Eta Geminorum
 Location of η Geminorum (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Gemini |
| A | |
| Right ascension | 06h 14m 52.657s |
| Declination | +22° 30′ 24.48″ |
| Apparent magnitude (V) | 3.15 - 3.90 |
| B | |
| Right ascension | 06h 14m 52.569s |
| Declination | +22° 30′ 24.31″ |
| Apparent magnitude (V) | 6.04 |
| Characteristics | |
| Spectral type | M2 IIIa + G0 III |
| Variable type | SRa + EA |
| Astrometry | |
| Proper motion (μ) |
RA: −62.46 ± 1.06 mas/yr Dec.: −12.12 ± 0.70 mas/yr |
| Parallax (π) | 8.48 ± 1.23mas |
| Distance | approx. 380 ly (approx. 120 pc) |
| Absolute magnitude (MV) | −1.87 |
| Orbit | |
| Primary | Aa |
| Companion | Ab |
| Period (P) | 8.17 yr |
| Semi-major axis (a) | 0.077" |
| Eccentricity (e) | 0.53 |
| Orbit | |
| Primary | A |
| Companion | B |
| Period (P) | 473.7 yr |
| Semi-major axis (a) | 1.08" |
| Eccentricity (e) | 0.54 |
| Details | |
| Aa | |
| Mass | 6.30 M☉ |
| Radius | 153 R☉ |
| Luminosity | 3,162 L☉ |
| Temperature | 3,548 K |
| Metallicity [Fe/H] | +0.04 dex |
| Ab | |
| Mass | 2.06 M☉ |
| B | |
| Mass | 1.18 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta Geminorum (η Geminorum, abbreviated Eta Gem, η Gem), also named Propus, is a triple star system in the constellation of Gemini. It is a naked-eye variable star around 380 light years from the Sun.
Beta Geminorum is the star's Bayer designation. The traditional names Tejat Prior, Propus (from the Greek, meaning forward foot) and Praepes and Pish Pai (from the Persian Pīshpāy, پیشپای, meaning foreleg). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Propus for this star.
This star, along with γ Gem (Alhena), μ Gem (Tejat Posterior), ν Gem and ξ Gem (Alzirr) were Al Han'ah, "the brand" (on the neck of the camel). They also were associated in Al Nuḥātai, the dual form of Al Nuḥāt, "a Camel's Hump".
In Chinese lunar mansion, Tejat Prior is the only member of the lunar mansion 钺 (Pinyin: Yuè, Chinese 'Battle Axe').
η Geminorum lies at the foot of the Castor side of Gemini, about two degrees west of μ Geminorum and two degrees southeast of the bright open cluster M35. Between the two stars are several faint areas of nebulosity. η Gem just to the west of the supernova remnant shell IC 443. Further east around μ Gem is the emission nebula S249. In between is the small faint emission nebula IC 444 around the 7th magnitude 12 Geminorum.
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