Question

If a planet was located approximately 25 thousand light-years from the center of a galaxy and orbits that center once every 247 million years, how fast is the planet traveling around the galaxy in km/hr? If needed, use 3.0 × 10^8 m/s for the speed of light.

Answer 1

The distance of the planet from the centre i.e. radius,

`r=25000\text{ light years}`

The time period is

`T=247\text{ million years}`

The speed of the planet is given by the formula

`v=(2\pi r)/(T)`

Substituting the values, the speed will be

`\begin{gathered} v=\frac{2*\pi*25000\text{ }*9.461*10^(12)}{247*10^6*876} \\ =6.866*10^5\text{ km/hr} \end{gathered}`