1895

Milky Way Dark Lanes

Edward Emerson Barnard (1857–1923), Max Wolf (1863–1932)

People fortunate enough to live in or at least occasionally visit truly dark, non-light-polluted night skies on moonless nights are treated to a stunning view: the grand Milky Way sweeps from horizon to horizon, with bright starry bands and black inky lanes stretching out like a celestial Jackson Pollock painting splashed across a grand cosmic canvas. On such wonderful nights it’s easy to understand our ancestors’ reverence for the night sky, as well as their need to try to make sense of what they were seeing.

In the late nineteenth century, many of the world’s major cities could still be considered “dark sky” observing sites; the electrification of the night sky didn’t become truly ubiquitous until sometime after World War II. Thus, the American astronomer E. E. Barnard jumped at the opportunity to move to the University of Chicago in 1895 to gain access to what had just become the world’s largest refracting telescope, the giant 40-inch (102-centimeter) lens at Yerkes Observatory. Armed with a great telescope and his newfound interest in the nascent field of astrophotography, Barnard began taking the best data ever acquired of bright star fields and dark, seemingly empty gaps across the Milky Way’s grand sweep.

An important collaborator on Barnard’s Milky Way studies was the German astronomer and astrophotographer Max Wolf. Wolf was aware that many astronomers were puzzled by the Milky Way’s dark lanes—what the English astronomer William Herschel had called holes in the sky. Barnard’s photos and Wolf’s analysis revealed that these “holes” weren’t really holes at all—careful observations could reveal faint embedded stars, or even background stars, that could be used to derive the properties of the dark lanes.

Wolf made a convincing and ultimately accurate argument that the dark areas in the Milky Way are enormous clouds of relatively opaque dust that obscure the otherwise blazing light of the background stars and prevent them from shining through. He noticed that the dark lanes were often associated with pockets of bright nebulosity, potentially from newly formed stars, and deduced that the dark regions might be cosmic cocoons, places where dust and gas are being compressed and thickened and are “about to form new suns.” Wolf and Barnard’s early speculations about the origin of the dark lanes have turned out to be spot-on.

The glorious spectacle of the Milky Way and its dark, dusty lanes rises over Long’s Peak (14,259 feet [4,346 meters] high), in the Rocky Mountain National Park in Colorado.