2009/05/19 by Takaho Miura, Hideyoshi Arakida, Masumi Kasai +2 · 1 voice
Physics and Astronomy · #Cosmology and Gravitation Theories #Solar and Space Plasma Dynamics #Stellar, planetary, and galactic studies #astro-ph.EP
paper · pdf · doi:10.1093/pasj/61.6.1247
published as Publications of the Astronomical Society of Japan, Vol.61, No.6, pp.1247--1250 (2009) · 4 pages, accepted for publication in PASJ
arxiv published 2009/05/19 · arxiv created 2009/11/17 · arxiv updated 2009/11/17 · openalex publication_date 2009/12/25 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We give an idea and the order-of-magnitude estimations to explain the recently reported secular increase of the Astronomical Unit (AU) by Krasinsky and Brumberg (2004). The idea proposed is analogous to the tidal acceleration in the Earth-Moon system, which is based on the conservation of the total angular momentum and we apply this scenario to the Sun-planets system. Assuming the existence of some tidal interactions that transfer the rotational angular momentum of the Sun and using reported value of the positive secular trend in the astronomical unit, (d)/(dt)AU = 15 ± 4 (m/cy), the suggested change in the period of rotation of the Sun is about 21 ms/cy in the case that the orbits of the eight planets have the same "expansion rate." This value is sufficiently small, and at present it seems there are no observational data which exclude this possibility. Effects of the change in the Sun's moment of inertia is also investigated. It is pointed out that the change in the moment of inertia due to the radiative mass loss by the Sun may be responsible for the secular increase of AU, if the orbital "expansion" is happening only in the inner planets system. Although the existence of some tidal interactions is assumed between the Sun and planets, concrete mechanisms of the angular momentum transfer are not discussed in this paper, which remain to be done as future investigations.