Some Earthlings will be able to witness a total lunar eclipse on the night of Sunday to Monday, an infrequent celestial spectacle during which the nocturnal star loses its brilliance and gradually turns red.
The eclipse will be visible from parts of the American, European and African continents between moonrise and moonset.
This phenomenon occurs regarding twice a year, when the Sun, Earth and Moon are perfectly aligned, and the Moon is in its full phase.
The star slips into the shadow of the Earth, which then shields the sun’s rays, and gradually loses its white glow.
But it does not go out for all that: the Earth continues to send back to the Moon light from the Sun, via rays which take on a red hue by a process of “refraction of the atmosphere”, explains to AFP Florent Deleflie, from the Paris-PSL Observatory.
“During an eclipse, only the Earth can illuminate the Moon via this re-emission of red rays,” continues the astronomer.
“It’s very intriguing to see a bright, white Moon take on a red, extinguished hue over the minutes,” he adds. Visible with binoculars as with the naked eye, the phenomenon can give “spectacular photos” if the weather conditions are good.
The eclipse will last regarding five hours, and its totality phase – when the star is completely in the Earth’s shadow – a little over an hour.
The eclipse will be visible entirely in South America, Central America and over an eastern part of North America.
In mainland France, the eclipse will be total at the end of the night: the lunar disc will then be completely red. Note that the Moon will set during this phase of totality, at the same time as the Sun will rise.
The next total lunar eclipse is scheduled for November 2022, in the middle of the Pacific. In mainland France, the last dates back to January 2019 and the next will not take place until 2029.
Lunar eclipses have shown that the Earth was round “from antiquity”, underlines the astronomer. “On the surface of the lunar disc, the limit between the shadow and the part illuminated by the Sun is slightly curved: this is the projection of the roundness of the Earth”.
