The stellar atmosphere is divided into several layers:
The photosphere is the lowest and coolest layer of the stellar atmosphere.[1] The Sun's photosphere has a temperature of 5,770 K to 5,780 K.[1]
The chromosphere is the next layer after the photosphere. The chromosphere is above the photosphere. Its about 10 times the temperature of the photosphere.
The transition region is the next layer after the chromosphere. It is hotter than the chromosphere.[2]
The outermost part of the stellar atmosphere is the corona. It has a temperature of 1,000,000 K.[3] It seems that only some giant stars, and very few supergiant stars, have a corona.[4]