Scientists were able to determine the position of the planet and its movements in front of its parent star based on the amount of light it blocked. (ibtimes.com)
(A «transit» refers to when the planet appears to pass in front of its parent star as seen from Earth. (seeker.com)
This graphic depicts HD 189733b, the first exoplanet caught passing in front of its parent star in X-rays. (sciencedaily.com)