Rho Hydrae
Rho Hydrae, equally written ρ Hydrae, is a binary star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.34. The distance to this system, based upon an annual parallax shift of 9.21 mas, is about 354 light years. At that distance, the visual magnitude is diminished by an interstellar extinction of 0.06 magnitudes, due to intervening dust.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 08h 48m 25.97057s |
| Declination | +05° 50′ 16.1283″ |
| Apparent magnitude (V) | 4.34 |
| Characteristics | |
| Spectral type | A0 Vn |
| U−B color index | −0.04 |
| B−V color index | −0.04 |
| Astrometry | |
| Radial velocity (Rv) | +32.8 km/s |
| Proper motion (μ) | RA: −17.33 mas/yr Dec.: −29.41 mas/yr |
| Parallax (π) | 9.21 ± 0.21 mas |
| Distance | 354 ± 8 ly (109 ± 2 pc) |
| Absolute magnitude (MV) | −0.83 |
| Details | |
| Mass | 3.24±0.05 M☉ |
| Radius | 2.0 R☉ |
| Luminosity | 242 L☉ |
| Temperature | 9,795 K |
| Rotational velocity (v sin i) | 128 km/s |
| Age | 350 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary component is an A-type main sequence star with a stellar classification of A0 Vn. It has around double the radius of the Sun and 3.2 times the Sun's mass. Rho Hydrae is around 350 million years old and has a high rate of spin, with a projected rotational velocity of 128 km/s. It radiates 242 times the solar luminosity from its outer atmosphere at an effective temperature of 9,795 K. The companion is a magnitude 11.9 star at an angular separation of 12.1 arc seconds along a position angle of 146°, as of 2000.