A Large Unrecorded Nebula

The note by Mr. Melotte with reference to four fairly conspicuous nebulae shown on Franklin-Adams chart plates (M.N., 86, 636, 1926) suggests that it may be of interest to call attention to a large irregularly circular nebulosity in Centaurus and Musca, which does not seem to have been recorded heretofore. The position of the nebula, which immediately follows the southern part of the "Coal Sack", the dark nebulosity at the base of the Southern Cross, is 13^h 18^m, −63°.5, and its diameter on the average is 2°.5. The nebula is generously crisscrossed with wisps of dark nebulosity; in fact, throughout this whole region of the Milky Way from α Centauri to η Carinae the best small-scale photographs show extensive traceries of dark nebulosity. One of the most conspicuous of these obscurations extends from the southern preceding corner of the Coal Sack in a southwesterly direction for ten degrees.

There is no very bright star in or near the bright nebula described above, though θ Musca, of Class Oap and magnitude 5.4, is at 13^h 2^m, −64°.8. Among the stars within the boundaries of the nebula the following are the brightest:

The nebula, as well as much of the surrounding obscuring nebulosity, is shown on the plate facing page 12 of "The Universe of Stars," published in 1926 by the Harvard Observatory.

Harlow Shapley