The Sun’s magnetic field goes through an 11-year cycle. When it is most active, plasma pouring out of the Sun into the solar wind can strike the Earth’s magnetic field and set off a cascade of issues for us here below, ranging from glorious auroras to problems with radio, cellphone, and electrical power transmissions.

Since 2006, a pair of Nasa satellites called “Stereo” have been orbiting the Sun, ahead and behind the Earth, monitoring this solar weather. Their cameras record the Sun’s corona, the thin crown of light around the Sun most memorable as that glow around the Moon during a total solar eclipse.

But “space” is not completely empty. The dust orbiting between the Sun and us scatters more sunlight than the light from the corona itself. Thus scientists monitoring the Sun have developed a number of clever techniques to subtract away the light from the dust and make the corona more visible.