One graph attempts to connect every object in the universe

If you've ever taken an introductory astronomy class, you've probably seen the Hertzsprung-Russell (HR) diagram. This graph maps out the life cycle of stars by plotting their temperature against their luminosity, and has been a "cheat sheet" for stellar astrophysics for over a century. But the universe is full of more than just stars, and a new paper in the journal Publications of the Astronomical Society of the Pacific by Gabriel Steward and Matthew Hedman of the University of I...