The regular expansion and contraction of a star's outer layers, causing periodic changes in brightness, temperature, and size. This stellar breathing occurs when the star's internal structure becomes unstable to radial oscillations.
From Latin 'pulsare' meaning 'to beat' or 'to strike repeatedly', related to 'pulse'. Applied to astronomy in the late 19th century when astronomers first observed regular brightness variations in certain stars.
Stellar pulsations turn stars into cosmic musical instruments, with some stars ringing like bells with multiple frequencies simultaneously! Asteroseismology uses these stellar vibrations to peer inside stars just like geologists use earthquakes to study Earth's interior, revealing the hidden structure of stellar cores.
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