What is the most likely reason that there are no giant planets beyond Neptune?
A)Any planets forming beyond Neptune would have drifted out of the solar system due to the weakness of the Sun's gravity at this distance.
B)There was no material to create planetesimals beyond the orbit of Neptune.
C)By the time planetesimals grew to a large enough mass to hold onto an atmosphere,the solar nebula had been blown away.
D)Any planet forming beyond Neptune's orbit would have been scattered outside of the solar system by gravitational encounters.
E)There may be,but they would be so faint that astronomers have not found them yet.

Question

Quizplus · Accepted Answer

The solar nebula, the cloud of gas and dust from which the solar system formed, had dissipated by the time planetesimals grew to a size large enough to hold onto an atmosphere. Therefore, it is unlikely that giant planets could have formed beyond Neptune.

Answer: D
 Gravitational encounters with other massive bodies in the early solar system may have scattered any potential giant planets beyond Neptune's orbit out of the solar system entirely. Such encounters could have been common early on when the solar system was still forming.

What Is the Most Likely Reason That There Are No