29 research outputs found
Estimations of changes of the Sun's mass and the gravitation constant from the modern observations of planets and spacecraft
More than 635 000 positional observations (mostly radiotechnical) of planets
and spacecraft (1961-2010), have been used for estimating possible changes of
the gravitation constant, the solar mass, and semi-major axes of planets, as
well as the value of the astronomical unit, related to them. The analysis of
the observations has been performed on the basis of the EPM2010 ephemerides of
IAA RAS in post-newtonian approximation. The obtained results indicate on
decrease in the heliocentric gravitation constant per year at the level The positive secular
changes of semi-major axes have been obtained simultaneously
for the planets Mercury, Venus, Mars, Jupiter, Saturn, as expected if the
geliocentric gravitation constant is decreasing in century wise. The change of
the mass of the Sun due to the solar radiation and the solar wind and
the matter dropping on the Sun (comets, meteors, asteroids and dust) was
estimated. Taking into account the maximal limits of the possible
change, the value falls within the interval in year with the 95% probability. The
astronomical unit (au) is only connected with the geliocentric gravitation
constant by its definition. In the future, the connection between
and au should be fixed at the certain time moment, as it is inconvenient highly
to have the changing value of the astronomical unit.Comment: 20 pages, 4 tables, accepted for publication in Solar System
Research, 2011 (Astronomicheskii vestnik
Time varying gravitational constant G via the entropic force
If the uncertainty principle applies to the Verlinde entropic idea, it leads
to a new term in the Newton's second law of mechanics in the Planck's scale.
This curious velocity dependence term inspires a frictional feature of the
gravity. In this short letter we address that this new term modifies the
effective mass and the Newtonian constant as the time dependence quantities.
Thus we must have a running on the value of the effective mass on the particle
mass near the holographic screen and the . This result has a nigh
relation with the Dirac hypothesis about the large numbers hypothesis (L.N.H.)
[1]. We propose that the corrected entropic terms via Verlinde idea can be
brought as a holographic evidence for the authenticity of the Dirac idea.Comment: Accepted for publication in "Communications in Theoretical Physics
(CTP)",Major revisio
Solar System planetary tests of \dot c/c
Analytical and numerical calculations show that a putative temporal variation
of the speed of light c, with the meaning of space-time structure constant
c_ST, assumed to be linear over timescales of about one century, would induce a
secular precession of the longitude of the pericenter \varpi of a test particle
orbiting a spherically symmetric body. By comparing such a predicted effect to
the corrections \Delta\dot\varpi to the usual Newtonian/Einsteinian perihelion
precessions of the inner planets of the Solar System, recently estimated by
E.V. Pitjeva by fitting about one century of modern astronomical observations
with the standard dynamical force models of the EPM epehemerides, we obtained
\dot c/c =(0.5 +/- 2)\times 10^-7 yr^-1. Moreover, the possibility that \dot
c/c\neq 0 over the last century is ruled out at 3-12\sigma level by taking the
ratios of the perihelia for different pairs of planets. Our results are
independent of any measurement of the variations of other fundamental constants
which may be explained by a variation of itself (with the meaning of
electromagnetic constant c_EM). It will be important to repeat such tests if
and when other teams of astronomers will estimate their own corrections to the
standard Newtonian/Einsteinian planetary perihelion precessions.Comment: Latex, 12 pages, 1 figure, 3 tables, 23 references. Minor changes. To
appear in General Relativity and Gravitation (GRG
Can the Pioneer anomaly be of gravitational origin? A phenomenological answer
In order to satisfy the equivalence principle, any non-conventional mechanism
proposed to gravitationally explain the Pioneer anomaly, in the form in which
it is presently known from the so-far analyzed Pioneer 10/11 data, cannot leave
out of consideration its impact on the motion of the planets of the Solar
System as well, especially those orbiting in the regions in which the anomalous
behavior of the Pioneer probes manifested itself. In this paper we, first,
discuss the residuals of the right ascension \alpha and declination \delta of
Uranus, Neptune and Pluto obtained by processing various data sets with
different, well established dynamical theories (JPL DE, IAA EPM, VSOP). Second,
we use the latest determinations of the perihelion secular advances of some
planets in order to put on the test two gravitational mechanisms recently
proposed to accommodate the Pioneer anomaly based on two models of modified
gravity. Finally, we adopt the ranging data to Voyager 2 when it encountered
Uranus and Neptune to perform a further, independent test of the hypothesis
that a Pioneer-like acceleration can also affect the motion of the outer
planets of the Solar System. The obtained answers are negative.Comment: Latex2e, 26 pages, 6 tables, 2 figure, 47 references. It is the
merging of gr-qc/0608127, gr-qc/0608068, gr-qc/0608101 and gr-qc/0611081.
