Eta Geminorum
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Gemini |
| A | |
| Right ascension | 06h 14m 52.657s |
| Declination | +22° 30′ 24.48″ |
| Apparent magnitude (V) | 3.1 – 3.7 |
| B | |
| Right ascension | 06h 14m 52.569s |
| Declination | +22° 30′ 24.31″ |
| Apparent magnitude (V) | 6.04 |
| Characteristics | |
| Spectral type | M2 IIIa (Aa) A (Ab) G0 III (B) |
| Variable type | SRa + EA |
| Astrometry | |
| Proper motion (μ) | RA: −59.530±1.450 mas/yr Dec.: −7.766±1.385 mas/yr |
| Parallax (π) | 8.48±1.23 mas |
| Distance | approx. 380 ly (approx. 120 pc) |
| Absolute magnitude (MV) | −1.87 |
| Orbit | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 8.161 yr |
| Semi-major axis (a) | 0.077″ |
| Eccentricity (e) | 0.5507 |
| Periastron epoch (T) | JD 2444489.1 |
| Argument of periastron (ω) (primary) | 174.20° |
| Semi-amplitude (K1) (primary) | 9.438 km/s |
| Orbit | |
| Primary | A |
| Name | B |
| Period (P) | 473.7 yr |
| Semi-major axis (a) | 1.08″ |
| Eccentricity (e) | 0.54 |
| Details | |
| Aa | |
| Mass | 5.1 M☉ |
| Radius | 153 R☉ |
| Luminosity | 3,162 L☉ |
| Temperature | 3,502 K |
| Metallicity [Fe/H] | +0.04 dex |
| Age | 0.81 Gyr |
| Ab | |
| Mass | 2 M☉ |
| Radius | 1.65 R☉ |
| Luminosity | 16 L☉ |
| Temperature | 9,000 K |
| Other designations | |
| Propus, Praepes, Tejat Prior, Pish Pai, η Geminorum, 7 Geminorum, HD 42995, HR 2216, BD+22°1241, HIP 29655, SAO 78135, CCDM J06149+2230, ADS 4841 | |
| Database references | |
| SIMBAD | data |
Eta Geminorum (η Geminorum, abbreviated Eta Gem, η Gem), formally named Propus /ˈproʊpəs/, is a triple star system in the constellation of Gemini. It is a variable star visible to the naked eye, around 380 light years from the Sun. The position of this system near the ecliptic means it is subject to lunar occultation.