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Knowing the high-energy radiation environment of a star over a planet'sformation and evolutionary period is critical in determining if that planet ispotentially habitable and if any biosignatures could be detected, as UVradiation can severely change or destroy a planet's atmosphere. Current effortsfor finding a potentially habitable planet are focused on M stars, yet K starsmay offer more habitable conditions due to decreased stellar activity and moredistant and wider habitable zones (HZ). While M star activity evolution hasbeen observed photometrically and spectroscopically, there has been nodedicated investigation of K-star UV evolution. We present the firstcomprehensive study of the near-UV, far-UV, and X-ray evolution of K stars. Weused members of young moving groups and clusters ranging in age from 10 - 625Myr combined with field stars and their archived GALEX UV and ROSAT X-ray datato determine how the UV and X-ray radiation evolve. We find that the UV andX-ray flux incident on a HZ planet is 5 - 50 times lower than that of HZplanets around early-M stars and 50 - 1000 times lower than those around late-Mstars, due to both an intrinsic decrease in K dwarf stellar activity occurringearlier than for M dwarfs and the more distant location of the K dwarf HZ.

HAZMAT. V. The Ultraviolet and X-ray Evolution of K Stars