Question
Imagine an astronomer is studying a distant galaxy and observes a planet orbiting a star. The orbit is slightly different than expected. What might be causing this unexpected orbital motion? Discuss one possibility.(2 points)
Answers
GPT-5 mini
One simple possibility is a gravitational perturbation from an unseen companion (another planet, a distant massive planet, or a faint binary star). In a real system the planet-star pair is not an isolated two-body problem: additional masses exert time-varying forces that change the planet’s orbital elements (period, eccentricity, inclination and the orientation of the orbit). This can produce precession of the orbit, periodic deviations from the expected position or transit times, or long-term drift.
How you would tell: the perturbation often shows up as periodic transit-timing variations or small extra signals in the star’s radial velocity curve. Modeling the deviations can constrain the mass and orbit of the unseen perturber.
How you would tell: the perturbation often shows up as periodic transit-timing variations or small extra signals in the star’s radial velocity curve. Modeling the deviations can constrain the mass and orbit of the unseen perturber.