Astronomy Picture of the Day . ... 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. ... Welcome to the December Solstice, first day of winter in the north and summer in the southern hemisphere of planet Earth. ... Finding Dark Matter . ...