1843 – Germany
‘The number of visible sunspots varies in a regular cycle that averages about 11 years’
GALILEO was the first to study sunspots. Schwabe made careful records of sunspots almost daily for 17 years before announcing his theory. He continued his observations for another 25 years.
Wherever magnetic fields emerge from the Sun, they suppress the flow of surrounding hot gases, creating relatively cool regions that appear as dark patches in the Sun’s shallow outer layer, the photosphere.
Sunspots vary in size from 1000 to 40,000 kilometres across and may last from a few days to many months.
Near a solar minimum there are only a few sunspots. During a solar maximum, solar flares can produce dramatic changes in the emission of ultraviolet rays and X-rays from the Sun.
TIMELINE
A History of Science 