When astronomers began searching for extrasolar planets, they were surprised to discover Jupiter-sized planets much closer than 1 AU from their parent stars. Why is this surprising?
A) These planets must have formed at larger radii where temperatures were cooler and then migrated inward.
B) Jupiter-sized, rocky planets were thought to be uncommon in other solar systems.
C) These planets must be the remnants of failed stars.
D) Earth-like planets must be rarer than Jupiter-sized planets in other solar systems.
E) It is different than in our Solar System.

Question

Quizplus · Accepted Answer

According to the nebular theory, gas giants like Jupiter should only form at larger radii where temperatures are cooler, and then migrate inward. Thus, the discovery of Jupiter-sized planets much closer than 1 AU from their parent stars was unexpected and surprising. This led to the idea that these planets must have formed farther out in the protoplanetary disk and then migrated inward to their current orbits.

When Astronomers Began Searching for Extrasolar Planets, They Were Surprised