A giant glowing X and V will appear on the Moon’s surface tonight

Two unusual formations will be visible on the Moon on Wednesday night, with a giant X and V appearing on the lunar surface.

The rare celestial event will be observable for around four hours as the Moon approaches its first quarter moon phase, with both letters forming from sunlight hitting crater’s on the Moon’s surface at just the right angle.

The lunar V appears when light illuminates the Ukert crater, while the lunar X is formed from the Bianchini, La Caille and Purbach craters.

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The lunar X and lunar V will only be observable through a telescope or binoculars pointed at the Moon’s terminator – the line separating its light and dark side.

This line is typically the most interesting part of the Moon for amateur astronomers to observe, as the shadows help to emphasize the topography.

“The lunar surface appears different nearer the terminator because there the Sun is nearer the horizon and therefore causes shadows to become increasingly long,” Nasa’s website explains.

“These shadows make it easier for us to discern structure, giving us depth cues so that the two-dimensional image, when dominated by shadows, appears almost three-dimensional.

“Therefore, as the Moon fades from light to dark, shadows not only tell us the high from the low, but become noticeable for increasingly shorter structures. For example, many craters appear near the terminator because their height makes them easier to discern there.”

The lunar X and lunar V phenomenon will appear from 4:41am on 3 July (11:41pm EDT on 2 July).

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The skies over the British Isles are expected to be mostly clear at this time, according to the latest weather forecast from the Met Office, though parts of Wales and the west coast of Ireland will be obscured by cloud.

“The Werner X does not leap out all at once but gradually appears over an interval of two hours and 20 minutes as the Sun rises on the spot,” astronomer David Chapman noted in a paper on the subject.

“Watching this is either excruciatingly slow (if you are in a hurry) or exceedingly quick (if you are attempting to sketch the scene). Remember, the Sun rises about 30 times slower on the Moon.”