Solar Oblateness Research Articles

A Theoretical Upper Bound to the Solar Oblateness

view Abstract Citations (42) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Theoretical Upper Bound to the Solar Oblateness Goldreich, Peter ; Schubert, Gerald Abstract In an earlier paper we investigated the stability of differentially rotating solar models. We concluded that in regions of constant mean molecular weight the angular momentum per unit mass could not significantly decrease away from the rotation axis (in the absence of toroidal magnetic fields). In the current investigation we show that it is conceivable for sufficiently large gradients of rotational angular velocity to exist in the Sun's core to account for the solar oblateness which Dicke and Goldenberg claim to have measured. However, we argue that it is more likely that turbulent mixing destroyed the gradients of mean molecular weight during the time when most of the Sun's angular momentum was lost and that, in reality, only very little angular momentum remains hidden in the solar interior Publication: The Astrophysical Journal Pub Date: December 1968 DOI: 10.1086/149821 Bibcode: 1968ApJ...154.1005G full text sources ADS |

Regression of the Node of the Orbit of Mercury due to a Solar Quadrupole Moment

view Abstract Citations (5) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Regression of the Node of the Orbit of Mercury due to a Solar Quadrupole Moment O'Connell, R. F. Abstract Assuming that the solar quadrupole moment is given by the value deduced by Dicke and Goldenberg from their solar oblateness measurements, Audretsch, Dehnen, and Hönl recently concluded that the node of the orbit of Mercury regresses at a rate of 3'~4 per century. However, this rate is with respect to the Sun's equatorial system. Now, the observations of all planetary orbits are described with respect to the equinox and ecliptic of a given epoch, and we show that, with respect to this system, the rate of re- gression is only O'~27 per century, which is actually smaller than the experimental error of 1" per century Publication: The Astrophysical Journal Pub Date: April 1968 DOI: 10.1086/180167 Bibcode: 1968ApJ...152L..11O full text sources ADS |

Solar rotation and the perihelion advance of Mercury

Uniformly rotating polytropic solar models are used to determine the implications of the observed solar oblateness for the perihelion advance of Mercury. In view of the hypothesized rapidly rotating solar interior, we have used the second-order theory of rotating polytropes to study rotational effects up to terms of the order ω 4, where ω is the angular velocity of rotation. It is shown that the observed oblateness necessitates a rapidly rotating core if the surface of the Sun is an equipotential surface. In terms of a simple solar model in which the radiative core and the convective envelope are dynamically distinct regions, it is shown explicitly that the core must be rotating approximately 15 times faster than the surface and also possess an oblateness of 2 × 10 −3. On the other hand, the calculations show that by regarding the core and the envelope as a single dynamical entity, it would be possible to explain the observed oblateness if the angular velocity of the Sun were only about 2.5 times the observed surface velocity. The corresponding quadrupole moment of the Sun and the corresponding perihelion advance of Mercury would be much smaller than that of the decoupled model. Other implications of having a modestly fast rotating core are also briefly discussed.

Solar Oblateness and Fluid Spin-Down

An experiment performed on a differentially rotating, density-stratified fluid shows that "spin-down" need not occur under the condition of stratification. Inasmuch as density stratification occurs in the interior of the sun, spin-down probably does not exist in the solar interior, and the observed solar oblateness may indicate that the sun contains a rapidly spinning core.

Solar Oblateness and Magnetic Field

It has been suggested that the observed Solar oblateness may be caused by a gravitational quadrupole moment. The answer may not be so simple, however, because of magnetic stress and differential rotation between the radiation layer and the core.

Solar Oblateness and the Perihelion Advances of Planets

Observations of the oblateness of the Sun suggest that it may have a rapidly spinning core. An experiment to test this suggestion, by comparing the perihelion advance of a small artificial planet of high eccentricity and Mercury, is discussed.

Differential Rotation and the Solar Oblateness

A few weeks ago, Dr I. W. Roxburgh questioned an earlier argument by Professor R. H. Dicke that the observed flattening of the Sun would account for part of the rotation of the orbit of Mercury otherwise attributable to general relativity. Roxburgh advanced arguments which suggest that the surface of the Sun may not be an equipotential surface, largely because of turbulence in the atmosphere. Dicke now rejects this interpretation.

Oblate Sun Supports Scalar-Tensor Theory

One of the three classical tests of Einstein's gravitational theory has been its prediction of Mercury's orbit; the Einstein value agreed with observations to within 1%. Now measurements by Robert H. Dicke and Mark Goldenberg of Princeton University show that the sun is slightly elliptical in shape. The quadrupole moment indicated by such a solar oblateness would perturb Mercury's motion and could account for 8% of the classical excess in the precession of Mercury's perihelion; this would imply an 8% discrepancy in the Einstein value. The other two tests of Einstein's theory are the gravitational red shift, which is also predicted by other theories, and the gravitational deflection of light, which is poorly known.

Solar Oblateness and General Relativity

Solar Oblateness and General Relativity

Rotating Solar Polytropes and the Perihelion Advance of the Planet Mercury

The contribution of rotating solar polytropes to the perihelion advance of the planet Mercury is examined as a function of observable solar oblateness.