PTE Multiple Choice, Multiple Answers practice

When an exoplanet orbits a solitary star in complete isolation, its transits across the stellar disc occur at perfectly predictable, periodic intervals. However, if additional celestial bodies inhabit the same planetary system, their mutual gravitational forces exert subtle tugs on the transiting world. These gravitational perturbations cause the transiting planet to accelerate or decelerate slightly along its orbital path, leading to measurable deviations from a strictly uniform schedule. This technique, known as transit timing variation, allows researchers to infer the presence of non-transiting companion planets that would otherwise remain completely invisible to traditional photometric surveys.

Beyond mere detection, transit timing variations yield critical physical data about the interacting worlds. By analysing the amplitude and periodicity of these temporal shifts, astrophysicists can calculate the precise masses of the perturbing planets without relying on radial velocity measurements, which often struggle to resolve low-mass targets around faint stars. Furthermore, the method is particularly sensitive to planets locked in mean-motion orbital resonances, where gravitational interactions are amplified over repeated orbital cycles. Consequently, this analytical approach provides valuable insights into multi-planet system architecture and dynamic orbital evolution over geological timescales.