Sunday, 24 March 2024

Penumbral lunar eclipse to be visible from the Americas, Western Europe, West Africa, Eastern Australia, New Guinea, Oceana, Japan, the Russian Far East, and the Pacific and Atlantic Oceans.

A penumbral Lunar Eclipse will occur on Monday 25 March 2024, starting at 4.53 am GMT and ending at 9.32 am GMT. The whole eclipse will be visible across all of the Americas except eastern Brazil, while part of the eclipse will be visible from the remainder of Brazil, Western Europe, West Africa, Eastern Australia, New Guinea, Oceana, Japan, the Russian Far East, and the Pacific and Atlantic Oceans, although in these areas the Moon will either rise part way through the eclipse, or set before it is complete.

Map showing areas from which the 25 March 2023 penumbral lunar eclipse will be visible. Time and Date.

The Moon produces no light of its own, but 'shines' with reflected light from the Sun. Thus, at Full Moon the Moon is on the opposite side of the Earth to the Sun, and its illuminated side is turned towards us, but at New Moon the Moon is between the Earth and the Sun, so that its illuminated side is turned away from us.

Lunar eclipses occur when the Moon passes through the Earth's shadow. This can only happen at Full Moon (unlike Solar Eclipses, which happen only when the Moon passes between the Earth and the Sum, and therefore only occur at New Moon), but does not happen every Lunar Month as the Sun, Moon and Earth are not in a perfect, unwavering line, but rather both the Earth and the Moon wobble slightly as they orbit their parent bodies, rising above and sinking bellow the plane of the ecliptic (the plane upon which they would all be in line every month).

Because the Moon is passing through a shadow, rather than being blocked from our view, it does not completely disappear during an eclipse like the Sun, but in a total Lunar Eclipse goes through two distinct phases of dimming, the Penumbra, when it is still partially illuminated by the Sun, and the Umbra, when the Earth completely blocks direct sunlight from the Moon. This does not result in complete darkness, as the Moon is still partially lit by reflected Earthlight, but it does turn a deep, dark red colour.  In a penumbral eclipse only the first of these phases occurs.

(Top) The geometry of the Earth's shadow. Within the Earth's penumbral shadow, the planet covers some fraction the Sun's disk. Only within the smaller umbra does the Earth cover the entirety of the Sun's disk. Any areas of the Moon's surface that pass through the penumbra appear darker than usual as the Earth is obstructing some of the sunlight that usually illuminates them. Areas within the umbra, meanwhile, receive no illumination from the Sun at all. Time and Date. (Bottom) The passage of the Moon through the Earth's penumbral shadow during the 25 March 2024 penumbral lunar eclipse. Guy Ottewell/EarthSky.

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