The element first discovered in the Sun’s spectrum before being found on Earth was helium.
The first evidence appeared during the total solar eclipse of August 18, 1868, when astronomers observed a bright yellow spectral line in the Sun’s chromosphere. English astronomer Norman Lockyer later studied the same feature and argued that it came from an element unknown on Earth. He named the proposed element helium, from Helios, the Greek word for Sun.
Helium’s spectral signature was distinctive because atoms emit or absorb light at particular wavelengths. The yellow line, later identified as the D3 line near sodium’s D lines, initially seemed mysterious. In 1881, Luigi Palmieri reported helium’s spectral line in material associated with Mount Vesuvius, but the discovery was not firmly established until 1895.
That year, William Ramsay isolated helium from the uranium mineral cleveite, while Per Teodor Cleve and Abraham Langlet independently obtained it in Sweden. Helium therefore became a striking example of astronomy leading chemistry: scientists identified an element in a star before isolating it in terrestrial material.