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No Really Big Worlds Beyond The Kuiper Belt?
ljk4-1
post Oct 17 2005, 12:53 AM
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No Kuiper Belt Jupiters; No Nemesis

Astronomers have long wondered whether the solar system might have an
unseen giant planet far out in the darkness beyond Pluto and the Kuiper
Belt. If so, it must be very far out indeed.

Nadia Zakamska and Scott Tremaine have set new limits on the existence
of any such massive object.... Earlier this year, Varun Bhalerao and M. N.
Vahia showed that no red-dwarf companion of the Sun (a so-called "Nemesis"
object) can exist within 25,000 astronomical units....

http://SkyandTelescope.com/news/article_1609_1.asp


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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abalone
post Oct 17 2005, 10:14 AM
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QUOTE (ljk4-1 @ Oct 17 2005, 11:53 AM)
No Kuiper Belt Jupiters; No Nemesis

Astronomers have long wondered whether the solar system might have an
unseen giant planet far out in the darkness beyond Pluto and the Kuiper
Belt. If so, it must be very far out indeed.

Nadia Zakamska and Scott Tremaine have set new limits on the existence
of any such massive object.... Earlier this year, Varun Bhalerao and M. N.
Vahia showed that no red-dwarf companion of the Sun (a so-called "Nemesis"
object) can exist within 25,000 astronomical units....

http://SkyandTelescope.com/news/article_1609_1.asp
*

Very interesting info, answers a lot of questions raised in another thread . Thanks
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blobrana
post Oct 17 2005, 12:23 PM
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Hum,
Cool,
yesterday’s news, brought to you today.
No Nemesis no planet X

http://au.arxiv.org/PS_cache/astro-ph/pdf/0506/0506548.pdf
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Guest_Richard Trigaux_*
post Oct 17 2005, 03:14 PM
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Guests






If we read the paper, we find that the accuracy of their work is the detection of 1 Jupiter mass at 200 AU (30 billion kms, 5 times the distance of Pluton). This rules out star-sized bodies at short distance, but still allows for many surprises, such as Jupiter-sized objets at a great distance. If we assume that the effect of the Sun follows a 1/R2 law, at 0.1 light year we could still have 1000 Jupiter mass, or the mass of the Sun. At less than 0.2 light years a small black hole can still hide into the error box.

More realistically we can say:

-This study does not rule out Jupiter sized bodies in the far solar system, especially if they are many (in a belt) or a cloud of gaz in orbit or close vicinity.

-we are still far from detecting the effect of neighbouring stars. A 1000 more resolution would be necessary to detect the effect of Proxima centauri.


This study brings matter for the study of the Pioneer anomaly, or for the study of the anomalies in the cosmic background radiation. (there is an assymettry in this background, which seems related to the solar sytem)
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blobrana
post Oct 17 2005, 09:32 PM
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QUOTE (Richard Trigaux @ Oct 17 2005, 07:44 PM)
More realistically we can say:

-This study does not rule out Jupiter sized bodies in the far solar system.


Indeed,
but I wonder how stable those very distant orbits would be, (in the long term), given that passing stars come quite close by every few million years.

I imagine that in a time scale of a few hundred million years, most would be flung out of our system
(er, on the other hand, the sun may acquires new ones)...
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Guest_Richard Trigaux_*
post Oct 18 2005, 07:31 AM
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Guests






QUOTE (blobrana @ Oct 17 2005, 09:32 PM)
Indeed,
but I wonder how stable those very distant orbits would be, (in the long term), given that passing stars come quite close by every few million years.

I imagine that in a time scale of a few hundred million years, most  would be  flung out of our system
(er, on the other hand,  the sun may acquires new ones)...
*


Yes there is surely some kind of outer limit to the solar system, because of this. But until now we have no idea of it. So between this unknown outer limit and what we know for sure, there is still place for many expectation and eventually big suprises, as recently a larger-han-Pluto body on a very inclinated orbit.

Note that I heard figures of the maximum size for the solar system, as large as 0.1 light year, based on statistical considerations on close star encounters. We are perhaps lucky enough to have kept very far bodies and even remnants of our accretion disk, or perhaps very unlucky and an encounter was close enough to have provoked the orbit anomalies in Neptune and Pluto.

