  Almost all massive stars explode as supernovae and form a black hole or
neutron star. The remnant mass and the impact of the chemical yield on
subsequent star formation and galactic evolution strongly depend on the
internal physics of the progenitor star, which is currently not well
understood. The theoretical uncertainties of stellar interiors accumulate with
stellar age, which is particularly pertinent for the blue supergiant phase.
Stellar oscillations represent a unique method of probing stellar interiors,
yet inference for blue supergiants is hampered by a dearth of observed
pulsation modes. Here we report the detection of diverse variability in blue
supergiants using the K2 and TESS space missions. The discovery of pulsation
modes or an entire spectrum of low-frequency gravity waves in these stars allow
us to map the evolution of hot massive stars towards the ends of their lives.
Future asteroseismic modelling will provide constraints on ages, core masses,
interior mixing, rotation and angular momentum transport. The discovery of
variability in blue supergiants is a step towards a data-driven empirical
calibration of theoretical evolution models for the most massive stars in the
Universe.
