About HD 21771
HD 21771 is an uncommon star. It lies about 2,416 light-years from Earth, sits in the constellation Per and shines at apparent magnitude 7.24.
Its colour puts the surface at roughly 3910 K, against the Sun's 5778 K.
Uncommon star 27 EP
HD 21771
RA 53.0684° · Dec 44.8407° · star
Score breakdown
· 4 badgesUncommon 34 pts → Rare
- Intrinsically luminous (Mv < −2) +10
- Deep red star +8
- Distant (over 1,000 light-years) +6
- Star +3
Total score 27
7 more points to reach Rare.
Badges
- Star · +3
- Distant (over 1,000 light-years) · +6
- Deep red star · +8
- Intrinsically luminous (Mv < −2) · +10
Trivia
Sense of scale
- In perspective. Far away by human standards, yet still a local address inside the Milky Way's spiral arms.
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 Perseus.
- 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 November — that's when to go looking.
Could we get there?
- Verdict. Impossible with our current technology — and the next millennium of it.
Getting there
- Aboard Voyager 1. ≈ 42.5 million years at Voyager 1's speed (17 km/s).
- Fastest probe ever. ≈ 3.8 million years even at the Parker Solar Probe's 192 km/s.
- At 10% light speed. ≈ 24.2 thousand years in a starship at a tenth of light speed.
Properties
- absmag
- -2.108
- bv
- 1.426
- constellation
- Per
- dist ly
- 2415.9702
- luminosity
- 607.0158
- mag
- 7.24
- name
- HD 21771
How to see it
Look for HD 21771 in the constellation Per. At apparent magnitude 7.24, it is an easy target for binoculars.
Like any astronomical target, HD 21771 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 21771 is an uncommon star
HD 21771 scores 27 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 7 points would lift it into a rarer tier.
That score comes from 4 science badges — Star, Distant (over 1,000 light-years), Deep red star and Intrinsically luminous (Mv < −2) — 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.