Does the Neptunian system of satellites challenge a gravitational origin for the Pioneer anomaly?

Abstract

If the Pioneer anomaly (PA) was a genuine dynamical effect of gravitational origin, it should also affect the orbital motions of the Solar system's bodies moving in the space regions in which the PA manifested itself in its presently known form, i.e. as a constant and uniform acceleration approximately directed towards the Sun with a non‐zero magnitude after 20 au from the Sun. In this paper we preliminarily investigate its effects on the orbital motions of the Neptunian satellites Triton, Nereid and Proteus, located at about 30 au from the Sun, both analytically and numerically. Extensive observational records covering several orbital revolutions have recently been analysed for them, notably improving the knowledge of their orbits. Both analytical and numerical calculations, limited to the direct, Neptune–satellite interaction, show that the peak‐to‐peak amplitudes of the PA‐induced radial, transverse and out‐of‐plane perturbations over one century are up to 300, 600 km, 8 m for Triton, 17 500, 35 000, 800 km for Nereid and 60, 120 km, 30 m for Proteus. The corresponding orbital uncertainties obtained from a recent analysis of all the data available for the satellites considered are, in general, smaller by one–two orders of magnitude, although obtained without modelling a Pioneer‐like extra‐force. Further investigations based on a reprocessing of the satellites' real or simulated data with modified equations of motions including an additional Pioneer‐type force as well are worth being implemented and may shed further light on this important issue.

On a correlation among azimuthal velocities and the flyby anomaly sign

“…We have, for example: (a) possible anomalous advances of planetary perihelia (beyond the predictions of GR) as discussed in some studies (Iorio, 2009a; Pitjeva & Pitjev, 2013; Pitjev & Pitjeva, 2013), (b) the lingering unexplained secular increase of the eccentricity of the orbit of the Moon (Iorio, 2011a, 2011b, 2014a; Williams & Boggs, 2009; Williams, Boggs, & Folkner, 2008; Williams, Turyshev, & Boggs, 2014), (c) the so‐called “Faint Young Sun Paradox”, that is, the predictions from models of stellar evolution of a smaller energy output from the Sun in the Archean period than the one necessary to keep Earth's oceans in liquid state (Iorio, 2013; Sagan & Mullen, 1972), (d) the anomalous secular increase of the astronomical unit (Kaplan et al, 2015; Krasinsky & Brumberg, 2004; Standish, 2005), (e) a possible discrepancy between the predicted values of the Sun's angular momentum and its value constrained from planetary dynamics (Iorio, 2007a, 2012a), and (f) an anomalous Doppler blue shift for the Pioneer 10 and 11 spacecrafts corresponding to a constant acceleration a P =(8.74±1.33)×10 −8 cm s −2 , commonly known as the Pioneer anomaly (Anderson et al, 2002; Bertolami, Francisco, Gil, & Páramos, 2008, 2010; Fienga et al, 2010; Francisco, Bertolami, Gil, & Páramos, 2012; Iorio, 2007b, 2010, 2012b; Iorio & Giudice, 2006; Standish, 2008; Tangen, 2007; Turyshev & Toth, 2010; Turyshev et al, 2012).…”

Re-Examination of Globally Flat Space-Time

“…In addition, others such as [65] , [66] , and [67] have used a “Rindler-like force” emanating from the center of a gravitational source to supplement general relativistic gravity as a model that can potentially explain orbital velocity curves as well as the Pioneer anomaly [68] [69] . For a review of how this and other gravitational supplements would impact current expectations for the orbits of other major bodies in the Solar System, see [95] , [79] , [96] , [97] , [98] , [99] , [100] , [101] , [102] , [103] , [67] , [104] , [105] , [106] , [107] , [108] , and [109] . However, these supplements all require spherical symmetry about the center of the gravitational source in question and are very different from our reformulation of flat space-time where in our theory we do not assume that there exists a gravitational source at the center of galaxies, groups, clusters, etc.…”

Pioneer 10 and 11 Spacecraft Anomalous Acceleration in the light of the Nonsymmetric Kaluza–Klein (Jordan–Thiry) Theory

“…In Ref. the author raised an interesting problem to consider the Neptunian system of satellites under an influence of the Pioneer anomalous acceleration. In our approach it would be necessary to find an analogous model of acceleration for the Neptunian system as for the Solar System, which is beyond the scope of our paper (it would be necessary to add both accelerations).…”