All stars appear to twinkle due to our ever-turbulent atmosphere. But some truly do rise and fall in brightness. These so-called variable stars seem to pulsate — either because a star is in a binary system and its companion often eclipses it, or because the star itself periodically swells and shrinks, pulsating in brightness. Polaris, the north star known for being so constant, is itself a variable star.
Sky & Telescope can help you monitor these dancing stars, providing valuable research to astronomy. For more than a century amateur astronomers have helped scientists monitor these stars, collecting nearly all the brightness data on record for hundreds of variable stars.