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MCQIntermediateGalaxies & Extragalactic Astronomy
USAAAO — 2016 First Round
Question 5
Estimate the minimum mass of a galaxy with a radius of 40,000 ly if stars at the edge of the galaxy orbit with a velocity of 50 km/s. Assume there is no dark matter in the galaxy. Answers are given in solar masses, with 1 solar mass = 1.99*10³⁰ kg.
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Source
Source: USAAAO 2016 First Round, Question 5. The official answer key marks option B; the numerical inputs merit review before publication.