Sunspots and magnetism

Astronomers learned over centuries that sunspots appear in cycles, but deeper understanding came with the realization of their magnetic properties. Spectral analysis revealed that sunspots exhibited the Zeeman effect and were subjected to strong electromagnetic fields.
 George Ellery Hale United States 1908 Sunspots and magnetism

Astronomers learned over centuries that sunspots appear in cycles, but deeper understanding came with the realization of their magnetic properties. Spectral analysis revealed that sunspots exhibited the Zeeman effect and were subjected to strong electromagnetic fields.