In an exoplanet system in which a gas giant has an orbit very close to its star, how commonly have astronomers found other planets at larger orbital distances from the star?
A) extremely rarely, because the migrating gas giant drives all the other planets into the star
B) extremely rarely, because the migrating gas giant ejects all the other planets from the system
C) extremely rarely, because the existence of a close-in gas giant implies that all the available material was accreted onto that planet
D) in about half of such exoplanet systems

Question

Quizplus · Accepted Answer

In about half of the exoplanet systems where a gas giant orbits very close to its star, astronomers have found other planets at larger orbital distances. This suggests that the presence of a close-in gas giant does not preclude the existence of other planets further out in the system.

In an Exoplanet System in Which a Gas Giant Has