There’s Another Sedna!

Image credit: Scott Sheppard - Orange: Sedna's orbit, Red: 2012 VP113 orbit
Image credit: Scott Sheppard – Orange: Sedna’s orbit, Red: 2012 VP113 orbit

This is indeed an exciting find, and I congratulate Chad Trujillo and Scott Sheppard on their discovery.  I wrote the Nature News &  Views article about what the paper and discovery. The orbit of 2012 VP113 never gets closer to the Sun than 80 AU and has its furthest distance from the Sun at  452 AU . Like Sedna which was discovered a decade ago, this orbit is unexplainable with what we know about the current state of the Solar System.  Sedna and the new discovery are too far away from the giant planets to feel its gravitational effects. These objects are too far away from the edge of the solar system to feel the effects of passing stars and the effects of the rest of the Galaxy like objects in the  Oort cloud (the reservoir of long period comets) do. Galactic tides and gravitational nudges from passing stars in the current solar environment, can perturb objects in the Oort cloud and send them in on orbits towards the inner Solar System as comets, but  Sedna and this new discovery are effectively cut off from the rest of the solar system.  Something else earlier on in the history of the Solar System had to put them on these orbits.

When Sedna was discovered several theories were put forth to explain its extreme orbit (and now to explain 2012 VP113) including interactions with planet-sized bodies, multiple stellar fly-bys in a stellar birth cluster, interstellar capture, and perturbations from a wide-binary solar companion. Each proposed scenario creates a population of icy bodies beyond the Kuiper belt and leaves a distinctive imprint on the orbits of these distant objects that would be still be observable today. With one or two objects, we  can’t uniquely identify the formation mechanism for the inner Oort cloud, but Trujillo and Sheppard find that the orbits of 2012 VP113 and Sedna are consistent with models for the Sun’s birth cluster and previous constraints on the cluster model from other ground-based, wide-field surveys.

There have been other candidate objects discovered in the past that might have a Sedna-like orbit, but with 2012 VP113 never approaching more than 80 AU from the Sun, its status as a member of the inner Oort Cloud is concrete. It is thrilling that we definitely know there are more objects like Sedna out on these distant orbits far from the Sun. With 8-10-meter class telescopes coming online equipped now in the next decade with large fields-of-view (such as the Subaru Telescope with Hyper Suprime-Cam and the Large Synoptic Survey Telescope), I think we’ll be able to find many more residents of the inner Oort Cloud, and begin to really study this population of remote icy bodies that until now has remained rather elusive.


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