Longest partial lunar eclipse of the century is happening on Friday

A deep partial lunar eclipse will occur on Friday, November 19, 2021 and will be visible to stargazers from most of the locations on the globe. This will be the longest partial lunar eclipse of the century, lasting 3.5 hours – an unusually long time for partial eclipses.

“When you have a total lunar eclipse, it’s not uncommon to have the entirety of that lasting for three-and-a-half hours, sometimes a bit shorter, sometimes longer. But for a partial eclipse to last this long, it’s just very rare,” said Rob Davidson, an astronomer at Auckland’s Stardom Observatory. 

“Most of the eclipse will be dominated by the shadow moving across the moon, with a brief period where it will appear as a blood micromoon in our night sky.”

According to Davidson, this is a rare event not only because it is such a long partial lunar eclipse, but also due to the position of the moon in its orbit.

“The moon is at apogee, which means it’s at the farthest point from Earth in its orbit. The moon’s orbit around the Earth is not a perfect circle, it’s an ellipse which means as it goes around, it comes a little bit closer and then, as it swings around, it goes a little bit further away,” he explained.

“So when it’s at its closest point, it’s called perigee, and that’s when you get a so-called super moon – about 360,000 kilometres away. When it swings around to the other side, and is in apogee, it’s about 400,000 kilometres away.” 

The reason this will be such a long eclipse – the longest one since 1440 – is that the moon moves slower during its apogee.

While this eclipse will be perfectly visible from locations such as North America, New Zealand, Asia, and Australia, from South America and Western Europe the later stages of the eclipse will not be visible since moonset will occur before the eclipse ends. 

According to the Royal Observatory, Greenwich, the partial eclipse will be “barely visible in the UK” since it occurs when the moon is close to or below the horizon, and, sadly, it will not be visible at all from Africa or the Middle East. 

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By Andrei Ionescu, Earth.com Staff Writer