Question

Let us assume that our galaxy consists of 2.5 × 10¹¹ stars each of one solar mass. How long will a star at a distance of 50,000 ly from the galactic centre take to complete one revolution? Take the diameter of the Milky Way to be 10⁵ ly.

Answer 1

Mass of our galaxy Milky Way, M = 2.5 x 10¹¹ solar mass

Solar mass = Mass of Sun = 2.0 x 10³⁶ kg

Mass of our galaxy, M = 2.5 x 10¹¹ x 2 x 10³⁶ = 5 x10⁴¹ kg

Diameter of Milky Way, d = 10⁵ ly

Since a star revolves around the galactic centre of the Milky Way, its time period is given by the relation: