Then, astronomers began to use the spectroscopic data from a few stars to model the variability of certain spectral lines that in the Sun correlate with the sizes of sunspots. These models often showed large starspots covering the stars, and as the star rotates, the spectral lines vary as the spots move across the face of the star from our vantage point. This is important research because we know that during the 'Little Ice Age' in Europe about 300 years ago, there were few reports of sunspots, and then suddenly the 11 year cycle started up at the end of this period. By studying other stars and their sunspot activity we can better understand the mechanism that produces them, and how it changes over long periods of time. Starspots also seem to occur on neutron stars.
Neutron stars have powerful magnetic fields.
Matter can flow down these field lines from great distances, and when it crashes onto the neutron star's surface, it produces a hot spot which emits enormous quantities of x-ray and gamma ray energy. Instead of these starspots being darker than the surrounding material, they are luminous beacons of energy. Dr. Sten Odenwald Return to Ask the Astronomer .