The evidence, at first indirect, began to accumulate in 1975: stars and gas tracked in the middle of the galaxy did not follow the orbits they would if the spiral pattern reached all the way in.

• 证据从1975年开始累积，一开始是间接的：位在星系中央的恒星与气体并不遵循单纯的螺旋形状具备的轨道。