Lorenzo Iorio

Publications (168) View all

• Source

  Available from: ArXiv

  Article: LETSGO: A spacecraft-based mission to accurately measure the solar angular momentum with frame-dragging

  L. Iorio
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  ABSTRACT: LETSGO (LEnse-Thirring Sun-Geo Orbiter) is a proposed space-based mission involving the use of a spacecraft moving along a highly eccentric heliocentric orbit perpendicular to the ecliptic. It aims to accurately measure some important physical properties of the Sun and to test some post-Newtonian features of its gravitational field by continuously monitoring the Earth-probe range. Preliminary sensitivity analyses show that, by assuming a cm-level accuracy in ranging to the spacecraft, it would be possible to test, in principle, the Lense-Thirring effect at a ∼10−2 level over a timescale of 2 years, while the larger Schwarzschild component of the solar gravitational field may be sensed with a relative accuracy of about 10−8−10−9 during the same temporal interval. The competing range perturbation due to the non-sphericity of the Sun would be a source of systematic error, but it turns out that all the three dynamical features of motion examined affect the Earth-probe range in different ways, allowing for separating them in real data analyses. The high eccentricity would help in reducing the impact of the non-gravitational perturbations whose disturb would certainly be severe when LETSGO would approach the Sun at just a few solar radii. It can be preliminarily argued that a drag-free apparatus should perform at a View the MathML source level for frequencies of about View the MathML source. Further studies should be devoted to investigate both the consequences of the non-conservative forces and the actual measurability of the effects of interest by means of extensive numerical data simulations, parameter estimations and covariance analyses. Also an alternative, fly-by configuration is worth of consideration.
  Acta Astronautica 02/2013; 86(5-6):149-157. · 0.61 Impact Factor
• Article: Local cosmological effects of the order of H in the orbital motion of a binary system

  L. Iorio
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  ABSTRACT: A two-body system hypothetically affected by an additional radial acceleration H v_r, where v_r is the radial velocity of the binary's proper orbital motion, would experience long-term temporal changes of both its semimajor axis a and the eccentricity e qualitatively different from any other standard competing effect for them. Contrary to what one might reasonably expect, the analytical expressions of such rates do not vanish in the limit M--> 0, where M is the mass of the primary, being independent of it. This is a general requirement that any potentially viable physical mechanism able to provide such a putative acceleration should meet. Nonetheless, if H had the same value H_0 of the Hubble parameter at present epoch, such rates of change would have magnitude close to the present-day level of accuracy in determining planetary orbital motions in our Solar System. A tension with recent observations may even be present for Mercury and Mars. However, general relativity, applied to a localized gravitationally bound binary system immersed in an expanding Friedmann-Lemaitre-Robertson-Walker, does not predict the existence of such a putative radial acceleration at Newtonian level. Instead, it was recently shown in literature that an acceleration of order H and directed along the velocity v of the test particle occurs at post-Newtonian level. We worked out its orbital effects finding well-behaved secular rates of change for both a and e proportional to the Schwarzschild radius r_s of the primary. Their magnitude is quite small: the rate of change of a amounts to just 20 microns per century in our Solar System. Finally, we discussed certain basic criteria of viability that modified models of gravity should generally meet when their observable effects are calculated.
  Monthly Notices of the Royal Astronomical Society 02/2013; 429(1):915-922. · 4.90 Impact Factor
• Article: A uniform treatment of the orbital effects due to a violation of the strong equivalence principle in the gravitational Stark-like limit

  L. Iorio
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  ABSTRACT: We analytically work out several effects which a violation of the Strong Equivalence Principle (SEP) induces on the orbital motion of a binary system constituted of self-gravitating bodies immersed in a constant and uniform external field. We do not restrict to the small eccentricity limit. Moreover, we do not select any specific spatial orientation of the external polarizing field. We explicitly calculate the SEP-induced mean rates of change of all the osculating Keplerian orbital elements of the binary, the perturbation of the projection of the binary orbit onto the line-of-sight, the shift of the radial velocity, and the range and range-rate signatures and as well. We find that the ratio of the SEP precessions of the node and the inclination of the binary depends only on and the pericenter of the binary itself, being independent on both the magnitude and the orientation of the polarizing field, and on the semimajor axis, the eccentricity and the node of the binary. Our results, which do not depend on any particular SEP-violating theoretical scheme, can be applied to quite general astronomical and astrophysical scenarios. They can be used to better interpret present and future SEP experiments, especially when several theoretical SEP mechanisms may be involved, and to suitably design new dedicated tests.
  Classical and Quantum Gravity 01/2013; 30(2):025006. · 3.32 Impact Factor
• Article: Solar system constraints on f(T) gravity

  L. Iorio, E. Saridakis
  Monthly Notices of the Royal Astronomical Society 11/2012; 427(2):1555–1561. · 4.90 Impact Factor
• Source

  Available from: ArXiv

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

  L. Iorio
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  ABSTRACT: The angular momentum of a star is an important astrophysical quantity related to its internal structure, formation and evolution. On average, helioseismology yields S = 1.92 10^41 kg m^2 s^-1 for the angular momentum of the Sun. We show how it should be possible to measure or, at least, constrain it in a near future by using the gravitomagnetic Lense-Thirring e?ect 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.
  Solar Physics 11/2012; 281(2):815-826. · 2.78 Impact Factor