Sunspots

• A Sunspot is a temporary dark area that appears on the Sun’s surface and can last for between a few days to a few months.
• They are caused by intense magnetic activity and are often accompanied by solar flares and ejections of coronal mass.

History of Observation of Sunspots

• In 364 BCE Gan De
  • The first Sunspot to be recorded was in China by Gan De in his Star Catalogue.
• Theophrastus (371-287 BCE)
  • A Greek Astronomer, mentioned Sunspots.
• Ptolemy (c.90-c.168 CE)
  • He projected the Sun’s image onto a screen, and was able to observe the Sunspots. By watching the movement of the Sunspots, Ptolemy was able to observe the rotation of the Sun.

Sunspot Cycles

• Sunspots occur in Cycles of roughly 11.04 years, with some cycles varying between 8 to 14 years.
• A Sunspot at the Sun’s Equator takes 24.47 days to rotate around the Sun and appear in the same position. (Sidereal rotational period).
• At the Poles the rotational period is 38 days. This is because the Sun is a Gas not a Solid, it rotates differentially.