  The discovery and characterization of exoplanets around nearby stars is
driven by profound scientific questions about the uniqueness of Earth and our
Solar System, and the conditions under which life could exist elsewhere in our
Galaxy. Doppler spectroscopy, or the radial velocity (RV) technique, has been
used extensively to identify hundreds of exoplanets, but with notable
challenges in detecting terrestrial mass planets orbiting within habitable
zones. We describe infrared RV spectroscopy at the 10 m Hobby-Eberly telescope
that leverages a 30 GHz electro-optic laser frequency comb with nanophotonic
supercontinuum to calibrate the Habitable Zone Planet Finder spectrograph.
Demonstrated instrument precision <10 cm/s and stellar RVs approaching 1 m/s
open the path to discovery and confirmation of habitable zone planets around
M-dwarfs, the most ubiquitous type of stars in our Galaxy.
