A superbubble is a cavity hundreds of light years across, filled with 106 K gas blown into the interstellar medium by multiple supernovae and stellar winds. The solar system lies near the center of an old superbubble, known as the Local Bubble, whose boundaries can be traced by a sudden rise in dust extinction of stars at distances greater than a few hundred light years.
Read more about Superbubble: Formation, Superbubble Examples