Final version to appear in Foundations of Physic
Phenomenological constraints on Lemaitre-Tolman-Bondi cosmological inhomogeneities from solar system dynamics
We, first, analytically work out the long-term, i.e. averaged over one
orbital revolution, perturbations on the orbit of a test particle moving in a
local Fermi frame induced therein by the cosmological tidal effects of the
inhomogeneous Lemaitre-Tolman-Bondi (LTB) model. The LTB solution has recently
attracted attention, among other things, as a possible explanation of the
observed cosmic acceleration without resorting to dark energy. Then, we
phenomenologically constrain both the parameters K_1 = -\ddot R/R and K_2 =
-\ddot R^'/R^' of the LTB metric in the Fermi frame by using different kinds of
solar system data. The corrections to the standard
Newtonian/Einsteinian precessions of the perihelia of the inner planets
recently estimated with the EPM ephemerides, compared to our predictions for
them, yield K_1 = (4+8) 10^-26 s^-2, K_2 = (3+7) 10^-23 s^-2. The residuals of
the Cassini-based Earth-Saturn range, compared with the numerically integrated
LTB range signature, allow to obtain K_1/2 = 10^-27 s^-2. The LTB-induced
distortions of the orbit of a typical object of the Oort cloud with respect to
the commonly accepted Newtonian picture, based on the observations of the comet
showers from that remote region of the solar system, point towards K_1/2 <=
10^-30-10^-32 s^-2. Such figures have to be compared with those inferred from
cosmological data which are of the order of K1 \approx K2 = -4 10^-36 s^-2.Comment: LaTex2e, 18 pages, 3 tables, 3 figures. Minor changes. Reference
added. Accepted by Journal of Cosmology and Astroparticle Physics (JCAP
Stochastic motion of test particle implies that G varies with time
The aim of this letter is to propose a new description to the time varying
gravitational constant problem, which naturally implements the Dirac's large
numbers hypothesis in a new proposed holographic scenario for the origin of
gravity as an entropic force. We survey the effect of the Stochastic motion of
the test particle in Verlinde's scenario for gravity\cite{Verlinde}. Firstly we
show that we must get the equipartition values for which
leads to the usual Newtonian gravitational constant. Secondly,the stochastic
(Brownian) essence of the motion of the test particle, modifies the Newton's
2'nd law. The direct result is that the Newtonian constant has been time
dependence in resemblance as \cite{Running}.Comment: Accepted in International Journal of Theoretical Physic
Effect of Sun and Planet-Bound Dark Matter on Planet and Satellite Dynamics in the Solar System
We apply our recent results on orbital dynamics around a mass-varying central
body to the phenomenon of accretion of Dark Matter-assumed not
self-annihilating-on the Sun and the major bodies of the solar system due to
its motion throughout the Milky Way halo. We inspect its consequences on the
orbits of the planets and their satellites over timescales of the order of the
age of the solar system. It turns out that a solar Dark Matter accretion rate
of \approx 10^-12 yr^-1, inferred from the upper limit \Delta M/M= 0.02-0.05 on
the Sun's Dark Matter content, assumed somehow accumulated during last 4.5 Gyr,
would have displaced the planets faraway by about 10^-2-10^1 au 4.5 Gyr ago.
