从可见光扩展到无线电波，再到 X 射线和伽马射线，天文学总是会发现不寻常的物体，如射电星系、类星体和脉冲星。
The extension of astronomy from visible light to radio waves to x-rays and gamma rays never failed to lead to the discovery of unusual objects such as radio galaxies, quasars, and pulsars.
天文学家们发现了一个遥远的星系。
大多数天文学家认为，星系中心的大量物质是一个黑洞，它的引力导致气体旋转。
Most astronomers believe that the large concentration of mass at the galaxy's center is a black hole whose gravity is causing the gas to whirl.
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