First hypothesized by Dutch astronomer Jan Hendrik Oort in 1950, the Oort Cloud is a spherical field which is the source of long-term comets.
No Oort Cloud bodies have ever been seen, as they are so small and far away, but now scientists believe that Sedna might be the first finding, particularly as it has an extremely elliptical orbit.
However the cloud has been thought of as starting at least 5,000 AU away from the sun and extending half way to the next star , while Sedna is only at a distance of about 76-850AU.
Dr Mike Brown, the discoverer of Sedna, addressed this issue by positing an ‘inner Oort cloud’ caused by a ‘rogue star’ in the early days of the solar system which dislodged comets from the outer belt.
However there has been much disagreement on this issue, with other scientists describing the body as a ‘scattered disc’ object or arguing that is a particularly far-flung member of the Kuiper belt of trans-Neptunian objects.