Looking at invisible wavelengths that represent hydrogen emissions, he found that the sun's chromosphere, or lower atmosphere, extends 6,000 km (3,700 miles) beyond what is .
NASA launching new satellite to study sun - Tucson News Now NASA will launch the newest satellite to study the sun today. The Interface Region Imaging Spectrograh (IRIS) mission will study the area between the photosphere and the corona, which is known as the chromosphere.
June 26, 2013 - Tucson News Now