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 are 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 found to date are so close to their stars that their periods are just a few days. This is due to the fact that most planets are detected through the transit method, which requires the planet to pass in front of its star, causing a dip in brightness. Planets that are close to their stars will transit more frequently and be easier to detect, leading to a higher concentration of short-period planets in our current sample. The statement that some extrasolar planets are so close to their stars that their periods are just a few days is true. This is due to the fact that most of these planets have been discovered through the transit method, where the planet passes in front of the star and causes a dip in its brightness, indicating its presence. This method is most effective for planets with short orbital periods, which means they are very close to their star.

Which Statement About Extrasolar Planets Found to Date Is True