shock waves from supernovae, exploded stars that emit vast amounts of energy.
Last year, using telescopes aboard an orbiting satellite, scientists discovered one such field- the largest known object in the galaxy -measuring 1,000 light years across in the constellation Cygnus. This "superbubble," located near the center of the Milky Way (Earth is on the outer edge), and others like it, may be prime engines of star forma- tion, report Cash and Charles, astronomers at the University of...