Answer: Helium

The first scientific observation of the first noble gas, Helium, was in 1868 when it was detected as a bright yellow line during a spectroscopic observation of the Sun (during a total solar eclipse) conducted by French astronomer Jules Janssen. Although Janssen noted it, the line was believed to be representative of the element sodium.

It wasn’t until later in the same year that English astronomer Norman Lockyer observed the same spectrum line—he also made note of it and named it the D3 Fraunhofer line (Fraunhofer was a German physicist after which the dark bands separating the spectral colors were named). He named it such because it was near the known lines D1 and D2, found in sodium. He concluded that it was actually a previously unobserved element that was unknown on Earth and only found in stars like the Sun.

In a nod to Greek mythology, Lockyer and the English chemist Edward Frankland named the element Helium, derived from the name of the Greek god of the Sun—Helios.