Which statement about extrasolar planets found to date is true?
A) All are terrestrials, comparable in size to Earth.
B) Few are found by Doppler shifts of their stars, due to their gravity.
C) All lie more than 2 A.U. from their star.
D) Most have orbital periods of more than a year.
E) Some are so close to their stars that their periods are just a few days.

Question

Quizplus · Accepted Answer

Some extrasolar planets are so close to their stars that their periods are just a few days. This is due to the fact that most have been found using the transit method, where a planet passing in front of its star causes a dip in the star's brightness, which can only be detected if the planet is close enough and has a short orbital period. Therefore, option E is the correct statement. The other statements are false.

Which Statement About Extrasolar Planets Found to Date Is True