Astronomy › Section K · The Sun › Topic K.2
The solar cycle
The Sun is not a perfect, unchanging ball. Dark spots come and go in a rhythm of about 11 years, and behind that rhythm lies the Sun's tangled, ever-changing magnetic field.
In this topic
- A Sun that changes
- What a sunspot is
- Worked example: how dark is a sunspot?
- Sunspots reveal the Sun's rotation
- Worked example: a spot riding the equator
- The sunspot cycle
- Measuring magnetism: the Zeeman effect
- A 22-year magnetic cycle
- The solar dynamo
- Solar Cycle 25, as of 2026
- Common mistakes to avoid
- Key takeaways
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