If you detect an exoplanet that is orbiting a star that is 8 times as massive as the Sun with an orbital period of 1 (Earth) year, you would expect the semimajor axis of its orbit to be
A) 8 AU.
B) 6 AU.
C) 4 AU.
D) 2 AU.
E) 1 AU.

Question

Quizplus · Accepted Answer

According to Kepler's third law, the square of the orbital period (T) is proportional to the cube of the semimajor axis (a) divided by the mass of the star (M). For a star 8 times the mass of the Sun, the semimajor axis a = (T^2 * M)^(1/3) = (1^2 * 8)^(1/3) = 2 AU.

If You Detect an Exoplanet That Is Orbiting a Star