Psi Serpentis

Psi Serpentis (ψ Ser, ψ Serpentis) is a triple star system within the Serpens Caput part of the equatorial constellation Serpens. Based upon an annual parallax shift of 68.22 mas as seen from Earth, it is located approximately 47.8 light years from the Sun. This system came closest approach to the Sun about 585,000 years ago when it made perihelion passage at an estimated distance of 7.134 pc. Psi Serpentis is faintly visible to the naked eye with an apparent visual magnitude of 5.84.

This system can be resolved into two components that orbit each other with a period of 528.79 years and an eccentricity of 0.146. The primary, component A, is a yellow-hued G-type main sequence star with a stellar classification of G5 V. It is a solar analog, but its physical properties differ enough from the Sun to not be considered a solar twin. The star has an estimated 99.3% of the mass of the Sun, and it matches the Sun's radius within the margin of error. It is radiating 98% of the solar luminosity from its photosphere at an effective temperature of 5,683 K.

When observed from 1997 through 2000, the primary component appeared to be transitioning from a maunder minimum state to a state of cycling magnetic activity. It has developed a four-year activity cycle. During the period 2000–2004, it showed a strong activity cycle with little correlation between photometric variation and surface activity. This was followed by a flatter activity cycle from 2004 to 2008 that showed an inverse brightness variation with the level of activity. The difference in the two cycles may indicate a change from faculae-dominated to star spot-dominated variations in luminosity.

The known secondary, component B, is magnitude 12.00 and lies at an angular separation of 4.6 arc seconds from the primary along a position angle of 18°, as of 2013. In 2015, this component was resolved via interferometry into a binary star system with a separation of 0.22 arc seconds, corresponding to a projected separation of 3 AU. Both components, Ba and Bb, are likely red dwarfs roughly of class M3 with masses close to a quarter of that of the Sun. Their orbital period is estimated to be 6.57 years, and the eccentricity is moderately high, at 0.357. The orbit of Ba and Bb is not coplanar to their orbit around A.