22.3: Outer Layers of the Sun

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What can you see during a solar eclipse?

A solar eclipse is kind of like a field trip to the Sun from Earth. You can see something (with special tinted glasses) that you don't usually see. The Sun has a remarkable ring of light around it. This is the corona. If you have a chance to see a solar eclipse, you should do it.

The Outer Layers

The three outer layers of the Sun are its atmosphere. The layers are, from inside to outside, the photosphere, the chromosphere, and the corona.

The Photosphere

The photosphere is the visible surface of the Sun (Figure below). It's the part that we see shining. Surprisingly, the photosphere is also one of the coolest layers of the Sun. It is only about 6,000°C.

Layers of the Sun

The Sun's atmosphere contains the photosphere, the chromosphere, and the corona. This image was taken by NASA's Spacelab 2 instruments.

The Chromosphere

The chromosphere (Figure below) lies above the photosphere. It is about 2,000 km thick. The thin chromosphere is heated by energy from the photosphere. Temperatures range from about 4,000°C to about 10,000°C. The chromosphere is not as hot as other parts of the Sun, and it glows red. Jets of gas sometimes fly up through the chromosphere. With speeds up to 72,000 km per hour, the jets can fly as high as 10,000 km.

The chromosphere of the Sun

The chromosphere.

The Corona

The corona (Figure below) is the outermost part of the Sun's atmosphere. It is the Sun’s halo, or “crown.” With a temperature of 1 to 3 million K, the corona is much hotter than the photosphere. The corona extends millions of kilometers into space. Sometime you should try to see a total solar eclipse. If you do, you will see the Sun’s corona shining out into space.

The Sun's corona during a total solar eclipse

During a total solar eclipse, the Sun's corona becomes visible, peeking out from behind the Moon.

Summary

The photosphere is the part of the Sun that we see shining.
The chromosphere is an active layer that glows red.
The corona is the halo around the Sun.

Review

What layer of the Sun do you see during a total solar eclipse?
What are the distinctive characteristics of the photosphere?
What are the distinctive characteristics of the chromosphere?
What is the corona?