Anomalous Sun Flyby of 1I/2017 U1 (`Oumuamua)

The findings of Micheli et al. (Nature2018, 559, 223–226) that 1I/2017 U1 (`Oumuamua) showed anomalous orbital accelerations have motivated us to apply an impact model of gravity in search for an explanation. A small deviation from the 1/r potential, where r is the heliocentric distance, is expected for the gravitational interaction of extended bodies as a consequence of this model. This modification of the potential results from an offset of the effective gravitational centre from the geometric centre of a spherically symmetric body. Applied to anomalous Earth flybys, the model accounts for energy gains relative to an exact Kepler orbit and an increased speed of several spacecraft. In addition, the flat rotation profiles of eight disk galaxies could be explained, as well as the anomalous perihelion advances of the inner planets and the asteroid Icarus. The solution in the case of `Oumuamua is also based on the proposal that the offset leads to an approach and flyby trajectory different from a Kepler orbit without postulating cometary activity. As a consequence, an adjustment of the potential and centrifugal orbital energies can be envisaged outside the narrow uncertainty ranges of the published post-perihelion data without a need to re-analyse the original data. The observed anomalous acceleration has been modelled with respect to the orbit solutions JPL 16 and “Pseudo-MPEC” for 1I/`Oumuamua.

Remark on ``Indication, from Pioneer 10/11, Galileo, and Ulysses Data, of an Apparent Anomalous, Weak, Long-Range Acceleration''

Recently, Anderson et al. presented possible evidence for an anomalous acceleration acting on spacecrafts. Furthermore, the motions of several planets and comets are known to experience unexplained disturbances. A transneptunian comet or asteroid belt might be the common origin of these anomalies.

Anomalous acceleration of mass loss in the Greenland ice sheet drainage basins and its contribution to the sea level fingerprints during 2010–2012

The sea level rise contributed from ice sheet melting has been accelerating due to global warming. Continuous melting of the Greenland ice sheet (GrIS) is a major contributor to sea level rise, which impacts directly on the surface mass balance and the instantaneous elastic response of the solid Earth. To study the sea level fingerprints (SLF) caused by the anomalous acceleration of the mass loss in GrIS can help us to understand drivers of sea level changes due to global warming and the frequently abnormal climate events. In this study, we focus on the anomalous acceleration of the mass loss in GrIS at the drainage basins from 2010 to 2012 and on its contributions to SLF and relative sea level (RSL) changes based on self-attraction and loading effects. Using GRACE monthly gravity fields and surface mass balance (SMB) data spanning 13 years between 2003 and 2015, the spatial and temporal distribution of the ice sheet balance in Greenland is estimated by mascons fitting based on six extended drainage basins and matrix scaling factors. Then the SLF spatial variations are computed by solving the sea level equation. Our results indicate that the total ice sheet mass loss is contributed from few regions only in Greenland, i.e., from the northwest, central west, southwestern and southeastern parts. Especially along the north-west coast and the south-east coast, ice was melting significantly during 2010–2012. The total mass loss rates during 2003–2015 are −288±7 Gt/yr and −275±1 Gt/yr as derived from scaled GRACE data and SMB respectively; and the magnitude of the trend increased to −456±30 Gt/yr and to −464±38 Gt/yr correspondingly over the period 2010–2012. The residuals obtained by GRACE after removing SMB show a good agreement with the surface elevation change rates derived from pervious ICESat results, which reflect a contribution from glacial dynamics to the total ice mass changes. Melting of GrIS results in decreased RSL in Scandinavia and North Europe, up to about −0.6 cm/yr. The far-field peak increase is less dependent on the precise pattern of self-attraction and loading; and the average global RSL was raised by 0.07 cm/yr only. Greenland contributes about 31 % of the total terrestrial water storage transferring to the sea level rise from 2003 to 2015. We also found that variations of the GrIS contribution to sea level have an opposite V shape (i.e., from rising to falling) during 2010–2012, while a clear global mean sea level drop also took place (i.e., from falling to rising).

A Statistical Study of Unusual Tracks of Tropical Cyclones near Taiwan Island

Tropical cyclones (TCs) tend to change translation direction and speed when moving across Taiwan’s Central Mountain Range (CMR), which makes forecasting of landfalling points a challenging task. This study examines the statistical characteristics of unusual TC tracks around Taiwan Island during the 66-yr period of 1949–2014. Results show that 1) about 10% more TCs were deflected to the right than to the left as they moved across the CMR, but with more occurrences of the latter on Taiwan’s eastern coast and southern strait; 2) TCs around Taiwan Island moved slower than the average speed over the western North Pacific Ocean but then exhibited anomalous acceleration along Taiwan’s eastern coast and anomalous deceleration over the southern Taiwan Strait; 3) about 33% of TCs passing the island were accompanied by terrain-induced secondary low pressure centers (SCs), more favored in the northwestern, southwestern, and southeastern quadrants, with the TC–SC separation distance varying from 33 to 643 km; 4) about 36% of landfalling TCs experienced discontinuous tracks, with an average separation distance of 141 km at the time when TC centers were replaced by SCs, and smaller Froude numbers than those associated with continuous-tracking TCs; and 5) a total of 12 TCs had looping movements near Taiwan Island, most of which were accompanied by SCs on their southern or western sides. Results also indicate that a stronger SC was likely to take place when a stronger TC approached the CMR with a shorter separation distance and that a weaker SC was likely to take place when a weaker TC approached the CMR with a longer separation distance.

An instability of the standard model of cosmology creates the anomalous acceleration without dark energy

We identify the condition for smoothness at the centre of spherically symmetric solutions of Einstein’s original equations without the cosmological constant or dark energy. We use this to derive a universal phase portrait which describes general, smooth, spherically symmetric solutions near the centre of symmetry when the pressure p =0. In this phase portrait, the critical k =0 Friedmann space–time appears as a saddle rest point which is unstable to spherical perturbations. This raises the question as to whether the Friedmann space–time is observable by redshift versus luminosity measurements looking outwards from any point. The unstable manifold of the saddle rest point corresponding to Friedmann describes the evolution of local uniformly expanding space–times whose accelerations closely mimic the effects of dark energy. A unique simple wave perturbation from the radiation epoch is shown to trigger the instability, match the accelerations of dark energy up to second order and distinguish the theory from dark energy at third order. In this sense, anomalous accelerations are not only consistent with Einstein’s original theory of general relativity, but are a prediction of it without the cosmological constant or dark energy.