The Origin of Sedna's Orbit

How did Sedna end up in its current orbit? The simulation sedna.gsim attempts to reproduce an experiment performed by Alessandro Morbidelli and Harold F. Levison designed to explain the origin of Sedna's (2003 VB12) highly elliptical orbit.

Sedna was discovered in 2003 by a team of astronomers consisting of Mike Brown, Chad Trujillo, and David Rabinowitz. Shortly after its discovery, it was realized that Sedna has a very elliptical orbit that carries it far from the Kuiper Belt, about 90 Astronomical Units (AU) from the Sun into the hypothisized Oort Cloud. At its farthest, Sedna is about 900 AU from the Sun. It takes over 10,000 years for Sedna to complete one orbit of the Sun.

Astronomers Alessandro Morbidelli and Harold F. Levison investigated Sedna's origins by performing numerical integrations using the Swift_rmvs3 orbit integrator to explore the idea that Sedna may have once been gravitationally bound to another star or brown dwarf, and stripped from that other star by the Sun, where it entered a highly eccentric orbit.

Using Gravity Simulator, I reproduced their experiment. Morbidelli and Levison set up the following starting conditions: The visiting brown dwarf has a mass of 0.05 solar masses. It is has a velocity of 1 km/s relative to the Sun at infinity. Its approach distance to the Sun is 200 AU. The brown dwarf has a disk of test particles orbiting it in random distances between 20-100 AU.

The green planet around the Sun represents the orbit of Neptune. It is just there to give you a sense of perspective of the solar system's size.

In Morbidelli and Levison's experiment, 44% of the Brown Dwarf's objects were captured into Solar orbit. In Gravity Simulator, consistant with Morbidelli and Levison's experiment, 8 of 20 objects were captured into Solar orbit.

Download sedna.gsim

(You need to have the program Gravity Simulator installed on your computer first. Click Here to download Gravity Simulator.)

As the simulation begins, the Brown Dwarf system is closing in on the Solar System from a distance of just under 1 trillion kilometers.

The Brown Dwarf system closes its distance to the Sun. The green planet around the Sun is Neptune.

As the Brown Dwarf system gets even closer, the Sun's gravity starts distorting the system.

The Sun sends a strong gravitational tidal force through the Brown Dwarf system. Objects outside the Brown Dwarf's Hill sphere are stripped away. Some enter a Solar orbit.

After all the dust has settled, 8 objects which originally orbited the Brown Dwarf are now orbiting the Sun, some in Sedna-like orbits.