Transit of Mercury

Contrary to what one might think, planets are not visible every night. It depends on the position of the Earth relative to the Sun and the planet. They are not always there, every night. If we also think about the size of the Solar System, we realize that watching one of the planets walking in front of the solar surface (as seen from Earth) is something relatively rare. This is what we call a transit of a planet. November 11 (2019) there has been the last of these transits. This time for the planet Mercury (Mercury Transit). But what is it really a transit?


A transit occurs when the Sun, the planet (in this case Mercury) and the Earth are aligned and in that order. If Mercury and Earth orbits were in the same plane, we would see Mercury pass about 3 times a year. Every time they were in conjunction. But planets do not orbit exactly on the same plane, although planes are all very close. Thus, Mercury moves in a plane that forms 7 ° with the Ecliptic (plane corresponding to the Earth), so the coincidence is much smaller: only about 13 times per century.


So every Transit of Mercury when we observe the passage of this planet in front of the Sun, is rarely seen, but it is possible. This November, the transit has been visible in its entirety from South and Central America, eastern North America, the Atlantic, the western end of Africa, including the Canary Islands (Spain).


The transit in images

In the following image and in the 4K Video of NASA the movement of Mercury is appreciated. By studying this images one can only think of two things:

  • How small we are in this Universe
  • How difficult it is to find planets around other stars …

And as a conclusion, taking into account the size of the Universe and that we have already discovered more than 4000 exoplanets so far since the first one was discovered there in 1990, we realize the huge advances made been made in astrophysics. And there is more to discover….

Transit of Mercury


The video was recorded by the NASA Solar Dynamics Observatory, which allows capturing the sun using different wavelengths of light. Source: NASA