HD 42618

HD 42618 is a well-studied^[7] star with an exoplanetary companion in the equatorial constellation of Orion. With an apparent visual magnitude of 6.85^[1] it is too faint to be readily visible to the naked eye. This system is located at a distance of 79.6 light years from the Sun based on parallax measurements. It has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.321″ per year.^[9] HD 42618 is drifting closer with a radial velocity of −53.5^[4] km/s and is predicted to come as near as 42.6 light-years in around 297,000 years.^[1]

The stellar classification of HD 42618 is G4V,^[3] which shows it to be an ordinary G-type main-sequence star. It is considered a close solar analog, which means the physical properties of the star are particularly similar to those of the Sun.^[10] Seismic model indicates the star is older and more evolved than the Sun with an age of about 5.5 billion years.^[5] It is spinning with a low projected rotational velocity of 1.8 km/s,^[6] with the rotation rate being consistent with the star's low activity level.^[11] The star has 92% of the mass of the Sun and 94% of the Sun's radius. The surface metallicity is lower than in the Sun,^[5] with the abundance patterns being consistent with a solar-type star.^[11] HD 42618 is radiating 92% of the luminosity of the Sun from its photosphere at an effective temperature of 5,765 K.^[5]

In 2016, the discovery of a candidate exoplanet companion orbiting HD 42618 was announced. Designated HD 42618 b, it was found using the radial velocity method which showed a periodicity of 149.6 days. The orbital elements have the planet orbiting at a distance of 0.55 AU from the host star with an orbital eccentricity (ovalness) of 0.2 and a Neptune-like mass. A second signal with a period of 388 days was detected, but this is unconfirmed and may be false. A 4,850 day signal is likely the result of star's magnetic activity cycle.^[7]