Transits of Venus and the Astronomical Unit: four centuries of increasing precision

TL;DR

This paper reviews four centuries of observations of Venus transits, highlighting their importance in measuring the Astronomical Unit, studying planetary atmospheres, and understanding observational phenomena like the black drop.

Contribution

It provides a comprehensive historical overview of Venus transits and their role in refining astronomical measurements over four centuries.

Findings

Improved precision in measuring the Astronomical Unit

Insights into Venus's atmosphere and properties

Understanding of the black drop phenomenon

Abstract

Only seven transits of Venus have been observed and studied up to now since the first astronomical observations with the telescope: 1639, 1761-69, 1874-82 and 2004-12. The measurement of the Astronomical Unit has been one of the main goal of the study of this rare phenomenon, as well as the identification of the planetary atmosphere and its properties, the understanding of the black drop phenomenon and the measurement of the solar diameter. The transit of 1639 observed by J. Horrocks is presented in more detail.