41 Herculis

The spectrum of 41 Herculis matches a spectral class of G8.^[5] Stellar evolution models suggest it is an evolved star that is in the base of the red-giant branch.^[2][16] The star is estimated to be six billion years old, has 1.15 times the mass of the Sun and 2.91 times the Sun's radius. It radiates 5.5 times the Sun's luminosity from its photosphere^[8] at an effective temperature of 5,077 K.^[9] This temperature give it the yellow hue typical of a G-type star.^[17]

41 Herculis has a common proper motion companion named Ross 643^[7] which is separated by 163.1" from the primary,^[4] yielding a projected separation of 7,150 au at the system's distance.^[7] It has a spectral type K3,^[5] has 0.65 times the mass of the Sun and 61% of the Sun's radius. It irradiates 18.2% of the Sun's luminosity from its photosphere at an effective temperature of 4,641 K,^[11] giving it an orange hue typical of K-type stars.^[17]

In 2026, a likely planet was discovered around the primary, from the detection of its gravitational pull in the discrepancy between the Hipparcos and Gaia proper motion measurements, taken over a 25-year baseline. Direct imaging and radial velocity data were used to constrain the orbit and mass of the planet, although the use of radial velocity and astrometry alone was enough to rule out stellar companions as the cause of the proper motion changes. The planet has an orbital period between 14.4 and 17.7 years, a semi-major axis of 6.4+0.6
−0.3 au and a mass of 9.5+5.4
−2.2 M_J. The mass constraint yields a 35% chance that it may be a brown dwarf rather than a planet.^[7]