Superbubble

[2] 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 exterior stars at distances greater than a few hundred light years.

The strongest stellar winds release kinetic energy of 1051 ergs (1044 J) over the lifetime of a star, which is equivalent to a supernova explosion.

When stars die, supernova explosions, similarly, drive blast waves that can reach even larger sizes, with expansion velocities up to several hundred km s−1.

Stars in OB associations are not gravitationally bound, but they drift apart at small speeds (of around 20 km s−1), and they exhaust their fuel rapidly (after a few millions of years).

These shells were first observed in line emission at twenty-one centimeters from hydrogen,[6] leading to the formulation of the theory of superbubble formation.