Sedna Proves Oort Cloud?

I just read in SFGate that the newly discovered planetoid, Sedna, is
the first direct evidence of the Oort Cloud. There was also some blurb
about Sedna likely to have been pulled out of the Kuiper Belt by
receeding stars.

"The new discovery is the first hard evidence of an Oort Cloud object,
[Michael E.] Brown said.

"Sedna must have been one of millions of objects within the Kuiper
Belt but was flung out of that region by the gravitational pull of
other stars in the cluster that were moving outward in nearby areas of
the galaxy."

"Farthest object in sun's grip found: Sedna's 10,000-year solar orbit
proves existence of Oort Cloud, scientist says"
http://sfgate.com/cgi-bin/article.cg.../16/PLANET.TMP

How is Sedna evidence of the Oort Cloud, particularly if it came from
the Kuiper Belt? Does it even make sense to talk about distance stars
"flinging" objects out of the Kuiper Belt?

In article ,
"Mike Dworetsky" writes:
I doubt if a passing star had anything to do with flinging this object
anywhere.

I think the idea is that if the object was created in the inner solar
system and flung out by interaction with, say, a proto-Jupiter, you
need an interaction with passing stars to raise the perihelion.

The discoverer's web page, cited in another thread,
http://www.gps.caltech.edu/~mbrown/sedna/
is quite good.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
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(Steve Willner) wrote in
:

I think the idea is that if the object was created in the inner solar
system and flung out by interaction with, say, a proto-Jupiter, you
need an interaction with passing stars to raise the perihelion.

Don't forget that brown dwarves have recently been found to be wandering
between the stars, supposedly the same territory occupied by the Oort
cloud. And Sedna, Quaoar and Pluto are all fairly large by the standards
of "planetoids," and are quite capable of causing large angle scattering
events without making a head on collision.

There is no reason to believe that there is not a fairly large,
undiscovered population of like-sized planetoids out there, all having
comparatively frequent, large angle scattering events with each other, and
thereby throwing each other into orbits of high eccentricity. This is
completely unknown territory, and the old argument of wandering stars
causing gravitational perturbations has to be completely revised in light
of all these new discoveries.

Or as Bill Clinton might say, "That old dog just don't hunt no more."

In article ,
John Schutkeker writes:
Don't forget that brown dwarves have recently been found to be wandering
between the stars, supposedly the same territory occupied by the Oort
cloud.

You might want to check just what space density is implied by the
observations. How near do we expect the nearest brown dwarf to be?

And Sedna, Quaoar and Pluto are all fairly large by the standards
of "planetoids," and are quite capable of causing large angle scattering
events without making a head on collision.

How close would an object have to come to one of these to be
scattered through a large angle? How does that compare to the
estimated radius of Sedna or Quaoar? Or use Pluto if you prefer; at
least its size and mass are well known.

There is no reason to believe that there is not a fairly large,
undiscovered population of like-sized planetoids out there, all having
comparatively frequent, large angle scattering events with each
other,

If you put in a reasonable limit on total mass of such a population,
how many planetoids would there be? Given the resulting space
density and known velocities, how often would each object experience
a large-angle scattering?

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
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Jeez, I thought you Harvard guys were supposed to answer the hard questions
as well as simply asking them. Would you care to suggest a couple of
references so that I can get started researching the answers? I always
prefer to see if somebody else has worked out the solutions before I try to
do them myself.

(Steve Willner) wrote in
:

In article ,
John Schutkeker writes:
Don't forget that brown dwarves have recently been found to be
wandering between the stars, supposedly the same territory occupied
by the Oort cloud.

You might want to check just what space density is implied by the
observations. How near do we expect the nearest brown dwarf to be?

And Sedna, Quaoar and Pluto are all fairly large by the standards
of "planetoids," and are quite capable of causing large angle
scattering events without making a head on collision.

How close would an object have to come to one of these to be
scattered through a large angle? How does that compare to the
estimated radius of Sedna or Quaoar? Or use Pluto if you prefer; at
least its size and mass are well known.

There is no reason to believe that there is not a fairly large,
undiscovered population of like-sized planetoids out there, all
having comparatively frequent, large angle scattering events with
each other,

If you put in a reasonable limit on total mass of such a population,
how many planetoids would there be? Given the resulting space
density and known velocities, how often would each object experience
a large-angle scattering?

[I haven't seen any responses to this, so even though my reply is a
bit dated....]
"JS" == John Schutkeker writes:

JS Would you care to suggest a couple of references so that I can get
JS started researching the answers? I always prefer to see if
JS somebody else has worked out the solutions before I try to do them
JS myself.

JS (Steve Willner) wrote in
JS :

In article , John
Schutkeker writes:
Don't forget that brown dwarves have recently been found to be
wandering between the stars, supposedly the same territory
occupied by the Oort cloud.

You might want to check just what space density is implied by the
observations. How near do we expect the nearest brown dwarf to be?

As usual, ADS is your friend. A quick search of "solar AND
neighborhood AND brown AND dwarf" found a paper by Cruz et al. (2003,
URL:
http://adsabs.harvard.edu/cgi-bin/np...J....126.2421C
). I think if you do a Web search, you'll also find RECONS and a
couple of other programs dedicated to taking a census of the solar
neighborhood.

From the Cruz et al. paper, it appears that there are something like
220 stars or brown dwarfs later than spectral type M6 within 25 pc.
Crudely, that suggests that the typical distance between brown dwarfs
is something like 5 pc.

And Sedna, Quaoar and Pluto are all fairly large by the standards
of "planetoids," and are quite capable of causing large angle
scattering events without making a head on collision.

How close would an object have to come to one of these to be
scattered through a large angle? How does that compare to the
estimated radius of Sedna or Quaoar? Or use Pluto if you prefer;
at least its size and mass are well known.

This is a freshman (well, maybe sophomore) physics problem. Start
with Newton's universal law of gravitation and use conservation of
momentum and energy.

There is no reason to believe that there is not a fairly large,
undiscovered population of like-sized planetoids out there, all
having comparatively frequent, large angle scattering events with
each other,

If you put in a reasonable limit on total mass of such a
population, how many planetoids would there be? Given the
resulting space density and known velocities, how often would each
object experience a large-angle scattering?

Check Luu & Jewitt (2002, URL:
http://adsabs.harvard.edu/cgi-bin/np...%26A..40...63L
) for a recent review article on the Kuiper Belt.

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