... Abell 1795: A Galaxy Cluster s Cooling Flow . ... Astronomers have realized since the early 1970s that the larger swarms, immense clusters of galaxies millions of light-years across, are immersed within tenuous clouds of hot gas which glow strongly in x-rays. ... The Earth's surface is broken. ... Earth's North Magnetic Pole . ... A magnetic compass does not point toward the true North Pole of the Earth. Rather, it more closely points toward the North Magnetic Pole of the Earth. ...