Mary Crone Odekon
Kenan Chair of Liberal Arts and Professor of Physics
The universe is much, much messier than it would appear from a map of the stars.
In Demetrius Oliver’s Messier (2013), one hint of this messiness comes from the small, hollow circles, different from the filled-in dots representing simple stars. The hollow circles do not have normal star names like Deneb or Vega, but instead, catalog numbers like M 52 and M 39. Most of these objects are invisible in the sky unless viewed through binoculars or a telescope, when they appear as fuzzy smudges of light, still not betraying the fact that they represent a range of complicated compound systems of gas, stars, and dust—some at such great distances that billions of stars appear as one.
In fact, these are not only messier objects, but also Messier objects, listed in the eighteenth-century catalog of French astronomer Charles Messier. He was a comet hunter who mapped out the positions of fuzzy objects in the night sky. The fuzzy objects that moved slowly through the constellations and then disappeared were comets, balls of rock and ice swinging past the sun in their orbits. The fuzzy objects that stayed in place became known as Messier objects. We now know that Messier objects are much larger than comets, and so distant that we cannot discern their motion across the sky. Messier objects include different kinds of systems: vast nebulae of gas and dust, clusters of stars, and entire galaxies.
What Charles Messier might have guessed, but could not have known for sure, was the extent to which star maps are figments of our point of view. The night sky is intensely three-dimensional, with some objects trillions of times farther away than others. In Oliver’s Messier, both the photograph itself and its primary subject, the map, are essentially two-dimensional structures. But we see the map from outside its two-dimensional world, at an angle, with only the center in focus—and, as if to drive the point home, a paper clip bent into a three-dimensional shape that echoes the two-dimensional illustration of a constellation below it.
The constellation below the paper clip, Cepheus (the name referring to the king of Ethiopia in classical Greek mythology), has a special role beyond its central position in the photograph. The prototype variable star that led to our discovery of the galaxies and the great depths of space is a star in this constellation—the one just outside the paper clip, separated from the other bright stars in Cepheus.
To push a little harder, there are reasons to describe the universe in more than three dimensions. Einstein’s relativity, which we can use to understand the bending of light and the orbit of Mercury, uses a four-dimensional space-time. Even more dramatically, one attempt to combine the effects of gravity and quantum physics (as we need to in the context of black holes and the early history of the universe) describes strings that vibrate in a ten-dimensional space-time.
Why take a photograph of a map? I like the way it draws attention to how we extract, impose, or just see a simplified, less messy version of reality. Maps, physical or not, can be appealing and safe. How we make them into useful tools for extracting specific truths depends partly on having constant reminders in the background—or foreground—that they are just one slice through the universe.