The swirling green color is an image of the sun's atmosphere. This atmosphere, known as the corona, is a layer of intensely hot gas ranging from around 1.8 to 3.6 million degrees Fahrenheit. The corona, which is approximately 1.5 million degrees, doesn't actually look green to the naked eye — NASA's imagers simply assign the color green to images that are approximately 1.5 million degrees.

SOHO draws maps like this, corresponding to four different temperatures in the corona. By observing these temperatures, scientists watch the way in which the different streams of gas move around the sun. They can also track sudden changes in the corona, such as when a solar flare shoots out from the sun, sending a billion tons of matter traveling a million miles an hour in our direction. Luckily, these flares spread out to a harmless vacuum before they hit Earth, but the magnetic fields can still wreak havoc on our satellites.

This image could never be seen with the naked eye, because it's taken in ultraviolet light — the image comes from SOHO's Extreme ultraviolet Imaging Telescope (EIT). Different temperatures in the corona give off different wavelengths of ultraviolet light. In order to track the four separate temperatures of gas in the corona, the EIT is really just monitoring four separate wavelengths of UV rays.