Sunspot

• Large, dark features seen on the surface of the Sun
• Caused by increased magnetic activity
  • The magnetic field lines are twisting due to differential rotation
  • The twisting creates knots which show up as sunspots
• Cooler than the surrounding areas of the sun
  • ~3800 K vs. ~5800 K
  • Still hotter than the surface of many stars
• Consist of two spots
  • Umbra
    • Inner dark core
  • Penumbra
    • Surrounding less dark region
• Can become bigger than Earth

Sunspot Cycle

• Number of sunspots varies systematically
• Cycles every decade or so
• Sunspot maxima occur at an average interval of 11 year
  • More than 100 sunspots can be seen at once

Sun Astronomy