Rare variable star 42 EP

HD 181700

RA 290.6995° · Dec -32.5032° · star

Loading sky survey…

🌌 View in 3D star map

Tonight’s visibility

Computing the sky for your location…

Score breakdown

· 8 badges

42 pts · Rare

Rare 50 pts → Epic

Toward the galactic centre +8
Deep red star +8
Giant star +6
Variable star +5
Cool red M-type star +5
Gently variable +4
On the zodiac +3
A named variable star +3

Total score 42

8 more points to reach Epic.

Badges

Variable star · +5
Toward the galactic centre · +8
On the zodiac · +3
Cool red M-type star · +5
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 5.1 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 M2III — an M-type red star — and M stars are the silent majority: roughly three of every four stars in the galaxy are one.
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 8.1 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 deep orange-red (B−V 1.7) — one of the coolest surfaces a star can have while still fusing.

Properties

absmag: -11.93
bv: 1.681
constellation: Sgr
luminosity: 5152286.4458
mag: 8.07
name: HD 181700
spect: M2III
var amplitude: 0.16
var designation: V4416
var max: 7.981
var min: 8.141

Nearby objects

About HD 181700

HD 181700 is a rare variable star. It sits in the constellation Sgr, shines at apparent magnitude 8.07 and has spectral type M2III.

Its spectrum reads M2III — an M-type red star — and M stars are the silent majority: roughly three of every four stars in the galaxy are one.

How to see it

Look for HD 181700 in the constellation Sgr. At apparent magnitude 8.07, it is an easy target for binoculars.

Like any astronomical target, HD 181700 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 181700 is a rare variable star

HD 181700 scores 42 points on Spacedle's rarity scale, which places it in the rare tier. Another 8 points would lift it into a rarer tier.

That score comes from 8 science badges — Variable star, Toward the galactic centre, On the zodiac, Cool red M-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.