Here's why:
* Early Observations: Early astronomers could only observe the photosphere, the visible surface of the sun. They didn't have the tools to study the chromosphere, which is a thin layer above the photosphere.
* Spectroscopy: The development of spectroscopy allowed scientists to analyze the light coming from the sun. By studying the spectral lines, they discovered the presence of hydrogen in the chromosphere.
* Solar Eclipses: During total solar eclipses, the moon blocks out the photosphere, allowing scientists to observe the chromosphere. This provided further evidence of hydrogen's presence.
While other elements are present in the chromosphere, hydrogen is the most abundant and was the first to be identified.
