Red dwarf: Proxima Centauri on the right, next to its much brighter companionsDigitized Sky Survey 2/ Davide De Martin/Mahdi Zamani/ESOBy Ken CroswellThey’re a happy family after all. The three closest stars to the solar system all revolve around one another, astronomers say, resolving a century-long debate. The nearest of the three, Proxima Centauri,...