About HD 102909
HD 102909 is a common star. It sits in the constellation UMa, shines at apparent magnitude 7.17 and has spectral type G8III.
Its spectrum reads G8III — a G-type star: the very same spectral class as our own Sun.
Common star 21 EP
HD 102909
RA 177.7422° · Dec 33.6042° · star
Score breakdown
· 4 badgesCommon 22 pts → Uncommon
- Sun-like G-type star +8
- Giant star +6
- Never sets (northern circumpolar) +4
- Star +3
Total score 21
1 more point to reach Uncommon.
Badges
- Star · +3
- Never sets (northern circumpolar) · +4
- Sun-like G-type star · +8
- Giant star · +6
Trivia
What it actually is
- Spectral class. Its spectrum reads G8III — a G-type star: the very same spectral class as our own Sun.
- Where it is in life. It is a giant. It has already exhausted its core hydrogen and swollen up enormously in response.
Find it in the sky
- How to spot it. At magnitude 7.2 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Ursa Major.
- 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 March — 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.
By the numbers
- Surface temperature. Its colour puts the surface at roughly 4670 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
- -12.83
- bv
- 1.031
- constellation
- UMa
- luminosity
- 11803206.3565
- mag
- 7.17
- name
- HD 102909
- spect
- G8III
How to see it
Look for HD 102909 in the constellation UMa. At apparent magnitude 7.17, it is an easy target for binoculars.
Like any astronomical target, HD 102909 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 102909 is a common star
HD 102909 scores 21 points on Spacedle's rarity scale, which places it in the common tier. Another 1 point would lift it into a rarer tier.
That score comes from 4 science badges — Star, Never sets (northern circumpolar), Sun-like G-type star and Giant 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.