[X] My Assistant

[ljk4-1]

Paper: astro-ph/0601369
Date: Tue, 17 Jan 2006 15:03:37 GMT (196kb)

Title: The Titius-Bode law of planetary distances: new approach

Authors: V. M. Bakulev

Comments: 14 pages including 3 tables and 3 figures
\\
The new approach of the regular spacing of planetary orbits and planet mass
distribution in the Solar system is considered. The relative planetary
distances will be represented as the inverse composite probabilities of two
discrete distributions with one fitted parameter. Conceivable physical
interpretation of these distributions and fitted parameter will be suggested.

The parameters of the orbits of the newly discovered transneptunian objects are
compared with predicted planetary orbits.

\\ ( http://arXiv.org/abs/astro-ph/0601369 , 196kb)

[nprev]

Hmm...Forgot all about Titus-Bode. Do the multiple planet systems around 47 Ursa Majoris, 55 Cancri and/or Upsilon Andromedae adhere even approximately to this?

I can't recall if the planets in any of these systems have relatively circular orbits like ours, though, so a 1:1 comparison might not be possible.

[ljk4-1]

Paper: astro-ph/0601612

Date: Thu, 26 Jan 2006 18:39:51 GMT (13kb)

Title: Two-body problem with the cosmological constant and observational
constraints

Authors: Ph. Jetzer (Uni. Zurich) M. Sereno (Uni. Zurich)

Comments: 8 pages, accepted for publication in Phys. Rev. D
\\
We discuss the influence of the cosmological constant on the gravitational
equations of motion of bodies with arbitrary masses and eventually solve the
two-body problem. Observational constraints are derived from measurements of
the periastron advance in stellar systems, in particular binary pulsars and the
solar system. Up to now, Earth and Mars data give the best constraint, Lambda <
10^{-36} km^{-2}; bounds from binary pulsars are potentially competitive with
limits from interplanetary measurements. If properly accounting for the
gravito-magnetic effect, this upper limit on $\Lambda$ could greatly improve in
the near future thanks to new data from planned or already operating
space-missions.

\\ ( http://arXiv.org/abs/astro-ph/0601612 , 13kb)

[Guest_BruceMoomaw_*]

The disorderliness of other planetary systems has pretty much put paid to the idea of Titius-Bode except as an interesting coincidence.

[The Messenger]

The disorderliness of other planetary systems has pretty much put paid to the idea of Titius-Bode except as an interesting coincidence.

It doesn't seem to apply to the sub-planet sytems of Saturn and Jupiter, and since the distant systems we have encountered bracket the high end, it is hard to cling to Bode's law.

[David]

It doesn't seem to apply to the sub-planet sytems of Saturn and Jupiter, and since the distant systems we have encountered bracket the high end, it is hard to cling to Bode's law.

Maybe not as a rigorous formula for placing orbits, but the Jovian and Saturnian systems are like the Solar System in a more general sense: having orbits in or near the equatorial plane more tightly packed closer to the primary, more widely spaced farther away, with non-planar orbits in a random looking cloud at an even farther distance; also that the inner disk satellites tend to be smaller and the outer ones larger (with the largest satellites -- Ganymede, Titan, Titania -- not being the outermost large ones). I assume this relates to some common process of formation of satellites from orbiting disks of material, but I have no idea if it's amenable to a mathematical formula. Has anyone ever tried analyzing the spacing of the Jovian and Saturnian moons?

[dilo]

Has anyone ever tried analyzing the spacing of the Jovian and Saturnian moons?

I remeber an old article showing similar laws also for these systems! I have to search...

[Bob Shaw]

I remeber an old article showing similar laws also for these systems! I have to search...

Try looking for Asimov and Dole's 'Habitable Planets for Man' - they set up a variety of Titius-Bode scenarios, though they did so thirty years before any extra-Solar planets were found so it was *pure* speculation.

Bob Shaw

[edstrick]

Note that "Habitable Planets for Man" exists in two versions, I don't recall how the titles differ. One is full of technical details, the other is a "readers digest" version, simplified for the general reader.

[The Messenger]

I remeber an old article showing similar laws also for these systems! I have to search...

If they do, I withdraw my dismissal. One thing that should be looked at, is if the 'rough integer' spacing could be better expressed as a natural logrythm relative to the moment of inertia of a central body.

[ljk4-1]

Here is the original 1964 RAND book by Stephen Dole, Habitable Planets for Man, online free in PDF format:

http://www.rand.org/pubs/reports/R414/


This fellow has created an online software program that generates various solar systems both real and imagined, based on his initial encounter with Planets for Man:

http://home.comcast.net/~brons/NerdCorner/...en/StarGen.html


Another world building program, based on ACCRETE:

http://www.znark.com/create/


Other references:

http://www.sfsite.com/fsf/2002/cur0203.htm

http://adsabs.harvard.edu/cgi-bin/nph-bib_...TML&format=

http://adsabs.harvard.edu/cgi-bin/nph-bib_...TML&format=

[ljk4-1]

Astrophysics, abstract
astro-ph/0602086

From: George Kaplan [view email]

Date: Fri, 3 Feb 2006 20:43:57 GMT (297kb)

The IAU Resolutions on Astronomical Reference Systems, Time Scales, and Earth Rotation Models

Authors: George H. Kaplan (U.S. Naval Observatory)

