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Independence Day revelers who turn their gaze skyward for fireworks this weekend (assuming they’re not canceled due to the coronavirus pandemic) may notice another spectacle.
Late Saturday night and early Sunday, a partial lunar eclipse will take place. Across most of North and South America, the astronomical event will start at 11:07 p.m. ET on July 4 and last until 1:52 a.m. ET on July 5.
Variable weather conditions may obscure the sky, depending on people’s locations, but the best viewing time should be around 12:30 a.m. ET.
People across western Europe and Africa may be able to glimpse the phenomenon, though it will be harder to discern as morning twilight washes over those parts of the world. Elsewhere, in Eastern Europe, Asia, and the northernmost reaches of Canada and Alaska, the event will not be visible.
What you’ll see
The nighttime effect will be a subtle one.
The moon will appear slightly darker than usual as it passes through the outer part of Earth’s shadow, called the penumbra. Even for those with good vision, the faint shading of a corner of the moon—called a partial, penumbral lunar eclipse—can be hard to see.
The visual is less dramatic than a total lunar eclipse. During this other type of eclipse, the Earth blocks all direct sunlight from reaching the moon, and light refracted through the planet’s atmosphere casts a bloody, reddish hue on its surface.
At least two lunar eclipses happen every year. This will be the third lunar eclipse of 2020 and the first one visible in the Americas since last year. The next one, also a penumbral lunar eclipse, will take place on Nov. 30.
Coincidentally, Jupiter and Saturn will also be prominently visible this weekend. Look for the two planets, which will appear as bright star-like points of light near the moon in the southeasterly sky.
When’s the next lunar eclipse?
Lunar eclipses only occur during full moons. The full moon of July is colloquially known as a Buck Moon because it appears around the time that young male deer grow their antlers.
A lunar eclipse requires the Sun, Earth, and moon to form a straight line in space. Astronomers call this celestial condition syzygy.
The next total lunar eclipse will take place next year. On May 21, 2021, the moon will completely pass through the Earth’s shadow, imparting a crimson glow that will be visible to most of the Americas, Australia, and eastern Asia.