  We show results from the radiation hydrodynamics (RHD) simulations of tidal
disruption of a star on a parabolic orbit by a supermassive black hole (SMBH)
based on a three-dimensional smoothed particle hydrodynamics code with
radiative transfer. We find that such a tidally disrupted star fragment and
form clumps soon after its tidal disruption. The fragmentation results from the
endothermic processes of ionization and dissociation that reduce the gas
pressure, leading to local gravitational collapse. Radiative cooling is less
effective because the stellar debris is still highly optically thick in such an
early time. Our simulations reveal that a solar-type star with a stellar
density profile of n=3 disrupted by a 10^6 solar mass black hole produces
$\sim20$ clumps of masses in the range of 0.1 to 12 Jupiter masses. The mass
fallback rate decays with time, with pronounced spikes from early to late time.
The spikes provide evidence for the clumps of the returning debris, while the
clumps on the unbound debris can be potentially freely-floating planets and
brown dwarfs. This ionization and dissociation induced fragmentation on a
tidally disrupted star are a promising candidate mechanism to form low-mass
stars to planets around an SMBH.
