In August 1868, the Sun briefly became a laboratory for astronomers gathered in India to watch a total solar eclipse. Among them was the French astronomer Pierre Jules Janssen, who turned a spectroscope towards the bright prominences rising around the eclipsed solar disc.

In August 1868, the Sun briefly became a laboratory for astronomers gathered in India to watch a total solar eclipse. Among them was the French astronomer Pierre Jules Janssen,…

Astronomers observed a unique spectral line during an 1868 solar eclipse in India. This unexplained yellow line suggested an element unknown on Earth at that time. Norman Lockyer…