Magnitude 4.34 | Constellation Hydra | |
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Rho Hydrae (ρ Hya) 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. This system forms part of the ring-shaped asterism that represents the head of the hydra constellation. 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 factor of 0.06, due to intervening dust.
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.