Kepler-21

At an apparent visual magnitude of 8.25 this was the brightest star observed by the Kepler spacecraft to host a validated planet until the discovery of an exoplanet orbiting HD 212657 in 2018.

[3][11] This system is located at a distance of 354 light-years (109 parsecs) from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −18.2 km/s.

[6] The spectrum of HD 179070 presents as an evolving F-type subgiant star with a stellar classification of F6 IV.

The star is radiating five times the luminosity of the Sun from its photosphere at an effective temperature of 6,305 K.[8] A faint nearby source was detected in 2011 and determined to be a co-moving stellar companion in 2016.

[9] A candidate transiting exoplanet was discovered based on data from the first four months of photometry from the Kepler spacecraft.