  People cannot witness the stellar evolution process of a single star
obviously in most cases because of its extremely secular time-scale, except for
some special time nodes in it (such as the supernova explosion). But in some
specific evolutionary phases, we have the chances to witness such process
gradually on human times-scales. When a star evolved leaving from the main
sequence, the hydrogen nuclei fusion in its core is gradually transferring into
the shell. In the Hertzsprung-Russell diagram, its evolutionary phase falls
into the Hertzsprung gap, which is one of the most rapidly evolving phases in
the life of a star. Here we report a discovery of a rapidly evolving
high-amplitude $\delta$ Scuti star KIC6382916 (J19480292+4146558) which is
crossing the Hertzsprung gap. According to the analysis of the archival data,
we find three independent pulsation modes of it, whose amplitudes and
frequencies are variating distinctly in 4 years. The period variation rates of
the three pulsation modes are one or two orders larger than the best seismic
model constructed by the standard evolution theory, which indicates the current
theory cannot precisely describe the evolution process in this rapidly evolving
phase and needs further upgrades. Moreover, the newly introduced Interaction
Diagram can help us to find the interactions between the three independent
pulsation modes and their harmonics/combinations, which opens a new window to
the future asteroseismology.
