You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?
A)The planet must have a mass about the same as the mass of Jupiter.
B)The planet must be closer to the star than Earth is to the Sun.
C)You do not have enough information to say anything at all about the planet.
D)The planet must be farther from the star than Neptune is from the Sun.

Question

Quizplus · Accepted Answer

The periodic back-and-forth motion of the star, observed once every 4 months, suggests that the planet has a short orbital period, indicating it is closer to its star than Earth is to the Sun. This is because the gravitational interaction between the star and the planet, causing the observed motion, depends on the distance between them, with closer planets exerting a stronger influence that leads to shorter orbital periods.

You Observe a Star Very Similar to Our Own Sun