Astonishing image: Mercury passes between the Earth and the Sun

Mercury moves through the Sun on Monday (November 11), also known as "Mercury in transit". This is a relatively rare astronomical event, and will not happen until 2032.

Mercury is the smallest planet in the solar system, with a diameter of 3,000 miles compared to the Sun 864,000 miles. This is Mercury's first transit of the Sun since 2016. Unlike the 2016 transit, this time Mercury is closest to Earth, passing right in front of our planet. This year, Mercury will take about 5.5 hours to complete the journey, cross the halfway road at 22h20 and finish transit in 1am on 12/11. According to NASA, during a century Mercury only transited 13 or 14 times.

The image of Mercury (the black dot in the circle) passing by the Sun was recorded by NASA on 11/11/2019.

During transit, Mercury passes between the Sun and the Earth, becoming a small black dot in contrast to the bright yellow disk of the Sun. Therefore, to protect the eyes, astronomers believe that this phenomenon should not be observed with the naked eye, looking directly at the sun can be harmful to the eyes. Seen from Earth, Mercury's black dot is about 1/160 the width of the Sun, so observers need observation aids like ultraviolet filters to track transit events.

Observing movements like this have played an important role in the history of astronomy development, especially in answering a simple but important question - exactly how far the Earth is from the Sun. ? Without this number, we cannot know the distances of planets from the Sun, even the actual brightness of the Sun.

Renowned astronomer Edmond Halley (the name given to Halley's comet) realized that observations of the interplanetary shifts of the planets - particularly Venus passing through the Sun disk - could be used. to answer this.

The measurement is an example of parallax: the apparent position of a nearby object, relative to a distant background, depends on your vantage point. The closer the object is, the bigger the parallax: Halley reasoned that by measuring Venus' position relative to the farther Sun, it was possible to calculate the distance to the Sun. At least in theory.

1. Mercury passes through the Sun - a rare astronomical phenomenon is about to take place