Labels:text | screenshot OCR: VARIABLE STARS VARIABLE STARS vary in brightness, whether regularly or irregularly. Cataclysmic variables, such as novas Cepheid-variable or supernovas, suddenly become many star thousands of times brighter because of a violent outburst of energy. Pulsating variables, many of which are huge red giants, swell and contract regularly, dimming and brightening in time with their pulses. Cataclysmic and pulsating variables vary in both true brightness and apparent brightness. Eclipsing binary stars, however, vary in only apparent brightness; this occurs when STELLAR PULSE one star passes in front of the other and Pulsating stars have an unstable structure that causes blocks light traveling from it to Earth. them regularly to pulsate. DISTANCE INDICATORS
