9 research outputs found
Effect of inhomogeneity of the Universe on a gravitationally bound local system: A no-go result for explaining the secular increase in the astronomical unit
We will investigate the influence of the inhomogeneity of the universe,
especially that of the Lema{\^i}tre-Tolman-Bondi (LTB) model, on a
gravitationally bound local system such as the solar system. We concentrate on
the dynamical perturbation to the planetary motion and derive the leading order
effect generated from the LTB model. It will be shown that there appear not
only a well-known cosmological effect arisen from the homogeneous and isotropic
model, such as the Robertson-Walker (RW) model, but also the additional terms
due to the radial inhomogeneity of the LTB model. We will also apply the
obtained results to the problem of secular increase in the astronomical unit,
reported by Krasinsky and Brumberg (2004), and imply that the inhomogeneity of
the universe cannot have a significant effect for explaining the observed
.Comment: 12 pages, no figure, accepted for publication in Journal of
Astrophysics and Astronom
Intrinsic Shapes of Elliptical Galaxies
Tests for the intrinsic shape of the luminosity distribution in elliptical
galaxies are discussed, with an emphasis on the uncertainties. Recent
determinations of the ellipticity frequency function imply a paucity of nearly
spherical galaxies, and may be inconsistent with the oblate hypothesis.
Statistical tests based on the correlation of surface brightness, isophotal
twisting, and minor axis rotation with ellipticity have so far not provided
strong evidence in favor of the nearly oblate or nearly prolate hypothesis, but
are at least qualitatively consistent with triaxiality. The possibility that
the observed deviations of elliptical galaxy isophotes form ellipses are due to
projection effects is evaluated. Dynamical instabilities may explain the
absence of elliptical galaxies flatter than about E6, and my also play a role
in the lack of nearly-spherical galaxies