A comparison of dwarf galaxies spanning a range of six orders of magnitude in stellar mass, decreasing from left to right and from top to bottom. The Large Magellanic Cloud, WLM and Pegasus are irregular dwarf galaxies that still contain gas and continue to form new stars. The remaining six have lost their gas and no longer show any star formation. The faintest galaxies in the image can only be detected in the vicinity of the Milky Way. Among them are Eridanus II and Pictoris I, two ultra-faint galaxies of particular relevance to this study. Image credits: Eckhard Slawik (LMC); ESO/Digitised Sky Survey 2 (Fornax); Massey et al. (2007; WLM, Pegasus and Phoenix); ESO (Sculptor); Mischa Schirmer (Draco); Vasily Belokurov and Sergey Koposov (Eridanus II and Pictoris I). Composition: Bullock & Boylan-Kolchin (2017).
