Rho Hydrae
Binary star in the constellation Hydra / From Wikipedia, the free encyclopedia
Rho Hydrae, equally written ρ Hydrae, is a binary star[9] in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.34.[2] The distance to this system, based upon an annual parallax shift of 9.21 mas,[1] 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.[7]
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 08h 48m 25.97057s[1] |
Declination | +05° 50′ 16.1283″[1] |
Apparent magnitude (V) | 4.34[2] |
Characteristics | |
Spectral type | A0 Vn[3] |
U−B color index | −0.04[2] |
B−V color index | −0.04[2] |
Astrometry | |
Radial velocity (Rv) | +32.8[4] km/s |
Proper motion (μ) | RA: −17.33[1] mas/yr Dec.: −29.41[1] mas/yr |
Parallax (π) | 9.21 ± 0.21 mas[1] |
Distance | 354 ± 8 ly (109 ± 2 pc) |
Absolute magnitude (MV) | −0.83[5] |
Details[3] | |
Mass | 3.24±0.05 M☉ |
Radius | 2.0[6] R☉ |
Luminosity | 242 L☉ |
Temperature | 9,795 K |
Rotational velocity (v sin i) | 128 km/s |
Age | 350[7] Myr |
Other designations | |
Database references | |
SIMBAD | data |
The primary component is an A-type main sequence star with a stellar classification of A0 Vn.[3] It has around double[6] the radius of the Sun and 3.2 times the Sun's mass. Rho Hydrae is around 350 million years old[7] 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.[3] 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.[10]