The Sun's atmosphere consists of several distinct layers, each with unique characteristics:
Layers of the Sun's Atmosphere
- Photosphere : This is the lowest and deepest layer of the Sun's atmosphere and the one we can directly observe. It extends about 250-300 miles (400 km) above the Sun's surface. The photosphere is where most of the Sun's visible light is emitted, with temperatures ranging from about 6500 K (bottom) to 4000 K (top). It appears as the bright "surface" of the Sun and shows features such as sunspots and granulation. This layer is visible because it is the region where the Sun becomes opaque to visible light, allowing photons to escape into space
- Chromosphere : Above the photosphere lies the chromosphere, extending roughly 250 to 1300 miles (400 to 2100 km) above the surface. Temperatures here rise from about 4000 K at the bottom to around 8000 K at the top. The chromosphere is hotter than the photosphere and can be seen as a reddish glow during total solar eclipses but is not visible under normal conditions due to the brightness of the photosphere
- Transition Region : This is a very thin, narrow layer (about 60 miles or 100 km thick) between the chromosphere and the corona where the temperature rises abruptly from about 8000 K to around 500,000 K. It acts as a boundary between the cooler chromosphere and the extremely hot corona
- Corona : The outermost layer of the Sun's atmosphere, starting about 1300 miles (2100 km) above the photosphere, extends millions of kilometers into space. The corona's temperature is extremely high, reaching millions of kelvin (up to a few million K). It is visible only during total solar eclipses or with special instruments called coronagraphs. The corona appears as a white halo or streamers around the Sun during eclipses and is the source of the solar wind
Which Layers Can We See and Why?
- Visible to the Naked Eye : Only the photosphere is visible under normal conditions because it is the layer from which most visible sunlight escapes. It acts as the Sun's "surface" in visible light.
- Visible During Total Solar Eclipses : The chromosphere and corona become visible during total solar eclipses. The photosphere is blocked by the Moon, allowing the fainter chromosphere's reddish glow and the corona's white halo to be seen.
- Not Visible Normally : The transition region is too thin and faint to be seen directly.
The reason the photosphere is visible is that it is the layer where the Sun becomes opaque to visible light, allowing photons to escape into space. The chromosphere and corona are much fainter and hotter layers above the photosphere, visible only when the bright photosphere is obscured, such as during an eclipse
. In summary, the Sun's atmosphere includes the photosphere, chromosphere, transition region, and corona. We see the photosphere directly as the Sun's surface, while the chromosphere and corona are visible only during total solar eclipses due to their faintness compared to the bright photosphere. The transition region remains invisible to the naked eye due to its thinness and faint emission.
