Imagine what our night sky would look like if its stellar density was a million times greater than it is now. Remarkably, such places actually exist: They’re called “Ultracompact Dwarfs,” and astronomers are calling them an entirely new kind of galaxy. Undergraduate astronomy students Michael Sandoval and Richard Vo from San José University discovered a pair of record-breaking compact galaxies buried within data contained in the Sloan Digital Sky Survey. These exotic objects are similar to ordinary globular clusters, but upwards of a hundred to a thousand times brighter. Advertisement Image: The two ultra-dense compact galaxies were discovered orbiting...