Perhaps the very inclinated object found recently was captured from another star????
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Marz
post Oct 19 2005, 03:13 PM
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In 2011, ALMA should be getting first light in Chili. One of its objectives is to "detect signatures from planets as they form and stars as they collapse and condense from an accretion of gas." So this should resolve alot of speculation about how solar systems form around different star types.

From what I've read, the planets themselves are more likely to result in ejecting each other during early solar system formation than having another star interact. Jupiter-class planets tend to act is gatekeepers; stablilizing the orbits of the other planets, and presumably correcting any perturbations from passing stars.

So therefore, maybe the Kuiper objects themselves are occassionally passing close enough to each other to act as their own nemisii (nemisises? nemisae?).
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ljk4-1
post Oct 19 2005, 04:34 PM
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QUOTE (Marz @ Oct 19 2005, 10:13 AM)
In 2011, ALMA should be getting first light in Chili.  One of its objectives is to "detect signatures from planets as they form and stars as they collapse and condense from an accretion of gas."  So this should resolve alot of speculation about how solar systems form around different star types. 

From what I've read, the planets themselves are more likely to result in ejecting each other during early solar system formation than having another star interact.  Jupiter-class planets tend to act is gatekeepers; stablilizing the orbits of the other planets, and presumably correcting any perturbations from passing stars.

So therefore, maybe the Kuiper objects themselves are occassionally passing close enough to each other to act as their own nemisii (nemisises? nemisae?).
*


Paper: astro-ph/0510527
Date: Tue, 18 Oct 2005 18:11:26 GMT (91kb)

Title: Dust Dynamics and Surface Brightness Profiles of Debris Disks: The Case
of AU Mic

Authors: Linda E. Strubbe and Eugene I. Chiang

Comments: Submitted to ApJ
\\
AU Microscopii is a 12-Myr-old M dwarf that harbors an optically thin disk of
dust. Within a projected distance b from the star of 43 AU--in the "inner
disk"--the scattered-light surface brightness falls as b^-g, where g = 1-2. In
the "outer disk," the brightness drops more steeply, with g = 4-5. We devise a
theory to explain the entire profile, including the break. Our theory asserts
that the AU Mic disk is in steady state and makes no recourse either to
unequilibrated cataclysms or to preserved primordial conditions. We posit a
ring of parent bodies on circular orbits near 43 AU: the "birth circle." At the
birth circle, grains are produced by colliding parent bodies. Grains are
removed by the star's wind and radiation, and by destructive grain-grain
collisions. Grains having sizes just large enough to remain bound to the star
occupy highly eccentric orbits and dominate scattering of starlight in the
outer disk. We prove that for large stellocentric radius r, their surface
density S scales as r^-5/2. Eccentricities and semi-major axes of all grains
decay by corpuscular and Poynting-Robertson (CPR) drag. Grains that migrate
inside the birth circle by CPR drag dominate scattering in the inner disk;
there, S scales as r^0, with modifications introduced by collisions. We predict
the outer disk to be bluer than the inner; the color gradient is sensitive to
the stellar mass-loss rate M-dot. Over the system age, the birth circle sheds
order unity of its mass, 0.6 [M-dot/(100 M-dot-sun)] lunar masses, in bodies of
size 2 [M-dot/(100 M-dot-sun)] cm. The birth circle of AU Mic resembles the
Solar System's Kuiper belt. That planetary systems have sharp outer edges
suggests planetesimal formation requires disk properties to meet threshold
conditions.

\\ ( http://arXiv.org/abs/astro-ph/0510527 , 91kb)


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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ljk4-1
post Nov 4 2005, 03:42 AM
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Paper: astro-ph/0510826

Date: Sat, 29 Oct 2005 19:20:53 GMT (773kb)

Title: The CFEPS Kuiper Belt Survey: Strategy and Pre-survey Results

Authors: R. L. Allen, B. Gladman, J-M Petit, P. Rousselot, O. Moussis, J. J.
Kavelaars, A. Campo Bagatin, G. Bernabeu, P. Benavenidez, J. Parker, P.
Nicholson, M. Holman, A. Doressoundiram, C. Veillet, H. Scholl, G. Mars

