What is a Fraunhofer Line? page all

KOMPAS.com – German physicist Joseph von Fraunhofer (1787–1826), invented an instrument called a spectroscope which contained a diffraction grating.

When Fraunhofer used this tool to analyze light from the Sun, he found dark lines on a continuous spectrum. These lines are known as Fraunhofer line.

Diagram showing Fraunhofer lines – dark lines on a continuous spectrum.

Reported from BBC, The sun and other stars produce all wavelengths of light.

As the light passes through the cooler outer atmosphere, the gas atoms absorb certain wavelengths of light, producing a spectrum of absorption lines that humans can see from Earth.

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Scientists in the 19th century were able to compare these dark lines to the emission line spectra of known elements and identify what elements were present in the cooler atmosphere.

Today, using much more sophisticated technology, astronomers have discovered tens of thousands of Fraunhofer lines.

What happens to light before it reaches Earth?

When looking at an image of the Sun, the visible surface is called the photosphere.

The photosphere is the region hundreds of kilometers thick, where the Sun changes from opaque to transparent.

The photosphere is not actually the outermost surface. The sun extends thousands of kilometers beyond the photosphere, but is usually not visible from Earth.

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Within this thin layer of the Sun (thin compared to the rest of the Sun), sunlight is created and some colors disappear.

The lower region of the photosphere has a temperature of about 5,500 degrees Celsius and glows white-hot.

Any object that glows due to high temperatures gives off a complete spectrum, i.e. has all the colors of the rainbow.

As this light travels upward, into the higher regions of the photosphere, its temperature drops by several thousand degrees.

Although most of the light passes through it, some of the light is absorbed by the cooler gas.

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Only certain colors are removed because the chemical elements in the photosphere can only absorb certain wavelengths of light and different wavelengths correspond to different colors.

For example, sodium absorbs some yellow light at a wavelength of about 5.89×10 -7 m.

These absorbed colors cause Fraunhofer lines. By measuring precisely the wavelengths of the missing color, namely Fraunhofer lines, and how much light is actually absorbed, astronomers have learned a lot about the temperature inside the Sun and its chemical composition.

In addition, scientists can also study other stars in the sky by looking at the absorption lines in their spectrum.

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