Helium was discovered on the Sun 27 years before anyone found it on Earth — spotted as an unexplained yellow line in sunlight during an 1868 eclipse and named after Helios, the Greek sun god, long before the gas was identified in any mineral on this planet.

On 18 August 1868, the French astronomer Pierre Janssen observed a total solar eclipse from Guntur, in India. Pointing a spectroscope at the Sun’s chromosphere, the thin layer just above its visible surface, he recorded a bright yellow line at a wavelength of about 587.5 nanometres. A spectral line is a fingerprint. Each chemical element, [...] The post Helium was discovered on the Sun 27 years before anyone found it on Earth — spotted as an unexplained yellow line in sunlight during an 1868 ecl