Use of Transits of Venus

A transit of Venus occurs when Venus passes directly between the Earth and the Sun, appearing as a small black disc against the Sun’s bright disc.
This phenomenon is relatively rare, with pairs of transits occurring eight years apart, but each pair separated by over a century.

Transits of Venus have been valuable in astronomy because they have helped scientists determine the absolute dimensions of the solar system.
The use of transits of Venus helped to establish the Astronomical Unit (AU), the average distance from Earth to the Sun.

Using geometry and observations of transits of Venus from different locations on Earth, astronomers were able to calculate the AU.
The method involves observing the transit from two distant locations on Earth, and measuring the time difference between when Venus first appears to touch the Sun’s disc at each location.
This time difference and the known distance between the two locations enable astronomers to calculate the distance to Venus during the transit, and thus the scale of the solar system.

Although we now have other ways to measure distances in the solar system, transits of Venus are still of interest to scientists.
Modern observations of transits are used to study the atmosphere of Venus, by analysing the light that shines through it from the Sun.
These techniques are also used to detect and study exoplanets, planets outside our solar system. Observing transits of exoplanets can reveal information about their size, orbit, and atmosphere.