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Mercury Science
ljk4-1
post Nov 16 2005, 02:28 PM
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Astrophysics, abstract
astro-ph/0511419

From: Stan Peale [view email]

Date: Mon, 14 Nov 2005 22:21:56 GMT (314kb)

The proximity of Mercury's spin to Cassini state 1

Authors: S. J. Peale

Comments: 23 pages,12 figures, In press in Icarus

In determining Mercury's core structure from its rotational properties, the value of the normalized moment of inertia, $C/MR^2$, from the location of Cassini 1 is crucial. If Mercury's spin axis occupies Cassini state 1, its position defines the location of the state. The spin might be displaced from the Cassini state if the spin is unable to follow the changes in the state position induced by the variations in the orbital parameters and the geometry of the solar system. The spin axis is expected to follow the Cassini state for orbit variations with time scales long compared to the 1000 year precession period of the spin about the Cassini state because the solid angle swept out by the spin axis as it precesses is an adiabatic invariant. Short period variations in the orbital elements of small amplitude should cause displacements that are commensurate with the amplitudes of the short period terms. By following simultaneously the spin position and the Cassini state position during long time scale orbital variations over past 3 million years (Quinn {\it et al.}, 1991) and short time scale variations from JPL Ephemeris DE 408 (Standish, 2005) we show that the spin axis will remain within one arcsec of the Cassini state after it is brought there by dissipative torques. We thus expect Mercury's spin to occupy Cassini state 1 well within the uncertainties for both radar and spacecraft measurements, with correspondingly tight constraints on $C/MR^2$.

http://arxiv.org/abs/astro-ph/0511419


--------------------
"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 Dec 2 2005, 05:21 PM
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Paper (*cross-listing*): gr-qc/0511137

Date: Fri, 25 Nov 2005 13:47:02 GMT (4kb)
Date (revised v2): Tue, 29 Nov 2005 11:55:15 GMT (4kb)
Date (revised v3): Thu, 1 Dec 2005 12:41:58 GMT (4kb)

Title: Can Solar System observations tell us something about the cosmological
constant?

Authors: Lorenzo Iorio

Comments: Latex2e, 4 pages, 2 table, no figures, 11 references. Table 2 added,
typos in the units of Lambda corrected
\\
In this note we show that the latest determinations of the residual Mercury's
perihelion advance, obtained by accounting for almost all known Newtonian and
post-Newtonian orbital effects, yields only very broad constraints on the
cosmological constant. Indeed, from \delta\dot\omega=-0.0036 + - 0.0050
arcseconds per century one gets -2 10^-34 km^-2 < Lambda < 4 10^-35 km^-2.

The currently accepted value for Lambda, obtained from many independent
cosmological and large-scale measurements, amounts to almost 10^-46 km^-2.

\\ ( http://arXiv.org/abs/gr-qc/0511137 , 4kb)

------------------------------------------------------------------------------

\\

Paper (*cross-listing*): gr-qc/0511138

Date: Fri, 25 Nov 2005 13:50:40 GMT (8kb)

Title: Solar System planetary motions and modified gravity

Authors: Lorenzo Iorio

Comments: Latex2e, 8 pages, 4 tables, no figures, 25 references
\\
According to the braneworld model of gravity by Dvali, Gabadadze and Porrati,
our Universe is a four-dimensional space-time brane embedded in a larger,
infinite five-dimensional bulk space. Contrary to the other forces constrained
to remain on the brane, gravity is able to explore the entire bulk getting
substantially modified at large distances. This model has not only cosmological
consequences allowing to explain the observed acceleration of the expansion of
our Universe without resorting to the concept of dark energy, but makes also
testable predictions at small scales. Interestingly, such local effects can
yield information on the global properties of the Universe and on the kind of
expansion currently ongoing. Indeed, among such predictions there are extra
precessions of the perihelia and the mean longitudes of the planetary orbits
which are affected by a twofold degeneration sign: one sign refers to a
Friedmann-Lemaitre-Robertson-Walker phase while the opposite sign is for a
self-sccelerated phase.

In this paper we report on recent observations of planetary motions in the Solar System which are compatible with the existence of a fifth dimension as predicted in the Dvali-Gabadadze-Porrati model with a self-accelerated cosmological phase, although the errors are still large. The Friedmann-Lemaitre-Robertson-Walker phase is, instead, ruled out.

\\ ( http://arXiv.org/abs/gr-qc/0511138 , 8kb)


--------------------
"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 Jan 12 2006, 08:00 PM
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Mercury a Possible Hit-and-Run Planet

http://www.space.com/scienceastronomy/0601...it_and_run.html

New computer modeling shows that the planet Mercury might have formed in a
hit-and-run collision that stripped off its outer layers.


--------------------
"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 Feb 17 2006, 08:49 PM
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Science/Astronomy:

* Catch Mercury While You Can

http://www.space.com/spacewatch/060217_night_sky.html

Once again it is time to seek out what has often been cited as the most
difficult of the five brightest naked-eye planets to see: Mercury.


--------------------
"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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odave
post Feb 18 2006, 12:26 PM
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QUOTE (ljk4-1 @ Feb 17 2006, 03:49 PM) *
...cited as the most difficult of the five brightest naked-eye planets to see


The first time I ever saw Mercury was from behind, during its 1999 transit of the sun wink.gif


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JRehling
post Feb 18 2006, 03:55 PM
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QUOTE (odave @ Feb 18 2006, 04:26 AM) *
The first time I ever saw Mercury was from behind, during its 1999 transit of the sun wink.gif


I was lucky to catch that one, too -- it was immediately before sunset at my location. But that was about the hundredth time I'd seen it.

