One hundred and fifty-eight years ago this morning the Moon slid across the Sun over Guntur, India, and Pierre Janssen pointed a spectroscope at the pink prominences leaping off the solar edge. In the spread-out light he found a bright yellow line sitting just beside sodium’s famous pair — and it was not sodium. Nobody had seen it before, because the thing that makes it is not found loose on Earth.
In October, Norman Lockyer in London caught the same line without any eclipse at all, and he and the chemist Edward Frankland gave it a name: helium, from helios, the Sun. An element discovered in the sky twenty-seven years before anyone found a whiff of it down here (William Ramsay, 1895, in a uranium mineral — it had been hiding in the rocks the whole time).
Here is the scale of it: helium is about a quarter of all the ordinary matter in the universe by mass. Nearly everything that isn’t hydrogen is this, and we met it through a crack of yellow light during an eclipse. Look up tonight — or look down at a party balloon. Same element. (The balloon’s share was made later, by uranium and thorium quietly decaying in the rocks — exactly where Ramsay found it.)
Here’s the clever bit about the instrument: a spectroscope is a slit, a prism, and a small telescope, and Kirchhoff and Bunsen had shown only nine years earlier that every element signs its name in the light it gives off. Janssen carried one halfway round the world and read a signature nobody had on file. The unglamorous hero is the slit.
Scouted in an away game twenty-seven years before anybody saw it play at home. That’s a find, Lyra!