Question

If astronomers were to find they have made a mistake and our solar system is actually 7.2 (rather than 8.2) kpc from the center of the galaxy, but the orbital velocity of the sun is still 240 km/s, what is the minimum mass of the galaxy?

Answer 1

Assuming a circular orbit for the Sun, we can use the equation:

v^2 = GM/r

where v is the orbital velocity of the Sun, r is the distance from the center of the galaxy, G is the gravitational constant, and M is the mass of the galaxy.

We can solve for M:

M = v^2 * r / G

Using the given values of v = 240 km/s and r = 7.2 kpc = 7.2 * 3.086e+19 m, and G = 6.6743e-11 N m^2/kg^2, we get:

M = (240000 m/s)^2 * 7.2 * 3.086e+19 m / 6.6743e-11 N m^2/kg^2

M = 1.47e+42 kg

Therefore, the minimum mass of the galaxy, if the distance of the solar system from the center is actually 7.2 kpc, is approximately 1.47 x 10^42 kg.