We have more comets at the outer edges of our solar system than we should. Find out how our sun came out the winner in an interstellar game of keep-away.
Out beyond Pluto, a cloud of comets orbits our sun. Up until now it was thought that the Oort cloud was the natural detritus left over from the formation of the planets. The pieces of debris were circling the sun along with the big boys, like earth and Jupiter, until the central planets kicked them out. It seemed the most logical scenario, until scientists, when counting up the objects in the Oort cloud, ran across a problem. The current theory of the Oort cloud's formation provided for about 6 million objects. Looking at the Oort cloud, scientists estimated that it was populated by around 400 billion pieces of matter.
Hal Levison, a researcher at the Southwest Research Institute, came up with another theory. What if the Oort cloud had been formed a lot earlier than was originally assumed? What if it had been formed in the same massive gas cloud that had birthed the sun?
According to Levison, the Oort cloud resulted from early stars swapping material.
"We know that stars form in clusters. The Sun was born within a huge community of other stars that formed in the same gas cloud. In that birth cluster, the stars were close enough together to pull comets away from each other via gravity. It's like neighborhood children playing in each others' back yards. It's hard to imagine it not happening."
The cluster dispersed, separating the sun from its brethren. But it didn't go alone. The Oort cloud, with its wealth of comets, came along for the ride. Our sun's thievery may have significantly enriched our night sky. Who says crime doesn't pay?