April to August (the southern parts of the Rift are usually visible in southern latitudes)
A narrow band of dark obscuring matter that runs along the Milky Way for some 130°, or just over a third of its entire circuit of the sky. The Rift blocks light from the Galaxy beyond, including the regions around the Galactic Core in Sagittarius.
A large and prominent feature of the Milky Way in the sky, the Great Rift forms a dark thread that divides the main band of the Milky Way into two separate strands for about a third of its length. This feature is not truly a 'rift', but a string of dark clouds of dust stretching along the plane of the Galaxy. These immense clouds are some hundreds of light years from the Solar System, and together they obscure the brighter disc and core of the Galaxy that extend out for thousands of light years beyond.
The Rift is not uniformly dark, and examined in detail it reveals rich patterns of internal structure, with tendrils of matter stretching away from the central mass. Structures of this kind are not unique to the Milky Way, and several other spiral galaxies can be observed to show similar patterning, with lanes of dark dust accumulating along their central planes or around their rims.
A detailed view of the Great Rift as it passes through western Sagittarius. This marks the general direction of the Galaxy's core, though the nucleus itself is entirely obscured by the dust of the Rift. The two lighter areas within the dark lane are nebulae: the larger of the two is the Lagoon Nebula, M8, while the smaller object to the north is the Trifid Nebula, M20. Imagery provided by Aladin sky atlas