This structure, which is the second-largest member of the (*)  Local Group, is orbited by the Large and Small Magellanic Clouds.
In a coordinate system devised by the IAU in 1958, the distribution of neutral hydrogen emissions was used to determine the "equator" of this structure. The exact number of globular clusters in this structure cannot be precisely known because some of them are obscured by this structure's "Zone of Avoidance." Harlow Shapley argued that "spiral nebulae" were merely extensions of this structure during the "Great Debate" with Heber Curtis. This structure, which is the second-largest member of the (*)  Local Group, is orbited by the Large and Small Magellanic Clouds. A supermassive black hole sometimes called Sagittarius A-star lies at the center of this structure, which will eventually collide with Andromeda. For 10 points, name this galaxy, whose planets include Earth.
In a coordinate system devised by the IAU in 1958, the distribution of neutral hydrogen emissions was used to determine the "equator" of this structure.
Milky Way