In the early hours of November 19, the longest lunar eclipse of the century will be registered, during which it will look redder and more spectacular than usual, due to the recent volcanic activity registered in the volcano of La Palma, Spain, said Julieta Fierro Gossman, a researcher at the Institute of Astronomy of the UNAM.

It will be visible from 03:00 hours and will be visible until 06:30 hours; although the shadow of our planet is expected to cover 97 percent of the natural satellite's surface, it does not mean that it will disappear, but that it will show a more intense reddening, added the renowned scientific disseminator.

During eclipses, she explained, the Moon is "painted" crimson because the light from the Sun passes through the Earth's atmosphere, which works like a lens that projects it onto the planet; although the star sends out the light of all colors, the dust particles absorb blue, green and yellow light, but only red light gets through, something similar to what happens with sunsets.

The author of La astronomía de México ("Astronomy in Mexico") recalled that these natural events occur when the Earth interposes itself between the satellite and the Sun, preventing the light of our star from reaching it directly and although every year there are two eclipses during the night and two during the day, their duration varies according to the position of the Moon concerning the planet and the speed at which it moves.

Fierro Gossman pointed out: "The Moon has a slightly elliptical orbit, like the Earth. These have the characteristic that when they are closer to the main object they move faster and when they are farther away they move slower, these are the very famous Kepler's laws that tell how the planets move; and the same happens with the satellite".

The main difference this time is that the Moon is farther away from the planet, that is to say, it moves slower and therefore it is estimated that the duration will be approximately three and a half hours: the longest of the century added the winner of the Kalinga Prize.

It will be observed to a greater or lesser extent in the northern hemisphere of the Earth, so the astronomer recommended looking in the night sky, near the constellation of Orion (better known as the Three Wise Men), the Pleiades, the Moon, which will look more purple than usual due to the constant volcanism that has been recorded during 2021.

To prepare

Eclipses are important from the point of view of astronomical history, added Fierro Gossman, because you can know the shape of an object by seeing its shadow. The way the ancients knew that the Earth was round is that its shadow on the Moon is a circle, and so it was known from the time of the Babylonians that the planet had this shape.

Because for there to be eclipses the Sun, the Earth, and the Moon must be aligned, every year there are two eclipses of the Sun and two of the Moon, although the latter usually last for hours, the most difficult to appreciate are those that occur during the day, due to the intense light of the star.

In Mexico, there will be a solar eclipse in 2023 that will be appreciated in the Yucatan Peninsula, and in 2024 another one will pass from Mazatlan to Coahuila, the latter will be total and will last only four minutes.

The researcher suggested: "it will last four minutes, it is much more exciting because the sky darkens, the stars come out, the whole horizon is illuminated, as if it were a sunset, besides, it will be in April, so it will not be cloudy and the strip goes from Mazatlan to Coahuila, so it will be good to go and see it".