The dark dust feature splitting the Milky Way band from Cygnus toward Centaurus is the Great Rift.
The Great Rift is a broad lane of interstellar dust clouds that blocks visible light from millions of background stars. Seen from Earth, it appears to divide the bright Milky Way vertically, creating the impression that the galaxy has a dark crack running through its luminous band. The dust lies largely between the Solar System and the Sagittarius Arm, closer to the galaxy’s inner regions.
Its apparent path begins near Cygnus, where part of it is called the Cygnus Rift, continues through the Serpens–Aquila region and Ophiuchus, and reaches toward Sagittarius and Centaurus. The dark lane is therefore not an empty gap in the galaxy; it is a foreground obscuring structure.
This explains another common misconception: the Great Rift is not the Radcliffe Wave, a mapped arrangement of star-forming regions, and it is not the Local Bubble surrounding the Sun. Astronomers now understand the feature as a collection of cold, dusty molecular clouds, some of which are sites of star formation.