Lambda Hydrae
λ Hydrae, Latinised as Lambda Hydrae, is a spectroscopic binary star in the constellation Hydra. Its apparent magnitude is 3.61 Located around 33.3 parsecs (109 ly) distant. The spiral galaxy NGC 3145 is only 7.8′ away to the southwest.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 10h 10m 35.27667s |
| Declination | −12° 21′ 14.6938″ |
| Apparent magnitude (V) | 3.61 |
| Characteristics | |
| Spectral type | K0IIIbCN0.5 |
| U−B color index | 0.92 |
| B−V color index | 1.00 |
| Astrometry | |
| Radial velocity (Rv) | 19.4 km/s |
| Proper motion (μ) | RA: -201.27 mas/yr Dec.: -99.63 mas/yr |
| Parallax (π) | 30.0232 ± 0.6973 mas |
| Distance | 109 ± 3 ly (33.3 ± 0.8 pc) |
| Absolute magnitude (MV) | +0.92 |
| Orbit | |
| Period (P) | 1585.8 days |
| Semi-major axis (a) | 16.79 mas |
| Eccentricity (e) | 0.138 |
| Inclination (i) | 79.49° |
| Longitude of the node (Ω) | 249.62° |
| Periastron epoch (T) | 2448664.3906 |
| Argument of periastron (ω) (secondary) | 238.9° |
| Details | |
| λ Hya A | |
| Mass | 1-2 M☉ |
| Radius | 9.7 R☉ |
| Luminosity | 39.8 L☉ |
| Surface gravity (log g) | 2.64 cgs |
| Temperature | 4,656 K |
| Metallicity [Fe/H] | +0.25 dex |
| Rotational velocity (v sin i) | 1.9 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary is an orange giant of spectral type K0IIICN+1, a star that has used up its core hydrogen, left the main sequence, and expanded into a giant. It is considered to be a red clump giant, a cool horizontal branch star that is burning helium in its core.
λ Hydrae has two visual companions, components B and C, 11th and 13th magnitude stars respectively 71″ and 111″ away.
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