Venus transit, aureole and solar diameter

TL;DR

This paper discusses methods to measure the solar diameter using Venus transits, focusing on the aureole effect caused by Venus's atmosphere and its implications for solar measurements.

Contribution

It introduces a novel approach utilizing Venus's atmospheric refraction effects during transits to refine solar diameter measurements.

Findings

Venus's aureole provides valuable data for solar diameter estimation.

Transit observations help calibrate satellite measurements of the solar diameter.

Refraction effects are significant in interpreting transit timings.

Abstract

The possibility to measure the solar diameter using the transits of Mercury has been exploited to investigate the past three centuries of its evolution and to calibrate these measurements made with satellites. This measurement basically consists to compare the ephemerides of the internal contact timings with the observed timings. The transits of Venus of 2004 and 2012 gave the possibility to apply this method, involving a planet with atmosphere, with the refraction of solar light through it creating a luminous arc all around the disk of the planet. The observations of the 2012 transit made to measure the solar diameter participate to the project Venus Twilight Experiment to study the aureole appearing around it near the ingress/egress phases.