PHOTOSPHERE
The photosphere is the visible layer of the Sun. When we talk about the temperature of a star, we generally refer to the photosphere’s temperature, and the light of the mentioned layer is also useful to do chemical analysis of the stars. In the case of the Sun, the photosphere’s temperature goes from 4,200 °C to 5,700 °C.
On this layer, we can see different phenomena such as sunspots, which are regions of reduced temperatures caused by local magnetic fields that inhibit the escape of hot material from the innermost layers. These spots appear and then disappear as it is related to a solar cycle of eleven years in which the Sun changes its global magnetic field, which means that the north pole turns into the south pole, and vice-versa. Like so, if in one year we see many sunspots, after five or six years we will see just a few. A small telescope with a suitable solar filter can help to observe these sunspots.
Solar telescopes are specially designed to observe the solar surface with higher contrast. We can obtain high-resolution images of solar flares, sunspots, spicules, and granulation with a particular filter called H-alpha filter (Hα).
Sun images during periods of higher and lower activity in the photosphere.
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