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.

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。

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It will remind you of center of mass and all that.

它将来会让你想起质心等等。

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Thomas Wang at the Mass General Heart Center was the senior author of the study.

VOA: special.2009.07.15

The new textbook book was put together by the Documentation Center of Cambodia, a non-profit group tasked with recording the years of mass killing under the Khmer Rouge.

VOA: standard.2010.04.19

Overall, if driven responsibly, a vehicle with all-wheel drive, decent ground clearance and a relatively low center of mass is best, confirms Champion.

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If the computer programming is supple enough and the on-board processing is fast enough, engineers can now virtually nullify effects caused by vehicle height, weight, roll centers and center of mass.

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The specific cause was an epidural medication for back pain produced by the New England Compounding Center of Framingham, Mass.

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