A measurement of the shape of the solar disk: The solar quadrupole moment, the solar octopole moment, and the advance of perihelion of the planet Mercury

The Solar Disk Sextant experiment has measured the solar angular diameter for a variety of solar latitudes. Combined with solar surface angular rotation data, the solar quadrupole moment J(2) and the solar octopole moment J(4) have been derived first by assuming constant internal angular rotation on cylinders and then by assuming constant internal angular rotation on cones. We have derived values of 1.8 x 10(-7) for J(2) and 9.8 x 10(-7) for J(4). We conclude with a discussion of errors and address the prediction of general relativity for the rate of advance of perihelion of the planet Mercury.