The surface of the sun, or photosphere, is a yellow-colored layer of thick, hot gases marked with dark spots, known as sunspots. It is the lowest visible layer of the sun.
The photosphere is 5,780 degrees Kelvin (K), which is relatively cool compared to the inside, measured in the millions of degrees, and the atmospheric edge, which is also measured in the millions of degrees.
The gases that make up the photosphere are completely opaque, meaning that you cannot see through them. Therefore, stating that the sun has “surface” is a misnomer, for the photosphere is not solid.
The photosphere is above the solar convection zone, where heat from the core radiates outward and below the chromosphere, where heat is transferred to the outer layer of the sun, called the corona.
The photosphere is constructed of convection cells called granules, which are cells of hot gas 1,000 km in diameter. Each granule lives 8 to 9 minutes, which produces a “boiling” effect.
Sunspots are cooler regions of the photosphere that appear dark because of their lower temperatures of 3,800 degrees K versus 5,780 degrees K. Sunspots can vary in size up to 50,000 km in diameter.
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