What is a pulsating star?

No expert has to tell us that most of the stars seem to vary, now brighter now dimmer, like flickering flames. Perhaps the official name for these sparklers is pulsating stars. Not so, say the experts. The antics of a true pulsating star are far more dramatic than a twinkling wink. The wondrous heavens are populated with a wide assortment of star types young and old, giants and dwarfs, fiery red and flaming gold, white hot and hotter blue white. Most stars are steady characters and constant by nature. As a rule, the astrophysicists can place a star in a certain class and expect it to stay there. The coolest stars are the m type red giants. The hottest are the 0 type blue white stars. Pulsating stars are odd balls of fire that refuse to abide by this neat system of grades and classes. When we use our eyes alone to estimate the brightest and the dimmest stars, we are estimating their apparent magnitudes. But objects seem to shrink and dish with distance, and this optical trick is true ...  more