From the Oort Cloud?
Sedna is thought to dwell in the inner, sunward regions of the Oort cloud, a cloud of chunks of ice and freezing cold worldlets that’s believed to be the origin of comets. If so, Sedna is the first object ever observed in the Oort cloud, whose existence till now has only been hypothetical. Comets arise when, from time to time, something knocks one of these ice bodies out of their orbit and sends it hurtling in toward the Sun. The same sort of phenomenon -- maybe a runaway star or planet? -- probably caused Sedna’s strange, elliptical orbit as well. Scientist also speculate that companion stars to the Sun, present during its birth, could have caused Sedna to take up the orbit she now has. Such a theory means that the Sun was part of a cluster of newborn stars that drifted away from each other over eons and probably formed their own stellar systems. This has great implications for scientists' understanding of how our Solar System was formed and why Sedna is an important object in the solar system. What if the Sun hadn't been born alone but had siblings? Where are they? What happened to them? Are they still influencing our Solar System?
It’s also possible that Sedna isn’t of our Solar System at all, but was captured by the Sun’s gravity from another stellar system passing through the Sun’s neighborhood. Other scientists blame Sedna’s orbit on an as yet undiscovered stellar companion of the Sun called Nemesis, but there’s no indication that Nemesis exists. Others believe that her orbit is the result of the disturbance caused by the gravity of an unknown planet between 1,000 and 5,000 AU’s out from the Sun, but as with Nemesis, this planet hasn’t been found.
At her closest Sedna is about 75 AU or Astronomical Units from the Sun. An Astronomical Unit is the distance Earth is from the Sun, which is about 93 million miles. Because of this, scientists now wonder if the Oort cloud, at first believed to be extremely far out in the Solar System, perhaps even as much as a light year, is closer than was once thought. Sedna will be at her closest to Earth in about 72 years. But she’ll still be extremely far from us.