posted by Reese .
Halley’s comet orbits the Sun with a period of 76.2 years.
a) Find the semi-major axis of the orbit of Halley’s comet in astronomical units (1 AU is equal to the semi-major axis of the Earth’s orbit
There is a simple form of Kepler's Third law for objects orbiting the sun.
If the period P is in years and the semimajor axis a is in a.u.,
P^2 = a^3
You know that P = 76.2 yr
Solve for a