This crossing slightly dims the star at a regular interval, which is used to determine if the cause of the fluctuation in brightness is indeed due to a planetary transit.

[3] The planet was first noted as a potential transit event by the Kepler telescope, and was originally designated as KOI 10.01.

Keck Observatory yielded additional information about the planet, including its mass and radius.

Its discovery, along with the planets Kepler-4b, Kepler-5b, Kepler-6b, and Kepler-7b, were announced to the public at the 215th meeting of the American Astronomical Society in Washington, D.C.

With a mass and radius of, respectively, 1.213 Msun and 1.486 Rsun, the star is both more massive and wider than the Sun.

With an effective temperature of 6213 K, Kepler-8 is also hotter than the Sun, although it is approximately three quarters of a billion years younger and is slightly less metal-rich.