Lorenzo Iorio

The Recently Determined Anomalous Perihelion Precession of Saturn

The astronomer E. V. Pitjeva, by analyzing with the EPM2008 ephemerides a large number of planetary observations including also two years (2004-2006) of normal points from the Cassini spacecraft, phenomenologically estimated a statistically significant nonzero correction to the usual Newtonian/Einsteinian secular precession of the longitude of the perihelion of Saturn, i.e., ; the formal, statistical error is 00007. It can be explained neither by any of the standard classical and general relativistic dynamical effects mismodeled/unmodeled in the force models of the EPM2008 ephemerides nor by several exotic modifications of gravity recently put forth to accommodate certain cosmological/astrophysical observations without resorting to dark energy/dark matter. Both independent analyses by other teams of astronomers and further processing of larger data sets from Cassini will be helpful in clarifying the nature and the true existence of the anomalous precession of the perihelion of Saturn.

Constraining the Angular Momentum of the Sun with Planetary Orbital Motions and General Relativity

The angular momentum of a star is an important astrophysical quantity related to its internal structure, formation, and evolution. Helioseismology yields

An Empirical Explanation of the Anomalous Increases in the Astronomical Unit and the Lunar Eccentricity

S_{odot}= 1.92times10^{41} mathrm{kg m^{2} s^{-1}}

Constraints on Galileon-induced precessions from solar system orbital motions

for the angular momentum of the Sun. We show how it should be possible to constrain it in a near future by using the gravitomagnetic Lense–Thirring effect predicted by General Relativity for the orbit of a test particle moving around a central rotating body. We also discuss the present-day situation in view of the latest determinations of the supplementary perihelion precession of Mercury. A fit by Fienga et al. (Celestial Mech. Dynamical Astron.111, 363, 2011) of the dynamical models of several standard forces acting on the planets of the solar system to a long data record yielded milliarcseconds per century. The modeled forces did not include the Lense–Thirring effect itself, which is expected to be as large as from helioseismology-based values of S⊙. By assuming the validity of General Relativity, from its theoretical prediction for the gravitomagnetic perihelion precession of Mercury, one can straightforwardly infer

Orbital effects of Lorentz-violating standard model extension gravitomagnetism around a static body: a sensitivity analysis

S_{odot}leq0.95times10^{41} mathrm{kg, m^{2}, s^{-1}}

Classical and relativistic long-term time variations of some observables for transiting exoplanets

. It disagrees with the currently available values from helioseismology. Possible sources for the present discrepancy are examined. Given the current level of accuracy in the Mercury ephemerides, the gravitomagnetic force of the Sun should be included in their force models. MESSENGER, in orbit around Mercury since March 2011, will collect science data until 2013, while BepiColombo, to be launched in 2015, should reach Mercury in 2022 for a year-long science phase: the analysis of their data will be important in effectively constraining S⊙ in about a decade or, perhaps, even less.

Long-term classical and general relativistic effects on the radial velocities of the stars orbiting Sgr A

The subject of this paper is the empirically determined anomalous secular increases of the astronomical unit, of the order of some cmxa0yr–1, and of the eccentricity of the lunar orbit, of the order of 10–12xa0yr–1. The aim is to find an empirical explanation of both anomalies as far as their orders of magnitude are concerned. The methods employed are working out perturbatively with the Gauss equations the secular effects on the semi-major axis a and the eccentricity e of a test particle orbiting a central body acted upon by a small anomalous radial acceleration A proportional to the radial velocity vr of the particle-body relative motion. The results show that non-vanishing secular variations and ė occur. If the magnitude of the coefficient of proportionality of the extra-acceleration is of the same order of magnitude as the Hubble parameter H 0 = 7.47 × 10–11xa0yr–1 at the present epoch, they are able to explain both astrometric anomalies without contradicting other existing observational determinations for the Moon and the other planets of the solar system. Finally, it is concluded that the extra-acceleration might be of cosmological origin, provided that the relative radial particle-body motion is accounted for in addition to that due to the cosmological expansion only. Further data analyses should confirm or disprove the existence of both astrometric anomalies as genuine physical phenomena.

