Photographs of sunspots taken with the Kew Photoheliograph

Tracking sunspots

These photographs are from a series taken in September 1870 with the Kew Photoheliograph, the large instrument at the very right of this showcase. Astronomers used it to take daily photographs of the Sun. Comparing the photographs day by day showed how features such as sunspots moved. We now know these dark spots are caused by magnetic activity on the Sun’s surface.