Humans are not alone in their struggle against an increasing waistline. Astronomers believe that galaxies too put on weight throughout their lives, growing not only by consuming hydrogen gas—which is then converted to stars—but also by cannibalizing other galaxies. It’s a galaxy-eat-galaxy cosmos, but the big surprise is that many galaxies seem to be growing to even larger sizes than their eating habits would suggest.
The gluttonous galaxies in question are known, perhaps not surprisingly, as “ellipticals.” Their three-dimensional form distinguishes them from disk-like galaxies, including slim and beautiful spirals like M51 and our own Milky Way. Ellipticals have long been known to be, well, fat.