✦ Gemini (Gem)
✦ Gemini (Gem)
Subfolder of: Fixed Stars · Constellations
| Field | Value |
|---|---|
| IAU name | Gemini |
| IAU abbreviation | Gem |
| Latin genitive (used in Bayer names) | Geminorum |
| Zodiacal constellation | Yes |
| Ptolemaic constellation | Yes — one of Ptolemy’s 48 (Almagest VII–VIII) |
Constellations are not the same as the tropical signs: the signs are 30° divisions measured from the March equinox, while constellations are IAU sky regions of unequal size. Precession has moved the constellations roughly one sign-width against the tropical zodiac since antiquity.
Vault stars in Gemini
| Star | Designation | λ J2000.0 | λ 2026.0 | V mag |
|---|---|---|---|---|
| Tejat Prior | η Geminorum | 3°26′ Cancer | 3°48′ Cancer | 3.28 |
| Tejat Posterior | μ Geminorum | 5°18′ Cancer | 5°40′ Cancer | 2.87 |
| Alhena | γ Geminorum | 9°06′ Cancer | 9°28′ Cancer | 1.92 |
| Wasat | δ Geminorum | 18°31′ Cancer | 18°53′ Cancer | 3.53 |
| Castor | α Geminorum | 20°14′ Cancer | 20°36′ Cancer | 1.58 |
| Pollux | β Geminorum | 23°13′ Cancer | 23°34′ Cancer | 1.14 |
Sources
- IAU, The Constellations (88 official constellations, abbreviations): https://www.iau.org/public/themes/constellations/
- Swiss Ephemeris fixed-star catalogue
sefstars.txt(ICRS/Hipparcos-based positions, proper motions, magnitudes): https://github.com/aloistr/swisseph/blob/master/ephe/sefstars.txt — ecliptic longitudes computed for this vault with Astropy 8.0 (GeocentricMeanEcliptic, mean equinox of J2000.0 and of 2026-01-01) - Ptolemy, Almagest VII–VIII (star catalogue of 48 constellations), trans. G. J. Toomer (1984)