HD 9578 is a candidate wide binary star system located at a distance of approximately 183 light-years from the Sun in the southern constellation of Sculptor. The main star must be viewed with binoculars or a telescope, as its low apparent visual magnitude of 8.35 is too faint to be viewed with the naked eye. The system is drifting closer to the Sun with a radial velocity of −4 km/s.
The primary component is an ordinary G-type main-sequence star with a stellar classification of G1V. It is around five and a half billion years old, and is spinning with a projected rotational velocity of 2.4 km/s. The star has nearly the same mass as the Sun but with an 11% greater girth. It is radiating 1.4 times the luminosity of the Sun from its photosphere at an effective temperature of 5,798 K.
A faint co-moving companion was detected in 2015, located at an angular separation of along a position angle of from the primary, corresponding to a projected separation of . Designated component B, it is a red dwarf with a class of around M4 and has an estimated 0.21 times the mass of the Sun.
The discovery of a candidate extrasolar planetary companion was announced in a press release in October 2009, but although mentioned in one paper, it has not been published in a peer-reviewed journal, as noted by a 2017 study. Designated HD 9578 b, this object is thought to have at least 0.62 times the mass of Jupiter, and take 494disp=outNaNdisp=out to orbit the primary, with an orbital semimajor axis of 1.27 AU.[1]