Hello Lori Here is the definition I grabbed from the SOHO page http://sohowww.nascom.nas...xplore/glossary.html An atmosphere is generally the outer most gaseous layers of a planet, natural satellite, or star. Only bodies with a strong gravitational pull can retain an atmosphere. Atmosphere is used to describe the outer layer of the Sun because it is relatively transparent at visible wavelengths. Parts of the solar atmosphere include the photosphere, chromosphere, and the corona. Dawn