1 Centauri
1 Centauri, or i Centauri, is a yellow-white hued binary star system in the southern constellation Centaurus. It can be seen with the naked eye, having an apparent visual magnitude of +4.23. Based upon an annual parallax shift of 51.54 mas as seen from Earth's orbit, it is located 51.5 light years from the Sun. The system is moving closer to the Sun with a radial velocity of −21.5 km/s.
Spectrographic images taken at the Cape Observatory between 1921 and 1923 showed this star has a variable radial velocity, which indicated this is a single-lined spectroscopic binary star system. The pair have an orbital period of 9.94 days and an eccentricity of about 0.2.
The primary component has received a number of different stellar classifications. For example, Jaschek et al. lists F0V, F2III, F4III, and F4IV, thus ranging in evolutionary state from an ordinary F-type main-sequence star to a giant star. More recently, Houk listed a class of F3 V, matching an ordinary main-sequence star that is generating energy through hydrogen fusion at its core. The NStars project gives it a classification of F2 V.