Another consequence is that the semimajor axis of the Earth's orbit,
approximately equal to the Astronomical Unit, would undergo a secular increase
of 0.02-0.05 m yr^-1, in agreement with the latest observational determinations
of the Astronomical Unit secular increase of 0.07 +/- 0.02 m yr^-1 and 0.05 m
yr^-1. By assuming that the Sun will continue to accrete Dark Matter in the
next billions year at the same rate as in the past, the orbits of its planets
will shrink by about 10^-1-10^1 au (\approx 0.2-0.5 au for the Earth), with
consequences for their fate, especially of the inner planets. On the other
hand, lunar and planetary ephemerides set upper bounds on the secular variation
of the Sun's gravitational parameter GM which are one one order of magnitude
smaller than 10^-12 yr^-1. Dark Matter accretion on planets has, instead, less
relevant consequences for their satellites. Indeed, 4.5 Gyr ago their orbits
would have been just 10^-2-10^1 km wider than now. (Abridged)Comment: LaTex2e, 17 pages, no figures, 7 tables, 61 references. Small problem
with a reference fixed. To appear in Journal of Cosmology and Astroparticle
Physics (JCAP
Application of Time Transfer Function to McVittie Spacetime: Gravitational Time Delay and Secular Increase in Astronomical Unit
We attempt to calculate the gravitational time delay in a time-dependent
gravitational field, especially in McVittie spacetime, which can be considered
as the spacetime around a gravitating body such as the Sun, embedded in the
FLRW (Friedmann-Lema\^itre-Robertson-Walker) cosmological background metric. To
this end, we adopt the time transfer function method proposed by Le
Poncin-Lafitte {\it et al.} (Class. Quant. Grav. 21:4463, 2004) and Teyssandier
and Le Poncin-Lafitte (Class. Quant. Grav. 25:145020, 2008), which is
originally related to Synge's world function and enables to
circumvent the integration of the null geodesic equation. We re-examine the
global cosmological effect on light propagation in the solar system. The
round-trip time of a light ray/signal is given by the functions of not only the
spacial coordinates but also the emission time or reception time of light
ray/signal, which characterize the time-dependency of solutions. We also apply
the obtained results to the secular increase in the astronomical unit, reported
by Krasinsky and Brumberg (Celest. Mech. Dyn. Astron. 90:267, 2004), and we
show that the leading order terms of the time-dependent component due to
cosmological expansion is 9 orders of magnitude smaller than the observed value
of , i.e., ~[m/century]. Therefore, it is not possible
to explain the secular increase in the astronomical unit in terms of
cosmological expansion.Comment: 13 pages, 2 figures, accepted for publication in General Relativity
and Gravitatio
The Relativistic Factor in the Orbital Dynamics of Point Masses
There is a growing population of relativistically relevant minor bodies in
the Solar System and a growing population of massive extrasolar planets with
orbits very close to the central star where relativistic effects should have
some signature. Our purpose is to review how general relativity affects the
orbital dynamics of the planetary systems and to define a suitable relativistic
correction for Solar System orbital studies when only point masses are
considered. Using relativistic formulae for the N body problem suited for a
planetary system given in the literature we present a series of numerical
orbital integrations designed to test the relevance of the effects due to the
general theory of relativity in the case of our Solar System. Comparison
between different algorithms for accounting for the relativistic corrections
are performed. Relativistic effects generated by the Sun or by the central star
are the most relevant ones and produce evident modifications in the secular
dynamics of the inner Solar System. The Kozai mechanism, for example, is
modified due to the relativistic effects on the argument of the perihelion.
Relativistic effects generated by planets instead are of very low relevance but
detectable in numerical simulations
Phenomenology of the Lense-Thirring effect in the Solar System
Recent years have seen increasing efforts to directly measure some aspects of
the general relativistic gravitomagnetic interaction in several astronomical
scenarios in the solar system. After briefly overviewing the concept of
gravitomagnetism from a theoretical point of view, we review the performed or
proposed attempts to detect the Lense-Thirring effect affecting the orbital
motions of natural and artificial bodies in the gravitational fields of the
Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of
the impact of several sources of systematic uncertainties of dynamical origin
to realistically elucidate the present and future perspectives in directly
measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in
Astrophysics and Space Science (ApSS). Some uncited references in the text
now correctly quoted. One reference added. A footnote adde