What is the photosphere?

The photosphere is defined as the visible surface of the sun, which emits the light and heat that we perceive. It is the layer from which sunlight originates and has a temperature of about 5,500 degrees Celsius (approximately 9,932 degrees Fahrenheit). This layer is critical in solar studies because it is what we can observe directly from Earth with the naked eye under proper conditions, such as during a solar observation.

While the photosphere is often discussed in relation to various solar phenomena, such as sunspots and granulation, its primary characteristic is being the boundary where we can see sunlight. This distinguishes it from other layers of the sun, such as the outer atmosphere, which is not directly visible without special instruments, or the core, which is not part of the visible surface at all. Therefore, defining the photosphere as the visible surface of the sun accurately captures its significance and role in solar physics.