If the only force exerted on a star far from the center of the Galaxy (r = 7.40 ✕ 1020 m) is the gravitational force exerted by the ordinary matter (Mord = 1.90 ✕ 1041 kg), find the speed of the star. Assume a circular orbit and assume all the Galaxy's matter is concentrated at the center.

The value is  

Explanation:

The radius is

The mass of the ordinary matter is

Generally the speed of the star is mathematically represented as

Here G is the gravitational constant with a value

So

=>    

what is the question because that is not a question.

3. dark matter

empty space could also be a simple vacuum