9781422279465

2

Helium

Spotting It in the Sun In 1868, two astronomers were working independently on study- ing the spectral lines emitted by the Sun. Every element has a unique spectral line. In this way, they are similar to fingerprints. Each element displays its spectral line when the wavelengths of the elements are observed through a special filter or a spectrometer; this is much like visible light breaking into separate lines when passed through a prism.

The French astronomer Pierre Janssen was working in India and looking at the spectrum of the light and energy emitted by the Sun during a solar eclipse. He observed a yellow spectral line with a wavelength of 587.49 nanometers —a wavelength that had not been seen before, in space or on Earth. He suspected he had found a new element in the solar radiation.

These colors represent the wavelengths of light passing through helium.

12