Mapping the universe

Abstract

The varieties of astronomical mapping are presented, starting with maps of the celestial sphere. Important map projections are considered, including gnomonic projections which are particularly good for star charts. When telescopes arrived, astronomers began to make maps of other worlds, including influential maps of Mars by Schiaparelli and maps of the Moon made during the Apollo era. I discuss map projections specifically designed for Mars and the Moon. Map distortions are examined: area, local shape, flexion, lopsidedness, distances, and boundary cuts. Spacetime maps include Martin Kruskal's map of the interior of the black hole. Our map of the Sloan Great Wall of Galaxies, 1.37 billion light-years long, and the famous WMAP satellite map of the cosmic microwave background are described. Finally, my "Map of the Universe" displays everything in the universe on a logarithmic map: from the Earth to manmade satellites; to the Moon, Sun, and planets; to nearby stars; to our Milky Way, and other galaxies in the Local Group and Virgo supercluster; to the distant galaxies in the Sloan Digital Sky Survey; and finally, to the Cosmic Microwave Background, the most distant thing we can see.