Astronomers estimate that there may be a trillion (a thousand billion) comet nuclei orbiting beyond Pluto. Why then do we not see more comets in our skies?
A) most comets are so small that millions pass by the Earth completely undetected
B) most comets have orbits that only bring them inward as far as the orbit of Jupiter
C) most comets collide with Jupiter each year and are thus not seen
D) most comets remain in stable orbits beyond Pluto, only a few have their orbits disturbed and come into the inner solar system
E) all the comets astronomers miss are the reason so many people report seeing UFO's

Question

Quizplus · Accepted Answer

Most comets remain in stable orbits beyond Pluto, only a few have their orbits disturbed and come into the inner solar system. This means that while there may be a large number of comet nuclei in the outer solar system, they don't necessarily all become comets that we can see from Earth.

Astronomers Estimate That There May Be a Trillion (A Thousand