406 Part V Galaxies and Beyond astronomical instruments reveal the Milky Way Galaxy to be a dy-namic system of stars and gas that continually gives birth to new stars and planetary systems. • Stellar winds and explosions make interstellar space a violent place. Hot gas tears through the atomic hydrogen that Flls much of the galac-tic disk, leaving expanding bubbles and fast-moving clouds in its wake. All this violence might seem dangerous, but it performs the great ser-vice of mixing new heavy elements into the gas of the Milky Way. • Although the elements from which we are made were forged in stars, we could not exist if stars were not organized into galaxies. The Milky Way Galaxy acts as a giant recycling plant, converting gas expelled from each generation of stars into the next generation and allowing some of the heavy elements to solidify into planets like our own. summary of key concepts 14.1 The Milky Way Revealed • What does our galaxy look like? The Milky Way Galaxy consists of a
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