The Challenge of Sedna

Sedna is the most distant world known in our Solar System. It is now about 90 times farther away from the Sun than the Earth (90 astronomical units or AU). Unlike the Earth, Sedna follows a highly elliptical path around the Sun. At its closest approach, Sedna is 70 AU away from the Sun. When it is most distant, it is more than 1000 AU away! Shuttling back and forth between 70 AU and 1000 AU, Sedna takes more than 10,000 years to orbit the Sun.

Sedna is a challenge to current theories of planet formation. When planets first form, they have circular orbits around their parent stars. Gravitational forces between planets produce elliptical orbits. In the Kuiper Belt, Neptune's gravity produces the Plutinos, twotinos, and scattered KBOs. However, Neptune is too far away from Sedna to make Sedna's elliptical orbit.

We used numerical simulations to try to understand why Sedna's orbit is so elliptical. Not only were we able to produce objects with Sedna-like orbits, our results suggest that Sedna might be the nearest extrasolar planet!

The links below have some background for orbits in the Solar System and then describe our recipe for making Sedna-like orbits.

KBO orbits
Sedna's orbit
Making Sedna's orbit
Testing the model

Sedna may be the closest extrasolar planet.
View the animation...