When a star passes in front of a larger one, the phenomenon known as transit occurs. The most common is the solar eclipse , in which the Moon "covers" the Sun for a while.
The most unusual transits are planetary transits , which occur when a planet is placed on the disk of the Sun. This phenomenon can only be observed from Earth when the inner planets are aligned in this way, that is, when Mercury or Venus align between the Sun and the Earth.
The transit of Mercury is the most common. Astronomers estimate that it occurs about 13 times over a century . The first to be observed was in 1631, visualized by the French astronomer Gassendi.
Venus is less common . It happens twice with 8 years between one and the other, and then an interval of between 105 and 121 years passes until it happens again. The first known transit of Venus was a month after Mercury, but this time Gassendi could not observe it because it was not visible from Europe. The transit of Mercury occurs between November 8 and 10, and in the case of Venus in early December or June.
