This Day, That Year – August 18

This day in history we feature Helium. French astronomer Pierre Janssen discovers helium on this day in 1868.

Trivia – Helium

Helium was discovered in the gaseous atmosphere surrounding the Sun by a bright yellow line in the spectrum of the solar chromosphere; this line was initially assumed to represent the element sodium. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India.

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That same year the English astronomer Joseph Norman Lockyer observed a yellow line in the solar spectrum that did not correspond to the known D1 and D2 lines of sodium, and so he named it the D3 line. Lockyer concluded that the D3 line was caused by an element in the Sun that was unknown on Earth; he and the chemist Edward Frankland used the Greek word for sun, hēlios, in naming the element. The British chemist Sir William Ramsay discovered the existence of helium on Earth in 1895. Ramsay obtained a sample of the uranium-bearing mineral cleveite, and, upon investigating the gas produced by heating the sample, he found that a unique bright yellow line in its spectrum matched that of the D3 line observed in the spectrum of the Sun; the new element of helium was thus conclusively identified. In 1903 Ramsay and Frederick Soddy further determined that helium is a product of the spontaneous disintegration of radioactive substances.

Source – Britannica

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