Question

The star Rho1 Cancri is 57 light-years from the earth and has a mass 0.85 times that of our sun. A planet has been detected in a circular orbit around Rho1 Cancri with an orbital radius equal to 0.11 times the radius of the earth's orbit around the sun. What are (a)the orbital speed and (b)the orbital period of the planet of Rho1 Cancri

Answer 1

82780.42123 m/s

14.45 days

Step-by-step explanation:

m = Mass of the planet

M = Mass of the star =
`0.85* 1.989* 10^(30)\ kg`

r = Radius of orbit of planet =
`0.11* 149.6* 10^(9)\ m`

v = Orbital speed

The kinetic and potential energy balance is given by

`(GMm)/(r^2)=(mv^2)/(r)\\\Rightarrow v=\sqrt{(Gm)/(r)}\\\Rightarrow v=\sqrt{(6.67* 10^(-11)* 0.85* 1.989* 10^(30))/(0.11* 149.6* 10^(9))}\\\Rightarrow v=82780.42123\ m/s`

The orbital speed of the star is 82780.42123 m/s

The orbital period is given by

`t=(2\pi r)/(v)\\\Rightarrow t=(2\pi * 0.11* 149.6* 10^(9))/(82780.42123)\\\Rightarrow t=1249040.48419\ seconds=(1249040.48419)/(24* 60* 60)=14.45\ days`

The orbital period is 14.45 days