What is the Oort cloud and what is its relationship to Sedna?
The Oort cloud is a hypothetical shell of icy proto-comets in very loose orbits around the sun that extends to a distance of almost halfway to the nearest star. Occasionaly, passing stars cause a slight change in the orbit of one of these proto-comets which causes them to come steaking in to the inner solar system where we see them as comets. A nice explanation can be found here. Though the Oort cloud has never been seen directly, the comets that we do see are very strong evidence of its existence. As can be seen in the graphic above, though, the Oort cloud is expected to be much much further out than the orbit of Sedna. So why do we think Sedna is a member of the Oort cloud? We believe that the existence of Sedna is evidence that the Oort cloud actually extends much further in towards the sun than previously thought. This “inner Oort cloud” was formed in the same manner as the previously known “outer Oort cloud.” Early in the history of the solar system many many small icy bodies were
