What is the name of the luminous visible surface layer of the Sun?

The correct choice refers to the photosphere, which is the luminous visible surface layer of the Sun that emits light and is what we commonly see when we look at the Sun. The photosphere has an average temperature of about 5,500 degrees Celsius (around 9,932 degrees Fahrenheit) and is where sunspots, which are cooler regions, can also be observed.

In contrast, the heliosphere refers to the region of space influenced by the solar wind, while the atmosphere usually refers to the gaseous envelope surrounding a planet. The term "metrosphere" does not correspond to any recognized layer of the Sun or celestial body, making the photosphere distinctly the most accurate term for the Sun's visible surface layer.