How do you calculate a planet's period based on its orbit/AU from the sun?

For instance, An asteroid is in circular orbit 4 AU from the Sun. What is the period of the asteroid in years?


How would I solve this???|||Newton's version of Kepler's third law tells you that


d[AU]^3 = P[years]^2.





So in this case P = 4^(3/2) = 8 years.|||p^2=a^3 where a is the semi major axis of the orbit in AU and p is the period in years. In this case the orbit is circular so the semi major axis is just the radius of the orbit. So p=sqrt((4 AU)^3)=8 years