  The CoO$_{2}$ layers in sodium-cobaltates Na$_{x}$CoO$_{2}$ may be viewed as
a spin $S=1/2$ triangular-lattice doped with charge carriers. The underlying
physics of the cobaltates is very similar to that of the high $T_{c}$ cuprates.
We will present unequivocal $^{59}$Co NMR evidence that below $T_{CO}\sim51 K$,
the insulating ground state of the itinerant antiferromagnet
Na$_{0.5}$CoO$_{2}$ ($T_{N}\sim 86 K$) is induced by charge ordering.
