About HD 189731
HD 189731 is a trash star. It sits in the constellation Vul, shines at apparent magnitude 7.54 and has spectral type G5.
Its spectrum reads G5 — a G-type star: the very same spectral class as our own Sun.
Trash star 11 EP
HD 189731
RA 300.1612° · Dec 24.1492° · star
Score breakdown
· 2 badgesTrash 15 pts → Common
- Sun-like G-type star +8
- Star +3
Total score 11
4 more points to reach Common.
Badges
- Star · +3
- Sun-like G-type star · +8
Trivia
What it actually is
- Spectral class. Its spectrum reads G5 — a G-type star: the very same spectral class as our own Sun.
Find it in the sky
- How to spot it. At magnitude 7.5 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Vulpecula.
- Northern sky. It rides the northern half of the sky — an easier target the further north 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 orange (B−V 1) — cooler than the Sun, and the kind of star that burns steadily for tens of billions of years.
- 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 4850 K, against the Sun's 5778 K.
What's in a name
- Its catalogue. The HD number is from the Henry Draper Catalogue, in which Annie Jump Cannon personally classified the spectra of nearly 400,000 stars — still the largest such feat by one person.
Properties
- absmag
- -12.46
- bv
- 0.955
- constellation
- Vul
- luminosity
- 8394599.8652
- mag
- 7.54
- name
- HD 189731
- spect
- G5
How to see it
Look for HD 189731 in the constellation Vul. At apparent magnitude 7.54, it is an easy target for binoculars.
Like any astronomical target, HD 189731 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 189731 is a trash star
HD 189731 scores 11 points on Spacedle's rarity scale, which places it in the trash tier. Another 4 points would lift it into a rarer tier.
That score comes from 2 science badges — Star and Sun-like G-type 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.