Space Print from NASA: Solar Disc with Sunspots. Sunspots are relatively cool areas on the Sun's surface, the photosphere. Their temperature is about 3800 degrees Kelvin, as opposed around 5800 degrees on the rest of the photosphere, and they can measure as much as 50,000 km across (NASA Media Archives). Buy this picture as an unframed print or poster, a framed print or a mounted box canvas print.