Effect of the Solar dark matter wake on planets
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The Galaxy is conventionally thought to be surrounded by a massive dark matter (DM) halo. As the Sun goes through this halo, it excites a DM wake behind it. This local asymmetry in the DM distribution would gravitationally affect the motions of Solar System planets, potentially allowing the DM wake to be detected or ruled out. Hernandez (2019) recently calculated that the DM-induced perturbation to Saturn's position is 252 m net of the effect on the Sun. No such anomaly is seen in Saturn's motion despite very accurate tracking of the Cassini spacecraft, which orbited Saturn for >13 yr. Here, we revisit the calculation of how much Saturn would deviate from Keplerian motion if we fix its position and velocity at some particular time. The DM wake induces a nearly resonant perturbation whose amplitude grows almost linearly with time. We show that the Hernandez (2019) result applies only for an observing duration comparable to the ≈250 Myr period of the Sun's orbit around the Galaxy. Over a 100 yr period, the perturbation to Saturn's orbit amounts to <1 cm, which is quite consistent with existing observations. Even smaller perturbations are expected for the terrestrial planets.
Banik , I & Kroupa , P 2019 , ' Effect of the Solar dark matter wake on planets ' , Monthly Notices of the Royal Astronomical Society , vol. 487 , no. 4 , pp. 4565-4570 . https://doi.org/10.1093/mnras/stz1601
Monthly Notices of the Royal Astronomical Society
Copyright 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/stz1601.
DescriptionFunding Information: IB is supported by an Alexander von Humboldt postdoctoral fellowship.
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