Commonly known as the Lagoon Nebula, M8 was discovered in 1654 by the Italian astronomer Giovanni Battista Hodierna, who, like Charles Messier, sought to catalog nebulous objects in the night sky so they would not be mistaken for comets. This star-forming cloud of interstellar gas is located in the constellation Sagittarius and its apparent magnitude of 6 makes it faintly visible to the naked eye in dark skies. Located 5,200 light-years from Earth, M8 is home to its own star cluster: NGC 6530 (not visible in the image above). The massive stars embedded within the nebula give off enormous amounts of ultraviolet radiation, ionizing the gas and causing it to shine. (NASA)