Given its elusiveness, one of the surprising things about it is that it is one of a very few objects that can be, at certain times, the brightest object in the sky. I've seen that.

For anyone capable of programming an ephemeris-generating program, I'd like to propose the challenge of generating all the instances in the last/next X years in which Mercury is the brightest object in the sky. Off topic, but...
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Posts in this topic
- ljk4-1   Mercury Science   Nov 16 2005, 02:28 PM
- - ljk4-1   Paper (*cross-listing*): gr-qc/0511137 Date: Fri,...   Dec 2 2005, 05:21 PM
|- - ljk4-1   Mercury a Possible Hit-and-Run Planet http://www....   Jan 12 2006, 08:00 PM
|- - ljk4-1   Science/Astronomy: * Catch Mercury While You Can ...   Feb 17 2006, 08:49 PM
|- - odave   QUOTE (ljk4-1 @ Feb 17 2006, 03:49 P...   Feb 18 2006, 12:26 PM
|- - JRehling   QUOTE (odave @ Feb 18 2006, 04:26 AM) The...   Feb 18 2006, 03:55 PM
|- - Rob Pinnegar   QUOTE (JRehling @ Feb 18 2006, 08:55 AM) ...   Feb 20 2006, 06:20 AM
- - RNeuhaus   Tomorrow at 7:00 pm, the Mercury will be in half v...   Feb 19 2006, 05:01 AM
- - edstrick   Note that Mercury is actually brightest when it is...   Feb 20 2006, 06:37 AM
|- - ljk4-1   NASA Science News for February 21, 2006 Mercury m...   Feb 21 2006, 10:28 PM
- - AlexBlackwell   A paper currently in press with Icarus: Evolution...   Feb 21 2006, 10:37 PM
- - ljk4-1   MERCURY RISING - Early Mercury Impact Showered Ea...   Apr 5 2006, 02:23 PM
- - JRehling   A question that's nagged me for a long time......   Sep 28 2007, 07:07 PM
- - Greg Hullender   Have a look at chapter 2 from "The Voyage of ...   Sep 28 2007, 10:49 PM
|- - JRehling   QUOTE (Greg Hullender @ Sep 28 2007, 03:4...   Sep 28 2007, 10:57 PM
- - Mariner9   My understanding has always been that it was pure ...   Sep 29 2007, 12:19 AM
- - tasp   A couple of points: * The 2x period was desirable...   Sep 29 2007, 02:49 AM
- - tasp   {Anticipating a bad joke} Yeah, we have discussed...   Sep 29 2007, 02:54 AM
- - tasp   It is interesting, now that we are on the verge of...   Jan 31 2011, 03:36 PM
- - tasp   Maybe someone with a bit more ken of orbital mecha...   Jan 31 2011, 07:18 PM
- - Hungry4info   I don't understand why a spacecraft with an or...   Jan 31 2011, 09:33 PM
- - tasp   I was extrapolating from the 176 day orbit having ...   Jan 31 2011, 10:28 PM
- - Greg Hullender   From Kepler's laws, I figure an orbit with a p...   Feb 2 2011, 03:31 PM
|- - Littlebit   I get -1.137, so I probably have a sign error some...   Feb 2 2011, 07:07 PM
||- - ElkGroveDan   QUOTE (Littlebit @ Feb 2 2011, 11:07 AM) ...   Feb 3 2011, 05:23 AM
|- - Paolo   QUOTE (Greg Hullender @ Feb 2 2011, 04:31...   Feb 2 2011, 08:16 PM
- - tasp   As always, the folks with the math gene are very m...   Feb 2 2011, 08:26 PM
|- - Paolo   QUOTE (tasp @ Feb 2 2011, 09:26 PM) Bruce...   Feb 2 2011, 08:47 PM
- - tasp   Thanx for the correction! Ebay has a copy of ...   Feb 3 2011, 03:56 AM
- - tasp   Googling "Mariner 10 orbit" and checking...   Feb 3 2011, 05:47 AM
- - Greg Hullender   Quite easily. Mercury at Aphelion should be about ...   Feb 3 2011, 03:44 PM
- - tasp   Wow. That is getting right up there. Appreciate ...   Feb 3 2011, 04:12 PM
- - Phil Stooke   Not much action on here, but every workday there...   Jul 21 2011, 09:15 PM
- - Ant103   Wow ! It looks like a deep field with many gal...   Jul 21 2011, 09:46 PM
- - CAP-Team   Reminds me of Callisto   Jul 22 2011, 09:27 AM
- - Explorer1   First burn in orbit around Mercury (ever!) ht...   Jul 28 2011, 05:03 AM
|- - peter59   QUOTE (Explorer1 @ Jul 28 2011, 05:03 AM)...   Jul 28 2011, 06:02 AM
- - Phil Stooke   Another composite of two images from the big color...   Jul 28 2011, 03:29 PM
- - Phil Stooke   A comparison of presumably vent-like structures on...   Aug 17 2011, 03:01 PM
- - Dysgraphyk   New results on mercury shrinkage discussed in at a...   Dec 11 2013, 02:53 PM
- - Phil Stooke   http://planetarynames.wr.usgs.gov/Feature/15192 ...   Dec 16 2013, 10:04 PM
|- - tedstryk   QUOTE (Phil Stooke @ Dec 16 2013, 11:04 P...   Dec 17 2013, 09:39 PM
- - nprev   Nobody told him there'd be days like these. An...   Dec 16 2013, 10:49 PM
- - ngunn   I suppose that's appropriate. "Imagine t...   Dec 16 2013, 10:57 PM
- - MarcF   And when will they add Freddy Mercury ?? ;-) Mar...   Dec 18 2013, 04:07 PM


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