Proving Heliocentrism and Measuring the Astronomical Unit in a Laboratory Astronomy Class via the Aberration of Starlight

Abstract

The objective reality of the Earth's motion about the Sun was finally proven observationally by Bradley (1727) when he correctly explained the ~20'' annual, elliptical motions of stars as being due to aberration of starlight caused by the motion of the Earth. This effect can be detected today with ordinary astrophotographic equipment by measuring the coordinates of the center of star trails, which reveal the apparent position of the Celestial Poles, which vary due to the aberration of starlight, in addition to the effects of the nutation and precession of Earth's Poles. Despite my aspirations, I have not found the time to even begin the project of measuring the aberration. I nonetheless feel that it is a rich project in observational astronomy and fundamental physics, and a pleasingly didactic exercise appropriate for upper-division undergraduate and graduate astronomy and physics laboratory classes, whose complexity and length may be justified by the novelty of proving heliocentrism with nothing but a small telescope and camera. I therefore publish this Research Note to disseminate the idea in hopes that I might receive word in a few years of a triumphant astronomy class's proof of heliocentrism, along with their best estimates of the astronomical unit and precession.