Originally Posted By: Leo Vuyk
galaxies whih are not inside our own material universe, are supposed to fail to create some shadow on the 2.7 Kelvin CMB radiation..
Such galaxies could be composed of antimatter (which shouldn't be shielded by dark matter, but attracted by it, instead) or maybe "parallel mater", which differs from matter inside of our galaxy. "Parallel matter" would annihilate in contact with matter our galaxy, but not completely. We can expect many similar surprises during future research.