We present the discovery of three small planets transiting K2-136 ( LP 358 348 , EPIC 247589423 ) , a late K dwarf in the Hyades .
The planets have orbital periods of 7.9757 \pm 0.0011 , 17.30681 ^ { +0.00034 } _ { -0.00036 } , and 25.5715 ^ { +0.0038 } _ { -0.0040 } days , and radii of 1.05 \pm 0.16 , 3.14 \pm 0.36 , and 1.55 ^ { +0.24 } _ { -0.21 } R _ { \earth } , respectively .
With an age of 600-800 Myr , these planets are some of the smallest and youngest transiting planets known .
Due to the relatively bright ( J=9.1 ) host star , the planets are compelling targets for future characterization via radial velocity mass measurements and transmission spectroscopy .
As the first known star with multiple transiting planets in a cluster , the system should be helpful for testing theories of planet formation and migration .