  Observations from the Kepler mission have revealed frequent superflares on
young and active solar-like stars. Superflares result from the large-scale
restructuring of stellar magnetic fields, and are associated with the eruption
of coronal material (a coronal mass ejection, or CME) and energy release that
can be orders of magnitude greater than those observed in the largest solar
flares. These catastrophic events, if frequent, can significantly impact the
potential habitability of terrestrial exoplanets through atmospheric erosion or
intense radiation exposure at the surface. We present results from numerical
modeling designed to understand how an eruptive superflare from a young
solar-type star, $\kappa^{1}Cet$, could occur and would impact its astrospheric
environment. Our data-inspired, three-dimensional magnetohydrodynamic modeling
shows that global-scale shear concentrated near the radial-field polarity
inversion line can energize the closed-field stellar corona sufficiently to
power a global, eruptive superflare that releases approximately the same energy
as the extreme 1859 Carrington event from the Sun. We examine proxy measures of
synthetic emission during the flare and estimate the observational signatures
of our CME-driven shock, both of which could have extreme space-weather impacts
on the habitability of any Earth-like exoplanets. We also speculate that the
observed 1986 Robinson-Bopp superflare from $\kappa^{1}Cet$ was perhaps as
extreme for that star as the Carrington flare was for the Sun.
