A deep partial eclipse of the moon occurred this morning, lasting about 3 hours 29 minutes, making it one of the longest partial eclipses ever.
One reason it lasted so long is that the moon is nearly at its farthest point in its orbit from Earth, known as the apogee. During the eclipse, the moon was about 405,344 kilometers (251,869 miles) from Earth, according to Sky Live.com. It’s still getting farther, but the actual apogee occurs only about a day and a half from the eclipse, making this one of the smallest moons we’ll ever see.
When the moon is at apogee, it’s traveling slower in its orbit than when it’s at perigee. As a result of the slower speed, the moon simply takes a longer time to pass through the Earth’s shadow, making the eclipse longer.
The 2021 Partial Lunar Eclipse at its PEAK.
97% covered by the Earth’s dark umbral shadow.
— 🔭AstroBackyard (@AstroBackyard) November 19, 2021
Another reason this partial eclipse lasted so long is that 97 percent of the moon’s disk fell in Earth’s umbral shadow, according to Earth Sky.org. In other words, there was near-perfect alignment, meaning that almost the entire moon was in the Earth’s shadow.
Longest partial lunar eclipses from 1451 to 2650:
- November 19, 2021: 21,693 seconds (6 hours 2 minutes)
- November 30, 2039: 21,609 seconds (6 hours 0 minutes)
- October 9, 2489: 21,557 seconds (6 hours 0 minutes)
- December 11, 2057: 21,532 seconds (5 hours 59 minutes)
- December 22, 2075: 21,464 seconds (5 hours 58 minutes)
The list above reflects the amount of time that elapses between the moment the moon first touches the Earth’s penumbral shadow to the moment the moon last touches Earth’s penumbral shadow. The eclipse is visible when the moon is in Earth’s umbral shadow (the Earth totally blocks light from the sun from reaching a portion of the moon’s surface).