Common star 19 EP

HD 189400

RA 300.2207° · Dec -27.1814° · star

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Score breakdown

· 5 badges

19 pts · Common

Common 22 pts → Uncommon

Toward the galactic centre +8
Star +3
On the zodiac +3
Yellow-white F-type star +3
Main-sequence star +2

Total score 19

3 more points to reach Uncommon.

Badges

Star · +3
Toward the galactic centre · +8
On the zodiac · +3
Yellow-white F-type star · +3
Main-sequence star · +2

Trivia

Hard to believe

True brightness. It pours out about 3.9 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 F3/5V: +A7/9 — an F-type star — a little hotter, whiter and shorter-lived than the Sun.

Find it in the sky

How to spot it. At magnitude 8.4 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 yellow-white (B−V 0.5) — a shade brighter and crisper than our own Sun.
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.

By the numbers

Surface temperature. Its colour puts the surface at roughly 6530 K, against the Sun's 5778 K.

Properties

absmag: -11.64
bv: 0.47
constellation: Sgr
luminosity: 3944573.0208
mag: 8.36
name: HD 189400
spect: F3/5V: +A7/9

Nearby objects

About HD 189400

HD 189400 is a common star. It sits in the constellation Sgr, shines at apparent magnitude 8.36 and has spectral type F3/5V: +A7/9.

Its spectrum reads F3/5V: +A7/9 — an F-type star — a little hotter, whiter and shorter-lived than the Sun.

How to see it

Look for HD 189400 in the constellation Sgr. At apparent magnitude 8.36, it is an easy target for binoculars.

Like any astronomical target, HD 189400 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 189400 is a common star

HD 189400 scores 19 points on Spacedle's rarity scale, which places it in the common tier. Another 3 points would lift it into a rarer tier.

That score comes from 5 science badges — Star, Toward the galactic centre, On the zodiac, Yellow-white F-type star and Main-sequence 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.