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Spectroscopy

December 14, 2009 Leave a comment

A multitude of information can be and is gathered from the world, but oft overlooked is the one thing that gives this planet life. That is light, and more specifically light from the Sun. To many, when the Sun is viewed, this signals that it is time for the day to begin and for our work, school, or daily routine to commence. But what is the Sun made of? For that matter, what are stars made of in general?

This question began to be seriously considered and studied during the 19th century. Several scientists in the early 19th century began to contribute to early spectroscopy, which, historically, is the use of visible light dispersed according to its wavelength by a prism. This study led to the discovery by Charles Wheatstone that different metals could be easily distinguished by the different bright lines in the emission spectra of their sparks. This discovery launched the study of spectral analysis.

Diffusion of light

In 1854, a scientist named David Alter published an article that included the spectral radiance, which is the measurement that describes the amount of light that passes through or is emitted from a particular area and falls within a given angle in a specific direction, of twelve different metals. He went on to apply this in a later article to six different gases as well. This article contains a paragraph where he envisioned the application of spectrum analysis to astronomy in regards to the combustion of shooting stars or meteors.

Each element has a spectral fingerprint that is specific to that element. This is detected by analyzing either the emission or the absorption spectrum. The emission spectrum is used when the element being analyzed produces light, such as the spark from a combusting metal or a star. The absorption spectrum is the light that is left over after passing through a solid or gas. The cataloging of elements found on Earth has enabled scientists to analyze the spectral fingerprint of visible stars in our galaxy. This in turn, allows scientists to understand what elements make up specific stars.

Spectral analysis of our sun has yielded the elemental make up of our life-giving star. The sun, for the most part is hydrogen. In fact, it is 70% hydrogen by mass. The other main element found within the Sun is helium, which was actually discovered through spectral analysis of the sun prior to be found on Earth. The Sun is 28% helium by mass. 1% of the sun is oxygen and the remaining 0.5% contains other elements including, carbon, nitrogen, silicon, magnesium, neon, iron, and sulfur. The Sun is about 4.5 billion years old and still has about 5 billion years worth of hydrogen left to burn.

Without spectral analysis, it would be impossible to classify the elemental make up the Sun and many other stars that have been identified. This science’s impact has allowed humanity to better understand the similarities between the Sun and many other stars within our vast universe down to elemental composition.

References

http://chemistry.about.com/od/geochemistry/a/sunelements.htm

http://imagine.gsfc.nasa.gov/docs/science/how_l1/spectral_what.html

http://curious.astro.cornell.edu/question.php?number=244

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