From the July 2005 issue

Phil Harrington’s binocular universe (September 2005)

Go on the prowl for dark nebulae.
By | Published: July 25, 2005
Unlike most of the constellations, many of which we can trace their origins to the dawn of civilization, Scutum the Shield was created relatively recently by famous Polish astronomer Johan Hevelius. Three years after his death in 1687, Hevelius’ Prodromus Astronomiae was published. Inside, he had created several new constellations, including Canes Venatici, Lacerta, Leo Minor, Lynx, Sextans, Scutum, and Vulpecula.

Scutum is drawn among the faint stars found just south of Aquila and represents the shield of John Sobieski, a pivotal figure in 17th-century Poland. The country’s nobility crowned Sobieski King John III after he successfully resisted the Turkish advance during the Battle of Vienna in September 1683.

Hevelius’s Firmamentum, which appeared in 1690, was the first star atlas to rival Bayer’s Uranometria in scope, accuracy, and usefulness. It differs from the other atlases pictured here because Hevelius chose to picture the constellations as they would be seen from the outside of a celestial globe. This image shows Scutum the Shield, one of seven constellations still in use invented by Hevelius. Scutum is a tiny constellation that is completely visible for anyone living south of latitude +74°.
Linda Hall Library
If you get to a truly dark location, you’ll immediately see that the Scutum Star Cloud glows against the fainter, surrounding Milky Way. Aim your binoculars its way, and you’ll also see more there than M11 and M26. Take a careful look to spot some dark rifts wafting across the bright background. These dark nebulae and patches of opaque interstellar dust grains block the light behind them. It takes dark, transparent skies to see dark nebulae. Scan the region slowly — and be patient to see these objects.

American astronomer Edward Emerson Barnard was the first to research dark nebulae. His catalog, Photographic Atlas of Selected Regions of the Milky Way, contains about 350 entries. Yerkes Observatory — where Barnard made many of his discoveries — published the catalog posthumously in 1923.

Today, we often refer to dark nebulae by their “B,” or “Barnard” catalog number in much the same way as we talk about the Orion Nebula as M42. The most obvious dark nebulae in Scutum are B111 and B119a. You can spot both to the north-northeast of M11. They appear as large, kidney-shape patches that almost touch each other at their southern tips. B111 forms the northeastern edge of the Scutum Star Cloud and appears many times larger than B119a in photographs. Look for a “peninsula” of about half a dozen 8th- to 10th-magnitude stars wedged between the nebulae, as well as an L-shape asterism of stars just north of B119a. The center star of that asterism looks orangish through binoculars.

B318, a long, very thin dark cloud stretches east-west. Look for it just to the south of M11. Farther south you can find B112, a small, egg-shape dark nebula measuring about 20′ across. For scale, the Full Moon measures 30′ across.