Give the history of coronium and tell how it increased our understanding of the sun

During the temporary moments of the eclipse, if the Moon's angular size is giant enough that each the surface and also the layer are blocked. With the photospheric light-weight removed, the pattern of spectral lines changes dramatically. The intensities of the standard lines alter, suggesting changes in composition or temperature, or both, the spectrum shifts from absorption to emission, and a wholly new set of spectral lines suddenly are seen.
These new lines were initially ascertained throughout eclipses in 1920.
For years after, some researchers attributed them to a brand new nonterrestrial component, that they named as "coronium."

When photosphere and the chromosphere are unrecognized by the Moon during a solar eclipse, the faint corona becomes visible.