Red rectangle nebula

There had been some speculation that the highly symmetrical spread of light from nebulae like the Red Rectangle Nebula, and the Red Square Nebula, are the result of advanced Kardashev level II/III alien civilizations engaging in stellar scale mega-engineering. Of course, unless evidence emerges to support such postulations, the most likely explanations remains that the Red Rectangle Nebula is just an unusually shaped natural proto-planetary nebula.