Comments: to be submitted to Icarus
\\
We present the data acquisition strategy and characterization procedures for
the Canada-France Ecliptic Plane Survey (CFEPS), a sub-component of the
Canada-France-Hawaii Telescope Legacy Survey. The survey began in early 2003
and as of summer 2005 has covered 430 square degrees of sky within a few
degrees of the ecliptic. Moving objects beyond the orbit of Uranus are detected
to a magnitude limit of $m_R$=23 -- 24 (depending on the image quality). To
track as large a sample as possible and avoid introducing followup bias, we
have developed a multi-epoch observing strategy that is spread over several
years. We present the evolution of the uncertainties in ephemeris position and
orbital elements as the objects progress through the epochs. We then present a
small 10-object sample that was tracked in this manner as part of a preliminary
survey starting a year before the main CFEPS project.

We describe the CFEPS survey simulator, to be released in 2006, which allows
theoretical models of the Kuiper Belt to be compared with the survey
discoveries since CFEPS has a well-documented pointing history with
characterized detection efficiencies as a function of magnitude and rate of
motion on the sky. Using the pre-survey objects we illustrate the usage of the
simulator in modeling the classical Kuiper Belt.

\\ ( http://arXiv.org/abs/astro-ph/0510826 , 773kb)


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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ljk4-1
post Nov 4 2005, 04:44 PM
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From: NGC 5907
Member No.: 430



QUOTE (Marz @ Oct 19 2005, 10:13 AM)
In 2011, ALMA should be getting first light in Chili.  One of its objectives is to "detect signatures from planets as they form and stars as they collapse and condense from an accretion of gas."  So this should resolve alot of speculation about how solar systems form around different star types. 

From what I've read, the planets themselves are more likely to result in ejecting each other during early solar system formation than having another star interact.  Jupiter-class planets tend to act is gatekeepers; stablilizing the orbits of the other planets, and presumably correcting any perturbations from passing stars.

So therefore, maybe the Kuiper objects themselves are occassionally passing close enough to each other to act as their own nemisii (nemisises? nemisae?).
*


http://www.nap.edu/catalog/11326.html

The Atacama Large Millimeter Array (ALMA): Implications of a Potential Descope

Committee to Review the Science Requirements for the Atacama Large Millimeter Array, National Research Council

48 pages, 6 x 9, 2005

The 1991 NRC decadal survey for astronomy and astrophysics included a project called the Millimeter Array (MMA). This instrument would be an array of millimeter-wavelength telescopes intended to capture images of star-forming regions and distant star-burst galaxies. With the addition of contributions form Europe, the MMA evolved into the Atacama Large Millimeter Array (ALMA), a proposed array of 64, 12-meter antennas. The project is now part of the NSF Major Research Equipment and Facilities budget request. Increased costs, however, have forced the NSF to reconsider the number of antennas. To help with that review, NSF asked the NRC to assess the scientific consequences of reducing the number of active antennas from 60 to either 50 or 40. This report presents an assessment of the effect of downsizing on technical performance specifications, performance degradation, and the ability to perform transformational science, and of the minimum number of antennas needed.


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Guest_Richard Trigaux_*
post Nov 5 2005, 08:37 AM
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Guests






QUOTE (ljk4-1 @ Oct 19 2005, 04:34 PM)
Paper: astro-ph/0510527
Date: Tue, 18 Oct 2005 18:11:26 GMT (91kb)

Title: Dust Dynamics and Surface Brightness Profiles of Debris Disks: The Case
of AU Mic

Authors: Linda E. Strubbe and Eugene I. Chiang

Comments: Submitted to ApJ
\\
AU Microscopii is a 12-Myr-old M dwarf that harbors ...

That planetary systems have sharp outer edges suggests planetesimal formation requires disk properties to meet threshold
conditions.

\\ ( http://arXiv.org/abs/astro-ph/0510527 , 91kb)
*


Interesting papers, ljk4-1.

I think that the disk properties required are, most obviously, its density. But the energy repartition of particules and the "exentricity and inclination" repartition may play a role in the limit. Also the presence of gas, as gas is more likely to mechanically link particules and favourize averaging of movement.

And when the criterion is met, it forms planet. But there may be intermediary cases where it forms belts of smaller bodies, like the asteroid belt and Kuyper belt.
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