Three Small Planets Transiting a Hyades Star

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 $7.9757\pm 0.0011$, $17.30681_{-0.00036}^{+0.00034}$, and $25.5715_{-0.0040}^{+0.0038}$ days, and radii of $1.05\pm 0.16$, $3.14 \pm 0.36$,and$1.55^{+0.24}_{-0.21}$ $R_{\oplus }$, 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.