Castor
HR 2891 · HIP 36850 · α Gem
👁️ Naked-eye
📋 A written introduction is coming — for now this page shows official values only.
Star
- Apparent magnitude
- 1.58 mag
- Parallax
- 64.12 mas → about 50.9 light-years away
- Spectral type
- A2Vm
- Right ascension
- 113.6495°
- Declination
- 31.8883°
- Designation
- HR 2891
- Bayer designation
- α Gem
- HIP number
- 36850
- IAU name adopted
- 2016-06-30
- Name language
- Greek
- Name origin (IAU)
- From its ancient Greek name Κάστωρ, a character in Greek mythology, the twin of Pollux (β Gem). Reapplied in Early Modern times.
Source:IAU Working Group on Star Names · checked 2026-11-02 ↗ESA Hipparcos Catalogue (ESA Gaia Archive) · checked 2026-11-03 ↗
Related
Constellation
In everyday life
- Light from this object takes about 51 years to reach Earth — the light you see tonight left around AD 1975 (official distance ÷ speed of light).
- At magnitude 1.6 it is bright enough for the naked eye (limit about 6) — look from somewhere dark.
- Declination 31.9° — it rises above the horizon in Seoul (37.6° N), so it is visible from Korea in the right season.
Worked out from this object's official values.