  Inelastic neutron scattering is used to study the low-energy magnetic
excitations in the spin-1 triangular lattice of the 6H-B phase of
Ba$_3$NiSb$_2$O$_9$. We study two powder samples: Ba$_3$NiSb$_2$O$_9$
synthesized under high pressure and Ba$_{2.5}$Sr$_{0.5}$NiSb$_2$O$_9$ in which
chemical pressure stabilizes the 6H-B structure. The measured excitation
spectra show broad gapless and nondispersive continua at characteristic wave
vectors. Our data rules out most theoretical scenarios that have previously
been proposed for this phase, and we find that it is well described by an
exotic quantum spin liquid with three flavors of unpaired fermionic spinons,
forming a large spinon Fermi surface.
