Track and measure sunspots

How to find, follow and analyse these dynamic features on our ever-changing Sun

- Mary McIntyre

The Sun's surface often looks speckled with darker regions. These are sunspots – cooler patches that form as a result of the Sun's complex magnetic field preventing heat from reaching localised areas of the photosphere. How many you'll see varies during the 11-year solar cycle, with greater numbers during solar maximum – which we're in right now.

Humans have been observing sunspots for centuries, but we have only tracked them in detail since the telescope was invented. Originally, this meant projecting through the telescope onto a piece of white card and sketching the result. These days, observing and photographing the Sun is done either with a certified solar filter on the front of a telescope or a Herschel wedge on the back of a refractor.

Sunspots are related to intense magnetic activity and are often associated with solar flares and coronal mass ejections. These in turn are responsible for geomagnetic storms on Earth. While these produce stunning aurorae, they also impact spacecraft, satellites and infrastructure like the power grid, as well as the health of pilots and astronauts.

Check for spots

This is why solar activity is monitored constantly, not just by ground-based observations here on Earth but also via satellites such as the Solar Dynamics Observatory (SDO). The multi-wavelength images that the SDO creates are freely available to download, so you can measure, track and analyse sunspots even if you don't have a telescope.