  We investigated the doubly bottom molecule state $T^-_{bb}$ composed of two
bottomed mesons. The potentials are obtained by using the one-boson-exchange
model. With the heavy quark flavor symmetry, all the parameters in the model
are determined from the doubly charmed tetraquark $T_{cc}^{+}$ by fitting its
experimental data in our previous work. The mass of the bound state is
predicted to be around $10560$ MeV ($\approx 44$ MeV below the
$\bar{B}\bar{B}^*$ threshold), which is consistent with the lattice
calculations. Furthermore, a resonance state around $10621$ MeV was found.
These results, extracted by using the complex scaling method and $T$-matrix,
are remarkably consistent with each other. The $\bar{B}\bar{B}^*$ molecule
predicted here could be observed in the electromagnetic decay channel
$\bar{B}\bar{B}\gamma$, while the strong decay into $\bar{B}\bar{B}\pi$ channel
is forbidden. This research will help guide the search of these exotic states
in the future experiments and eventually deepen the insights of them.
