  We report the detection of gravity modes in RR Lyrae stars. Thanks to PAIX,
the first Antarctica polar photometer. Unprecedented and uninterrupted U BV RI
time-series photometric ground-based data are collected during 150 days from
the highest plateau of Antarctica. PAIX light curve analyses reveal an even
richer power spectrum with mixed modes in RR Lyrae stars. A nonlinear nature of
several dominant peaks, showing lower and higher frequencies, occur around the
dominant fundamental radial pressure mode. These lower frequencies and
harmonics linearly interact with the dominant fundamental radial pressure mode
and its second and third overtone pressure modes as well. Half-integer
frequencies are also detected, likewise side peak structures demonstrating that
HH puppis is a bona-fide Blazhko star. Fourier correlations are used to derive
underlying physical characteristics for HH puppis. The most striking finding is
the direct detection of gravity waves. We interpret the excitation mechanism of
gravity waves in RR Lyrae stars by the penetrative convection driving
mechanism. We demonstrate that RR Lyrae stars pulsation is excited by several
distinct mechanisms, and hence RR Lyrae stars are simultaneously g modes and p
modes pulsators. Our discoveries make RR Lyrae stars very challenging stellar
objects, and provide their potential to undergo at the same time g modes and p
modes towards an advancement of theory of stellar evolution and a better
understanding of the Universe.
