Astronomers believe that the "hot Jupiters" found orbiting other stars must have migrated inward over time:
A) by slowly accreting large amounts of gas and increasing their gravitational pull
B) by losing their gas due to evaporation
C) by losing orbital angular momentum
D) after colliding with another planet
E) after a close encounter between their star and another star

Question

Quizplus · Accepted Answer

Hot Jupiters are giant planets that orbit very close to their host stars, much closer than Jupiter is to the Sun. It is believed that they could not have formed in these close-in orbits, but must have migrated from their birthplaces further out in the protoplanetary disk. The most likely mechanism for this migration is the loss of orbital angular momentum, which could be caused by interactions with the protoplanetary disk or other planets in the system. This would cause the planet to spiral inward towards its star over time. Accretion of gas, evaporation, collisions, and close encounters between stars are all potential factors that might affect the development of planetary systems, but they are less likely to cause the specific type of migration necessary to produce hot Jupiters.

Astronomers Believe That the "Hot Jupiters" Found Orbiting Other Stars