HD 21693

apparent visual magnitude of 7.94,^[2] therefore it is not visible to the naked eye. From its parallax measured by the Gaia spacecraft, it is located at a distance of 108.6 light-years (33.3 parsecs) from Earth.^[1]

spectral type of G9IV-V, with features intermediate between main sequence and subgiant. In 2011, the discovery of two Neptune-mass exoplanets

spectral type of G9IV-V,^[3] indicating it is a slightly evolved star that is between the main sequence and the subgiant branch. Stellar evolution models suggest that it is right at the end of the main sequence, on the hook before the subgiant turnoff,^[1] with a mass of 0.90 M_☉ and an age of around 7 billion years, although with a high uncertainty of plus or minus 4 billion years.^[5] From its Gaia-measured distance and brightness, it is calculated to have a radius of 0.93 R_☉ and a luminosity of 0.66 L_☉.^[1] Its effective temperature is 5,430 K and its metallicity, the proportion of elements heavier than helium, and approximately equal to that of the Sun.^[6]

chromospheric activity index varies between −5.02 and −4.83 during the cycle, an amplitude that is similar to that of the Sun's magnetic cycle. This index also shows a weaker variation with a period of 33.5 days, which may correspond to the star's rotation period. The activity cycle also affects the radial velocity of the star, which had to be taken into account when creating the orbital solution of the planets in the system.^[7]

arcseconds (16.7 AU).^[8]

residuals, after removing all periodic signals, still show higher variability than expected, which can be caused by strong granulation on the star's surface.^[7]

inclination of its orbit, the planet's true mass cannot be determined, although the true mass is usually close to the minimum value. This planet orbits the star at a distance of 0.15 AU with a period of 22.7 days.^[7]