Question

The Sun rotates around the center of the Milky Way Galaxy (the figure below (Figure 1)) at a distance of about 30,000 light-years from the center (1ly=9.5×1015m). 1.If it takes about 200 million years to make one rotation, estimate the mass of our Galaxy. Assume that the mass distribution of our Galaxy is concentrated mostly in a central uniform sphere. Express your answer using one significant figure. 2.If all the stars had about the mass of our Sun (2×1030kg), how many stars would there be in our Galaxy? Express your answer using one significant figure.

1.

If it takes about 200 million years to make one rotation, estimate the mass of our Galaxy. Assume that the mass distribution of our Galaxy is concentrated mostly in a central uniform sphere.

Express your answer using one significant figure.

2.

If all the stars had about the mass of our Sun (2×1030kg), how many stars would there be in our Galaxy?

Express your answer using one significant figure.

Answer 1

Answer:

a) Mass of our galxy

b) Number of stars that can be occuppied in our galaxy = stars

Explanation:

a) We have gravitational force = and centripetal force =

Equating both of them

Mass of galaxy,

Distance from center, r = 30,000 light-years =

Circumference =

Period = 200 million years =

So velocity,

   Mass of galaxy,

So mass of our galxy

b) The mass of sun is given by

Mass of our galxy

Number of stars in the galaxy = stars.

So number of stars that can be occuppied in our galaxy = stars