The reason that most extrasolar planets are found close to their parent stars is
A) the planets reflect more light the closer they are to the star.
B) more of the starlight is blocked by the planet when it transits the star.
C) the Doppler shift of the star's spectrum is larger.
D) the closer to a star, the hotter and therefore brighter the planet is.
E) planets that are close to a star are heated up and therefore larger.

Question

Quizplus · Accepted Answer

Most extrasolar planets are detected using the radial velocity technique, which relies on detecting the wobbling motion of a star caused by the gravitational pull of its orbiting planets. This wobbling motion causes a Doppler shift in the star's spectrum, which can be measured by observatories on Earth. The larger the planet, the greater the gravitational pull it exerts on the star, and the larger the wobbling motion and resulting Doppler shift. However, this method is most effective for planets that are close to their stars, since they exert a stronger gravitational pull and cause a larger Doppler shift in a shorter period of time. Therefore, most extrasolar planets that have been discovered to date are "hot Jupiters," gas giant planets that orbit very close to their stars (sometimes closer than Mercury orbits our Sun).

The Reason That Most Extrasolar Planets Are Found Close to Their