• The equivalent of sunspots on stars other than the Sun. Spots are suspected of existing on variable stars whose brightness dips as they turn comparatively spotted faces towards Earth. By analogy with the Sun, where sunspots are associated with strong magnetism, starspots would indicate strong magnetic fields for the stars in question. Starspots covering a quarter of the surface of Proxima Centauri have been detected by the Hubble Space Telescope, accounting for a 41-day variability in its output.