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astronomers have recently observed stars orbiting at very high speeds around an

ID: 1769075 • Letter: A

Question

astronomers have recently observed stars orbiting at very high speeds around an unknown object near the center of our galaxy. for stars orbiting at distances of about 10^14 m from the object, the orbital velocities are about 10^6 m/s. assume the orbits are circular, and estimate the mass of the object, in units of the mass of the sun (Msun=2x10^30 kg). if the object was a tightly packed cluster of normal stars, it should be a very bright source of light. since no visible light is detected coming from it, it is instead believed to be a suppermassive black hole.

Explanation / Answer

Attractive force would provide necessary centripetal force to go in circle

Attracticve force = (G * m1 * m2)/ r^2

(G * m1 * m2)/ r^2 = m2*v^2 /r

6.67 * 10^(-11) * m1 = 10^12 * 10^14

m1 = 1.5 * 10^36

m1/ M sun = 1.5 * 10^36 / 2 * 10^30

m1 = 750000 M_sun