Solar system constraints on a Rindler-type extra-acceleration from modified gravity at large distances

We use latest data from solar system planetary orbital motions to put con- straints on some Galileon-induced precessional effects. Due to the Vainshtein mechanism, the Galileon-type spherically symmetric field of a monopole induces a small, screened correc- tion / p r to the r −1 Newtonian potential which causes a secular precession of the pericenter of a test particle. In the case of our solar system, latest data from Mars allow to constrain the magnitude of such an interaction down to � � 0:3 level, wherecorresponds to the non minimal coupling of the Galileon to matter. Another Galileon-type effect which might impact solar system dynamics is due to an unscreened constant gradient induced by the peculiar mo- tion of the Galaxy. The magnitude of such an effect, depending on the different gravitational binding energies of the Sun and the planets, taken into account by �, is � � 0:004 from the latest bounds on the supplementary perihelion precession of Saturn.

Constraints on a MOND effect for isolated aspherical systems in the deep Newtonian regime from orbital motions

We analytically work out the long-term rates of the change of the six osculating Keplerian orbital elements of a test particle acted upon by the Lorentzviolating gravitomagnetic acceleration due to a static body, as predicted by the standard model extension. We neither restrict to any specific spatial orientation for the symmetry-violating vector s ={ −s 01 , −s 02 , −s 03 } nor make ap riorisimplifying assumptions concerning the orbital configuration of the perturbed test particle. Thus, our results are quite general, and can be applied for sensitivity analyses to a variety of specific astronomical and astrophysical scenarios. We find that, apart from the semimajor axis a, all the other orbital elements undergo non-vanishing secular variations. By comparing our results to the latest determinations of the supplementary advances of the perihelia of some planets of the solar system, we preliminarily obtain sx = (0.9 ± 1.5) × 10 −8 ,sy = (−4 ± 6) × 10 −9 andsz = (0.3 ± 1) × 10 −9 . Bounds from the terrestrial LAGEOS and LAGEOS II satellites are of the order of s ∼ 10 −3 –10 −4 .

Model-independent constraints on r-3 extra-interactions from orbital motions

We analytically work out the long-term, i.e. averaged over one orbital revolution, time varia- tions � u Yof some direct observable quantities Y induced by classical and general relativistic dynamical perturbations of the two-body point-like Newtonian acceleration in the case of transiting exoplanets moving along elliptic orbits. More specifically, the observables Y with which we deal are the transit durationtd, the radial velocity V ρ, the time intervaltecl between primary and secondary eclipses, and the time interval Ptr between successive primary transits. The dynamical effects considered are the centrifugal oblateness of both the star and the planet, their tidal bulges mutually raised on each other, a distant third-body X and general relativity (both Schwarzschild and Lense-Thirring). We take into account the effects due to the perturbations of all the Keplerian orbital elements involved in a consistent and uniform way. First, we explicitly compute their instantaneous time variations due to the dynamical effects considered and substitute them in the general expression for the instantaneous change of Y; then, we take the overall average over one orbital revolution of the so-obtained instan- taneous rate u Y (t) specialized to the perturbations considered. In contrast, previous published works have often employed somewhat hybrid expressions, in which the secular precession of, typically, the periastron only is straightforwardly inserted into instantaneous formulas. The transit duration is affected neither by the general relativistic Schwarzschild-type nor by the classical tidal effects, while the bodies centrifugal oblatenesses, a distant third-body X and the general relativistic Lense-Thirring-type perturbations induce non-vanishing long-term, harmonic effects ontd also for circular orbits. For exact edge-on configurations they vanish. Both V ρ andtecl experience non-vanishing long-term, harmonic variations, caused by all the perturbations considered, only for non-circular orbits. Also Ptr is affected by all of them with long-term signatures, but they do not vanish for circular orbits. Numerical evaluations of the obtained results are given for a typical star-planet scenario and compared with the expected observational accuracies over a time-span τ = 10 yr long. Also graphical investigations of the dependence of the effects considered on the semimajor axis and the eccentricity are presented. Our results are, in principle, valid also for other astronomical scenarios. They may allow, e.g., for designing various tests of gravitational theories with natural and artificial bodies in our Solar system.