About Castor
Castor is a common star. It lies about 50.9 light-years from Earth, sits in the constellation Gem, shines at apparent magnitude 1.58 and has spectral type A2Vm.
Notable enough to have earned a proper name, not just a catalogue number.
Common star 19 EP
Castor
RA 113.6495° · Dec 31.8883° · star
Score breakdown
· 3 badgesCommon 24 pts → Uncommon
- Naked-eye visible +8
- Has a proper name +8
- Star +3
Total score 19
5 more points to reach Uncommon.
Badges
- Star · +3
- Naked-eye visible · +8
- Has a proper name · +8
Trivia
Could we get there?
- Verdict. Hopelessly far for any craft humanity can build today.
Getting there
- Aboard Voyager 1. ≈ 893.9 thousand years at Voyager 1's speed (17 km/s).
- Fastest probe ever. ≈ 79.4 thousand years even at the Parker Solar Probe's 192 km/s.
- At 10% light speed. ≈ 509 years in a starship at a tenth of light speed.
- Distance. 50.9 light-years from Earth.
Look-back time
- Look-back time. The light you'd see left around the year 1975.
Saying hello
- Say hello. A radio message and its reply would take 102 years round-trip.
How we found it
- Named. Notable enough to have earned a proper name, not just a catalogue number.
Properties
- absmag
- 0.615
- bv
- 0.034
- constellation
- Gem
- dist ly
- 50.8666
- mag
- 1.58
- name
- Castor
- named
- yes
- spect
- A2Vm
How to see it
Look for Castor in the constellation Gem. At apparent magnitude 1.58, it can be glimpsed with the unaided eye under dark skies.
Like any astronomical target, Castor 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 Castor is a common star
Castor scores 19 points on Spacedle's rarity scale, which places it in the common tier. Another 5 points would lift it into a rarer tier.
That score comes from 3 science badges — Star, Naked-eye visible and Has a proper name — 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.