This infrared image from NASA's Spitzer Space Telescope shows what may be the most luminous group of superstars in the entire Galaxy. Such groups—named OB associations for the O and B spectral types of their hot, blue suns—sculpt vast regions of space through their radiation and supernova explosions. The newly discovered Dragonfish association (pictured) is 32,000 light-years distant and hides behind thick dust in the constellation Crux, the Southern Cross: If 2.5 million photons of yellow light set out toward us, only one photon would make it to Earth. Fortunately, infrared photons penetrate the dust more easily. As astronomers in Canada will report  in an upcoming issue of The Astrophysical Journal Letters, the Dragonfish harbors about 400 hot, blue, luminous stars. The stars' extreme ultraviolet radiation strips electrons from protons, thereby ionizing interstellar hydrogen gas and setting it aglow. But the real action will begin when the stars start exploding—probably within a few million years—triggering the birth of new stars and further enriching the Milky Way with oxygen, magnesium, and other elements that terrestrial planets and their inhabitants need.
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