An extensive atmosphere consisting of two main layers stretches beyond the photosphere. The chromosphere, just above the photosphere, extends out about 3,100 miles (5,000 km), its temperature increasing with height to about 36,000°F (20,000°C). The outer layer, the corona, which extends into space for millions of miles, is hotter still, at 3.6 million °F (2 million °C). Such high temperatures are unexpected, and at present there is no accepted explanation for them.
The atmosphere is not usually visible but lost in the dazzling light of the Sun. The pinkish chromosphere and the pearly white corona can be seen when the disk is obscured by, for example, the Moon during a total eclipse. Still invisible from view is the solar wind, tiny particles streaming away from the Sun.
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