[madbadgalaxyman (Robert)]

The shell structure photographed by Greg appears to be just one section of an even much larger shell which extends a long way to the North.

However, the northern parts of the shell are not nearly as well behaved.....Very chaotic and complex in appearance.

A literature search for scientific papers since 1975 reveals that next to nothing is known about the origin and evolution and future of this vast H-alpha emitting shell, despite its extreme prominence in the southern Milky Way and despite the fact that the candidate energizing objects (NGC 6231, Scorpius OB1 association, plus the consequent core-collapse supernovae) seem to be obviously visible.

Here is the entire shell (in centre of image) from the SuperCOSMOS H-alpha survey.