How do we know the total mass of the Milky Way Galaxy that is contained within the Sun's orbital path?
A) By applying Newton's version of Kepler's third law (or the equivalent orbital velocity law) to the Sun's orbit around the center of the Galaxy
B) By counting the number of stars visible in this region of the galaxy
C) By estimating the amount of gas and dust in between the stars
D) By using the law of conservation of angular momentum to calculate the orbital speeds of nearby stars

Question

Quizplus · Accepted Answer

We can use Newton's version of Kepler's third law (or the equivalent orbital velocity law) to calculate the mass of the Milky Way Galaxy that is contained within the Sun's orbital path. This is because the mass of the galaxy, as well as the distance of the Sun from the center of the galaxy, influence the way the Sun orbits the galaxy. By measuring the Sun's speed and radius of its orbit, we can calculate the mass of the galaxy within that orbit.

How Do We Know the Total Mass of the Milky