  We report the discovery of ripple-like X-ray surface brightness oscillations
in the core of the Centaurus cluster of galaxies, found with 200 ks of Chandra
observations. The features are between 3 to 5 per cent variations in surface
brightness with a wavelength of around 9 kpc. If, as has been conjectured for
the Perseus cluster, these are sound waves generated by the repetitive
inflation of central radio bubbles, they represent around 5x10^42 erg/s of
spherical sound-wave power at a radius of 30 kpc. The period of the waves would
be 10^7 yr. If their power is dissipated in the core of the cluster, it would
balance much of the radiative cooling by X-ray emission, which is around
1.3x10^43 erg/s within the inner 30 kpc. The power of the sound waves would be
a factor of four smaller that the heating power of the central radio bubbles,
which means that energy is converted into sound waves efficiently.
