Earth and Space

Spotting sunspots

Stories from Physics for 11-14 14-16 IOP RESOURCES

  • There is evidence of observation of sunspots in ancient Greek and Chinese astronomical records. One of the earliest telescopic observations of the phenomenon was made by amateur father-and-son observers David and Johannes Fabricius in 1610. On David’s birthday, the pair noted dark spots on an image of the Sun projected through a telescope. Johannes published an essay on his discovery, preceding Galileo’s description of sunspots by a year. The pair did not survive to see the impact of their discovery - Johannes died four years later and his father was murdered shortly after by a farmer whom Fabricius had accused of stealing a goose.
  • Whilst to the Earth-based observer, sunspots look like small black spots on the surface of the Sun, their appearance is deceptive as they are perceived in relation to the Sun. Sunspots can have a diameter of up to 100,000 km and have temperatures of around 4,300 K. Seen in isolation, a sunspot would be around a hundred times as bright as the full Moon and only seem dim in comparison to the surrounding surface of the Sun.
  • The Sun’s magnetic field can reverse at times of maximum sunspot activity. In 2001, the solar magnetic field suffered such a change and the reversals are hypothesised to follow the 11-year cycle of sunspot activity.


Limit Less Campaign

Support our manifesto for change

The IOP wants to support young people to fulfil their potential by doing physics. Please sign the manifesto today so that we can show our politicians there is widespread support for improving equity and inclusion across the education sector.

Sign today