Another set of cool – or rather warm – images were taken by another Solar Orbiter instrument called SPectral Imaging of the Coronal Environment (SPICE). This remote sensing instrument looks at the sun in the ultraviolet wavelength, seeing the different temperatures of different layers of the sun’s atmosphere.
“SPICE is designed to trace the layers of the Sun’s atmosphere from the corona, to a layer known as the chromosphere, approaching the surface. The instrument does this by examining the different wavelengths of extreme ultraviolet light from different atoms,” explains the ESA. “In the SPICE image sequence, purple corresponds to hydrogen gas at a temperature of 10,000°C, blue to carbon at 32,000°C, green to oxygen at 320,000°C, yellow neon at 630,000°C.”
While in most everyday situations you expect to find higher temperatures when approaching a hot object, the sun is not like that. The hottest part of the sun is actually its corona, which reaches 1,000,000°C, while its surface temperature is well below 5,000°C. This is one of the reasons why Solar Orbiter studies the solar corona, to understand how this huge difference in temperature occurs.
These readings using SPICE were taken on the same day as the EUI readings as the spacecraft passed the Sun-Earth line. This means they can be compared to readings taken by Earth-based instruments, to create a more complete picture of how changes in the sun propagate through the solar system.