  Fermi has discovered two giant gamma-ray-emitting bubbles that extend nearly
10kpc in diameter north and south of the galactic center (GC). The existence of
the bubbles was first evidenced in X-rays detected by ROSAT and later WMAP
detected an excess of radio signals at the location of the gamma-ray bubbles.
We propose that periodic star capture processes by the galactic supermassive
black hole, Sgr A$^*$, with a capture rate $3\times 10^{-5}$yr$^{-1}$ and
energy release $\sim 3\times 10^{52}$erg per capture can produce very hot
plasma $\sim 10$keV with a wind velocity $\sim 10^8$cm/s injected into the halo
and heat up the halo gas to $\sim 1$keV, which produces thermal X-rays. The
periodic injection of hot plasma can produce shocks in the halo and accelerate
electrons to $\sim$TeV, which produce radio emission via synchrotron radiation,
and gamma-rays via inverse Compton scattering with the relic and the galactic
soft photons.
