic.

Badges

Variable star · +5
Toward the galactic centre · +8
On the zodiac · +3
Hot blue B-type star · +6
Main-sequence star · +2
Strongly variable · +10
A named variable star · +3

Trivia

Hard to believe

True brightness. It pours out about 4.4 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 B2/3V(n) — 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.
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 8.2 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Sagittarius.
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 July — 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: -11.77
bv: 0.01
constellation: Sgr
luminosity: 4446312.6747
mag: 8.23
name: HD 177559
spect: B2/3V(n)
var amplitude: 0.59
var designation: V4197
var max: 8.007
var min: 8.597

Nearby objects

About HD 177559

HD 177559 is a rare variable star. It sits in the constellation Sgr, shines at apparent magnitude 8.23 and has spectral type B2/3V(n).

Its spectrum reads B2/3V(n) — 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 177559 in the constellation Sgr. At apparent magnitude 8.23, it is an easy target for binoculars.

Like any astronomical target, HD 177559 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 177559 is a rare variable star

HD 177559 scores 37 points on Spacedle's rarity scale, which places it in the rare tier. Another 13 points would lift it into a rarer tier.

That score comes from 7 science badges — Variable star, Toward the galactic centre, On the zodiac, Hot blue B-type star, Main-sequence star, Strongly 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.