From NASA:
"So why does it look like a big X? A likely explanation is that the central star - actually a close pair of stars - is surrounded by a thick dust torus which pinches the otherwise spherical outflow into tip-touching cone shapes. Because we view the torus edge-on, the boundary edges of the cone shapes seem to form an X. The distinct rungs suggest the outflow occurs in fits and starts. About 2,300 light-years away toward the fanciful constellation Monoceros, the Red Rectangle nebula should be transformed into a glorious planetary nebula as its cool central star becomes a hot white dwarf over the next few thousand years."
NASA again:
"What could cause a nebula to appear square? No one is quite sure. The hot star system known as MWC 922, however, appears to be imbedded in a nebula with just such a shape."
Some strange information in the Red Sqaure Wikipedia article suggests that the nebula is lucky, and that a competing team named after the Red Square will earn its blessing. Knock on wood.
