HAYDN -- High-precision AsteroseismologY of DeNse stellar fields (ESA
  Voyage 2050 White Paper)
  In the last decade, the Kepler and CoRoT space-photometry missions have
demonstrated the potential of asteroseismology as a novel, versatile and
powerful tool to perform exquisite tests of stellar physics, and to enable
precise and accurate characterisations of stellar properties, with impact on
both exoplanetary and Galactic astrophysics. Based on our improved
understanding of the strengths and limitations of such a tool, we argue for a
new small/medium space mission dedicated to gathering high-precision,
high-cadence, long photometric series in dense stellar fields. Such a mission
will lead to breakthroughs in stellar astrophysics, especially in the metal
poor regime, will elucidate the evolution and formation of open and globular
clusters, and aid our understanding of the assembly history and chemodynamics
of the Milky Way's bulge and few nearby dwarf galaxies.