Comments: 118 pages, 6 figures. Includes 6 main chapters plus table of contents, introductory material, references, and appendices. Available in hardback print edition and as a high-quality PDF file; see this http URL

Report-no: Circ. 179

Journal-ref: Kaplan, G. H., 2005, U.S. Naval Observatory Circular No. 179 (Washington: USNO)

Recent resolutions passed by the International Astronomical Union (IAU) on astronomical reference systems, time scales, and Earth rotation models are the most significant set of international agreements in positional astronomy in several decades. These resolutions, the result of over ten years of international research and study, provide a coherent set of foundational standards for the treatment of astrometric data and the modeling of dynamics in the solar system. This circular explains these resolutions and provides a complete set of practical formulas for their implementation. The six main chapters cover relativity, time scales, the fundamental celestial reference system, ephemerides of solar system bodies, precession and nutation, and modeling the Earth's rotation.

http://arxiv.org/abs/astro-ph/0602086

[Bob Shaw]

Note that "Habitable Planets for Man" exists in two versions, I don't recall how the titles differ.  One is full of technical details, the other is a "readers digest" version, simplified for the general reader.

The RAND report is indeed the real, single-author thing; the colouring-in version must have been co-written with Asimov.

Well worth a download - lots of other goodies at RAND, too!

Bob Shaw

[tasp]

Before the observations were discredited, the 3 planets detected at Barnard's Star were pretty close to the expected Bode spacings.

IIRC, the observations were traced to periodic adjustments to the telescope (Sproul Observatory??) and not to planets at Barnard's Star.

{I realize this isn't terribly relevant to the topic, but for many, many years, those possible planets were it for those of us bored to death (imagine that!) with our dull pre-Voyager solar system.}

[The Messenger]

Before the observations were discredited, the 3 planets detected at Barnard's Star were pretty close to the expected Bode spacings.

IIRC, the observations were traced to periodic adjustments to the telescope (Sproul Observatory??) and not to planets at Barnard's Star.

{I realize this isn't terribly relevant to the topic, but for many, many years, those possible planets were it for those of us bored to death (imagine that!) with our dull pre-Voyager solar system.}

Actually it is, because if the 'periodic adjustments', were a 'pretty close fit', 'pretty close' would seem to have enough latitude to drive a truck through.

[ljk4-1]

Astrophysics, abstract
astro-ph/0602217

From: Dimitar Sasselov [view email]

Date: Thu, 9 Feb 2006 21:42:02 GMT (35kb)

On the Location of the Snow Line in a Protoplanetary Disk

Authors: M. Lecar (1), M. Podolak (2), D. Sasselov (1), E. Chiang (3) ((1)Harvard-Smithsonian CfA, (2)Tel Aviv Univ., (3)UC Berkeley)

Comments: Accepted for publication in ApJ, 9 pages, 4 figures

In a protoplanetary disk, the inner edge of the region where the temperature falls below the condensation temperature of water is referred to as the 'snow line'. Outside the snow line, water ice increases the surface density of solids by a factor of 4. The mass of the fastest growing planetesimal (the 'isolation mass') scales as the surface density to the 3/2 power. It is thought that ice-enhanced surface densities are required to make the cores of the gas giants (Jupiter and Saturn) before the disk gas dissipates. Observations of the Solar System's asteroid belt suggest that the snow line occurred near 2.7 AU. In this paper we revisit the theoretical determination of the snow line. In a minimum-mass disk characterized by conventional opacities and a mass accretion rate of 10^-8 solar masses per year, the snow line lies at 1.6-1.8 AU, just past the orbit of Mars. The minimum-mass disk, with a mass of 0.02 solar, has a life time of 2 million years with the assumed accretion rate. Moving the snow line past 2.7 AU requires that we increase the disk opacity, accretion rate, and/or disk mass by factors ranging up to an order of magnitude above our assumed baseline values.

http://arxiv.org/abs/astro-ph/0602217

[ljk4-1]

Astrophysics, abstract
astro-ph/0602438

From: Mauro Sereno [view email]

Date: Mon, 20 Feb 2006 19:11:18 GMT (10kb)

Solar and stellar system tests of the cosmological constant

Authors: M. Sereno (Univ. Zurich), Ph. Jetzer (Univ. Zurich)

Comments: 4 pages; this is a preprint of an article accepted for publication in Physical Review D

Some tests of gravity theories - periastron shift, geodetic precession, change in mean motion and gravitational redshift - are applied in solar and stellar systems to constrain the cosmological constant. We thus consider a length scale range from 10^8 to 10^{15} km. Best bounds from the solar system come from perihelion advance and change in mean motion of Earth and Mars, Lambda < 10^{-36} km^{-2}. Such a limit falls very short to estimates from observational cosmology analyses but a future experiment performing radio ranging observations of outer planets could improve it by four orders of magnitude. Beyond the solar system, together with future measurements of periastron advance in wide binary pulsars, gravitational redshift of white dwarfs can provide bounds competitive with Mars data.

http://arxiv.org/abs/astro-ph/0602438

[ljk4-1]

EXO WORLDS

- Simulation Tracks Planetary Evolution

http://www.spacedaily.com/reports/Simulati..._Evolution.html

London, UK (SPX) Mar 21, 2006 - Two British astronomers have constructed a
computer simulation that tracks how giant protoplanets tend to form and migrate
inward toward their central star.