... Hot Stars in the Southern Milky Way . ... Hot blue stars, red glowing hydrogen gas, and dark, obscuring dust clouds are strewn through this dramatic region of the Milky Way in the southern constellation of Ara (the Altar). About 4,000 light-years from Earth, the stars at the left are young, massive, and energetic. ... A Solar System Portrait . ... On planet Earth, observer Barry Reynolds photographed the expanding shock front (left) in the light emitted by hydrogen atoms at the solar surface. ...