It has a very high temperature of one to two million Kelvin.
We are able to see it during a solar eclipse, or by using a special device called the coronagraph. This is the rarefied upper atmosphere of the Sun. It is impossible to see the Corona with the naked eye, but there is an exception. It starts at about 1300 miles above the photosphere, and its temperature is measured to be around 900,000 degrees Fahrenheit. There are four outer layers of the Sun, and the Corona is the outermost one. The outer layers are the Corona, the Transition Region, the Chromosphere, and the Photosphere, while the inner layers are the Core, the Radiative Zone, and the Convection Zone.
The layers of the Sun are divided into two larger groups, the outer and the inner layers. The temperature should be even lower farther away from the Sun, but the temperature of the corona is measured at more than a million degrees. Even if the temperature in the core of the Sun does reach 15 million degrees, it drops to a mere 5000 degrees at the surface. However, we can determine the internal structure of the Sun, and it is made up of seven different layers. The problem is, no one can really explain how this corona exists. Because the Sun is mostly composed of helium and hydrogen and is not solid, it does not have an outer boundary that is clearly defined. The Suns corona is much hotter (by a factor from 150 to 450) than the visible surface of the Sun: the photospheres average temperature is around 5800kelvin. The critical difference is that the Sun is not solid, unlike Earth, so the layers are a bit harder to determine. Within these zones, dense loops of magnetized plasma are in. Researchers on the study put forth the case that heavier ions like silicon are given preferential treatment and get roasted in both the solar wind and the threshold region between the sun's chromosphere and corona. Just like our planet, and most other celestial bodies, the Sun is divided into distinct layers. Scientists get the low down on sun’s super hot atmosphere.