We present the characterization of the Kepler-93 exoplanetary system , based on three years of photometry gathered by the Kepler  spacecraft .
The duration and cadence of the Kepler  observations , in tandem with the brightness of the star , enable unusually precise constraints on both the planet and its host .
We conduct an asteroseismic analysis of the Kepler  photometry and conclude that the star has an average density of 1.652 \pm 0.006 g cm ^ { -3 } .
Its mass of 0.911 \pm 0.033 M _ { \odot } renders it one of the lowest-mass subjects of asteroseismic study .
An analysis of the transit signature produced by the planet Kepler-93b , which appears with a period of 4.72673978 \pm 9.7 \times 10 ^ { -7 } days , returns a consistent but less precise measurement of the stellar density , 1.72 ^ { +0.02 } _ { -0.28 } g cm ^ { -3 } .
The agreement of these two values lends credence to the planetary interpretation of the transit signal .
The achromatic transit depth , as compared between Kepler  and the Spitzer  Space Telescope , supports the same conclusion .
We observed seven transits of Kepler-93b with Spitzer , three of which we conducted in a new observing mode .
The pointing strategy we employed to gather this subset of observations halved our uncertainty on the transit radius ratio R _ { P } / R _ { \star } .
We find , after folding together the stellar radius measurement of 0.919 \pm 0.011 R _ { \odot } with the transit depth , a best-fit value for the planetary radius of 1.481 \pm 0.019 R _ { \oplus } .
The uncertainty of 120 km on our measurement of the planet ’ s size currently renders it one of the most precisely measured planetary radii outside of the Solar System .
Together with the radius , the planetary mass of 3.8 \pm 1.5 M _ { \oplus } corresponds to a rocky density of 6.3 \pm 2.6 g cm ^ { -3 } .
After applying a prior on the plausible maximum densities of similarly-sized worlds between 1–1.5 R _ { \oplus } , we find that Kepler-93b possesses an average density within this group .