Sunspots (Observed 27th November 2020)

Sunspots are dark patches that appear periodically on the Sun’s surface (on its photosphere). They appear dark because they are about 2000°C cooler than the surrounding photosphere. The spots are produced in regions where localised strong magnetic fields cause cooling by impeding the normal outward convection of energy from lower levels in the Sun’s interior.

Warning: Never look directly at the Sun as it can easily cause irreversible damage to the eye. You cannot see sunspots with the naked eye!!! The images here were taken with a black polymer solar filter sheet which transmits 1/1000th of the light passing through it, whilst images were taken digitally and observed on a laptop screen.

Above: The Sun, observed on 11th November 2019, just prior to the commencement of Solar Cycle 25.

The production of sunspots (and solar flares) reaches a maximum in terms of area and overall number at intervals of about 11 years. This is due to a cyclic variation in solar activity, known as the Solar Cycle – Every 11 years or so, the polarity pattern of magnetic regions on the Sun reverses, causing an increase in solar activity. Hence, the overall duration of the Solar Cycle itself is about 22 years and the Sunspot Cycle takes about 11 years.

Above: Sunspot activity as of 27th November, 2020. For comparison, the larger of the two “main” sunspots seen here (in an area classed as Region 2786) is about the same diameter as planet Earth.

Solar Cycle 25 technically began in December 2019, but as of November 2020 (when they were observed here), it was truly underway. This cycle is (at the time of writing) expected to peak with 115 sunspots in July 2025.
Sunspots occur in groups and have a dark centre (umbra) surrounded by a brighter border (penumbra). They can range from about 600 to 25,000 miles (1,000 to 40,000km) in diameter. Small spots may only last for a few hours, whilst larger ones may be visible for weeks and months.

A more detailed view of the sunspots observed on 27th November, 2020.

The spots travel from one side of the Sun’s disc to the other as the Sun rotates. This rotation, of about 27 days, was first detected by observing their motion; the Sun’s period of rotation varies from about 25 days near its equator to about 35 days near its poles and its axis of rotation is tilted by about 7.25 degrees.

References and Further Information

1. Sunspots on Wikipedia Here
2. Moore, P., 1987. The Astronomy Encyclopaedia. London: Mitchell Beazley.
3. Rees, M., 2005. Universe. London: Dorling Kindersley.

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