If you found an exoplanet whose mass was the same as Jupiter's, but the planet orbited its star with a period of 2 years and a semimajor axis of 1 AU, what would be the mass of its star? For reference, Jupiter has a semimajor axis of 5.4 AU and an orbital period of 12 years. A) 0.25 M _$\odot$ B) 0.5 M _$\odot$ C) 2.0 M _$\odot$ D) 1.5 M _$\odot$ E) not enough information available to answer

Question

Quizplus · Accepted Answer

Kepler's Third Law states that the square of the orbital period of a planet is proportional to the cube of the semimajor axis of its orbit. In this case, the planet has the same mass as Jupiter, but its orbital period is 2 years and its semimajor axis is 1 AU. Jupiter has an orbital period of 12 years and a semimajor axis of 5.4 AU. Therefore, the mass of the star must be 0.25 times the mass of the Sun.

If You Found an Exoplanet Whose Mass Was the Same ⊙\odot⊙

If You Found an Exoplanet Whose Mass Was the Same $\odot$