The Discovery of Helium
Part of the Inorganic Chemistry For Dummies Cheat Sheet
Upon its discovery by French astronomer Pierre J. C. Janssen in 1868, helium was thought to exist on the sun, but not here on the earth. As he was observing a solar eclipse in India, Janssen noticed a bright yellow spectral line.
The sun shines every day. Regardless of how far north or south you live on this planet, the sun can still reach you. The sun is a great big ball of fire several million miles away. In fact, it’s a huge nuclear reactor, filled with explosions that cause energy to be blasted away and emitted in all directions.
The light that you see from the sun comes from all the photons being sent out into space from the sun, and the color of the light can be used to determine what elements are present thanks to our understanding of electron energy levels and atomic spectroscopy. In short the theory goes like this . . . electrons orbit around an atom that holds as many electrons as is allowed for that atom.
Each electron has a certain discreet energy level, and when the electron is excited you can see the energy levels using a prism, for example. A prism splits up white light; it slows it down due to diffraction, and you can get the full spectrum of the rainbow from white light. But some sources of white light are missing some bands of the rainbow colors; this depends on the source of the light. The bands that are missing act like fingerprints for chemical elements, and these “fingerprints” are unique, so you can use them to identify elements, even if they are very far away like the stars and other planets. It was by looking at the sun with such a setup that helium was first discovered.
The light from the sun had bands in it that were composed of an unknown material, like nothing that had been analyzed on earth yet. It was named after the sun, Helios. The discoverer Pierre J. C. Janssen had to travel to India to make his observation during a solar eclipse in 1868. But it was later discovered that helium is present on the Earth, and later yet was discovered among uranium minerals. It just goes to show that you don’t have to go all the way to the sun to find your answer — it’s probably right here among us already. You just have to learn to look in the right way.