KIC 10001893 is one out of 19 subdwarf-B ( sdB ) pulsators observed by the Kepler spacecraft in its primary mission .
In addition to tens of pulsation frequencies in the g -mode domain , its Fourier spectrum shows three weak peaks at very low frequencies , which is too low to be explained in terms of g modes .
The most convincing explanation is that we are seeing the orbital modulation of three Earth-size planets ( or planetary remnants ) in very tight orbits , which are illuminated by the strong stellar radiation .
The orbital periods are P _ { 1 } =5.273 , P _ { 2 } =7.807 , and P _ { 3 } =19.48 hours , and the period ratios P _ { 2 } /P _ { 1 } =1.481 and P _ { 3 } /P _ { 2 } =2.495 are very close to the 3:2 and 5:2 resonances , respectively .
One of the main pulsation modes of the star at 210.68 \mu Hz corresponds to the third harmonic of the orbital frequency of the inner planet , suggesting that we see , for the first time in an sdB star , g -mode pulsations tidally excited by a planetary companion .
The extreme planetary system that emerges from the Kepler data is very similar to the recent discovery of two Earth-size planets orbiting the sdB pulsator KIC 05807616 \citep charpinet11a .