Science & history · An active star
The Sun's eleven-year cycle
The Sun's activity rises and falls on a cycle of about 11 years, and at each peak its magnetic poles swap places.
The cycle
About every 11 years the Sun's magnetic poles change polarity. Sunspot numbers, flares and eruptions rise towards solar maximum and fall towards minimum. Samuel Heinrich Schwabe found the cycle in 1843.
A peak known only afterwards
On 15 October 2024 NASA, NOAA and the international Solar Cycle Prediction Panel announced that the Sun had reached its maximum period. NOAA added that the month of the peak itself would not be identified for months or years: a maximum can only be dated once activity has clearly declined.
Sources
- NASA Sun: Facts (opens in a new tab) for age, size, distance, temperatures, layers, rotation, cycle, type, future · checked 2 October 2026
- NASA History Spots, Waves and Wind: A Solar Science Timeline (opens in a new tab) for Galileo 1613, Fraunhofer 1817, Schwabe 1843, Carrington 1859, Janssen 1868, Hale 1908, coronagraph 1931, Parker 1958, Maunder minimum · checked 2 October 2026
- NASA and NOAA Sun Reaches Maximum Phase in 11-Year Solar Cycle (15 October 2024) (opens in a new tab) for solar maximum announced; the peak month is identified only in hindsight; May 2024 storm · checked 2 October 2026