If the Rotational Speed of the Gas in the Disk

question 33

Multiple Choice

If the rotational speed of the gas in the disk of a spiral galaxy is 200 km/s at a distance of 25,000 pc from its center,then what is the mass enclosed within this radius?

• A)7.5 billion M_⨀
• B)18 billion M_⨀
• C)70 billion M_⨀
• D)230 billion M_⨀
• E)400 billion M_⨀

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