The distribution of galaxies in the universe is not regular, but clumpy. Galaxies, some of them one billion light years from the sun, tend to clump together into huge supercluster formations. This is an image of the Perseus-Pisces supercluster. Some galaxies are visible with the naked eye, but astronomers discovered these distant galaxies with the help of A) space probes. B) satellite imaging. C) manned space craft. D) X-ray and infrared telescopes.