Final answer:
The method of detecting planets via transits involves measuring the dimming of a star when a planet crosses in front of it. Astronomers observe changes in the brightness of the star over time to determine the orbital period of the planet and measure its size.
Step-by-step explanation:
The method of detecting planets via transits is based on measuring the slight dimming of a star when one of its planets crosses over the face of the star, as seen from Earth. Astronomers observe the change in the brightness of the star over long periods of time. If the dips in brightness repeat at regular intervals, the orbital period of the planet can be determined. Additionally, the amount of starlight obscured during the transit can be used to measure the planet's size.