Spectacular spectrum reveals Sun's chemistry

This is what visible light from the sun looks like if you split it into its constituent colours. But playing with a prism at home will not give you this high-resolution masterpiece, which was created using a sophisticated spectrometer fixed to the world's largest solar telescope at the Kitt Peak National Observatory in Tucson, Arizona. The spectrometer splits light from the sun into two beams and sends them towards two mirrors, which bounce the light back to a detector where the beams recombine. Via a complex mathematical technique, the resulting interference pattern appears as a spectacular solar spectrum, covering the entire range of visible light.

What are the dark blobs in the image? These are known as Fraunhofer lines after German physicist Joseph von Fraunhofer, who first studied them in detail in 1814. They are caused by specific elements in the outer layers of the sun absorbing a characteristic wavelength of light - the missing wavelength showing up as a dark line. This barcode-like image tells us about the elements present in the sun. For instance, the broad dark patch in the red part of the spectrum (upper right) indicates the presence of hydrogen and the two prominent lines in the yellow part are sodium.

As well as helping us to study the chemical composition of stars, such spectra can also tell us about the atmosphere of planets orbiting other stars.

via Spectacular spectrum reveals Sun's chemistry - space - 04 March 2009 - New Scientist.