A small dwarf irregular galaxy spanning 5 thousand light years across, Sextans A is located only 5 million light-years away. 100 million years ago, something mysterious started a new wave of star formation in Sextans A's center . Massive short-lived stars exploded in supernovae that caused more star formation and yet more supernovae, ultimately resulting in an expanding shell . Today, young blue stars highlight areas and shell edges high in current star formation, a shell that from our perspective appears roughly square . In the above picture , a bright orange star in our own Milky Way Galaxy appears superposed in the foreground.
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