[extropy-chat] 10th Planet Discovered

[Amara Graps]

Brent Neal:
>You pretty much answered your own question. The orbits of those
>objects, in the opinion of some astronomers seem to be more
>consistent with those of either Oort or Kuiper objects, hence the
>comment.

However, the context was about rocky cores and whether Sedna is a
planet  (? I didn't read all of the thread), so I still don't follow
your 'damning' comment.  The source of Sedna perhaps being from the
Oort cloud doesn't fix its formation origin. While it is true that
the condensation sequence would favor cold icy bodies (argon-neon
ice condenses at 65K, Pluto's temperature, for example), the origin
of these bodies could be, well, almost anywhere.

The bodies in the Oort Cloud probably coalesced among the giant
planets. Jupiter has/had the most influence, but dynamical models by
Levison, Morbidelli and others show that the massive protoplanets
probably all contributed, ejecting bodies inwards and outwards.
Bodies could be 'tossed' (trapped in resonances, until perturbed to
new locations) from giant planet to giant planet like a billiard
game. Because of the diversity of formation locations (scattered
through the giant planets), the composition of the comets are also
diverse. The Oort cloud may even contain asteroids from the inner
planets' region.

People here might have missed another really interesting news item
related to this. In the November 27 Nature, Levison and Morbidelli
showed in their dynamical simulations that the Kuiper Belt objects
could be formed with Neptune, but with Neptune 10 AU closer to the
Sun than it is now (30 AU), and it could 'drag' via energy the
planetesimals, dust and gas with it as its orbit widened. Even more
interesting, is that the current edge of the Kuiper Belt is exactly
at the Neptune 1:2 resonance, which is a very stable place.

Amara
-- 

Amara Graps, PhD
Istituto di Fisica dello Spazio Interplanetario (IFSI)
Istituto Nazionale di Astrofisica (INAF),
Adjunct Assistant Professor Astronomy, AUR,
Roma, ITALIA     Amara.Graps at ifsi.rm.cnr.it