November 2021 partial lunar eclipse longest for 1,000 years


The November 18-19, 2021, partial lunar eclipse will final for greater than 6 hours. The final time a partial lunar eclipse lasted that lengthy was within the 12 months 1440, when the Incas have been constructing Machu Picchu. Image through Babak Fakhamzadeh/ Unsplash. originally printed this article, which is by Graham Jones. Reprinted here with permission. Some edits by EarthSky.

Partial lunar eclipse with near-perfect alignment

The November 19, 2021, partial lunar eclipse – which is best overnight on November 18 for North America – would be the longest such occasion inside a stretch of 1,000 years. The final partial lunar eclipse that stretched longer occurred on February 18, 1440. The subsequent time Earth will see a partial lunar eclipse as prolonged as this month’s will likely be on February 8, 2669. Why is it so lengthy? As you might need guessed, the atypical actions of worlds in space play a job.

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Between 06:02 and 12:03 UTC (convert UTC to your time) on November 19, the sun, Earth, and moon will come into near-perfect alignment. Earth’s shadow will fall on the moon, ensuing within the partial lunar eclipse. At the utmost level of the eclipse – at 09:02 UTC – 99% of the moon’s face will likely be lined by the darkish inside a part of Earth’s shadow, known as the umbra. The remaining sliver of the lunar disk will likely be deep throughout the lighter, outer a part of Earth’s shadow, generally known as the penumbra.

The general period of the November 2021 eclipse – from the second the moon enters Earth’s penumbral shadow, to the second it leaves – will likely be round 21,693 seconds (about 6 hours and a couple of minutes). For a non-total lunar eclipse – in different phrases, a lunar eclipse that solely has penumbral and partial phases – that is an unusually lengthy period.

By the way in which, once we communicate of the period of this eclipse, we’re together with the penumbral phases previous and following the partial umbral eclipse. The umbral phase of the November 18-19, 2021, partial lunar eclipse is 3 hours 28 minutes and 24 seconds lengthy. It is the longest partial umbral eclipse of this century.

Viewing details on the November 18-19 eclipse here.

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Partial lunar eclipse diagram shows moon with tiny portion outside Earth's shadow.
The partial lunar eclipse of November 2021 will likely be very near a total lunar eclipse. Image through

Micromoon eclipses vs. supermoon eclipses

The November 2021 partial eclipse is longer than many total lunar eclipses. For instance, the general period of the total eclipse of May 26, 2021, was 18,127 seconds, roughly one hour much less.

Why is the November 2021 eclipse so lengthy? The most level of the eclipse comes about 41 hours earlier than the moon reaches apogee, its farthest level from Earth for this month. The farther away the moon is, the slower it travels alongside its orbit. A moon at apogee merely takes longer to go by way of Earth’s shadow.

By distinction, most eclipse in May 2021 occurred round 9 hours after perigee, the moon’s closest level to Earth for that month. Another means of claiming that is that the November eclipse includes a micromoon. Meanwhile, the May eclipse featured a supermoon.

Diagram of moon almost 100% in Earth's shadow.
In May 2021, the magnitude was barely greater than in November 2021 (it was a ‘deeper’ eclipse), however the general period was a lot shorter. Image through

Eclipses repeat in cycles

In the 1,200 years from 1451 to 2650, there are 973 partial lunar eclipses. The prime 5 eclipses by way of general period are listed under.

Longest partial lunar eclipses from 1451 to 2650

1. November 19, 2021: 21,693 seconds (6 hours 2 minutes)
2. November 30, 2039: 21,609 seconds (6 hours 0 minutes)
3. October 9, 2489: 21,557 seconds (6 hours 0 minutes)
4. December 11, 2057: 21,532 seconds (5 hours 59 minutes)
5. December 22, 2075: 21,464 seconds (5 hours 58 minutes)

Apart from the 2489 occasion, the eclipses on this record are all separated by about 18 years and 11 days. This is not any coincidence. Eclipses repeat – with very small variations – in a 6,585-day cycle generally known as the Saros.

If we return one Saros interval earlier than November 19, 2021, we arrive at November 9, 2003. The lunar eclipse that occurred on this date was virtually similar, however the total period was even longer: 21,795 seconds (6 hours 3 minutes). Why does it not present on our record above? Because the sun-Earth-moon alignment was a fraction extra good than in November 2021; the consequence was a total lunar eclipse, not a partial one.

Diagram showing moon entirely within Earth's shadow.
The interval of totality throughout the November 2003 total eclipse was a reasonably temporary 1,307 seconds (22 minutes). Image through

Bottom line: The partial lunar eclipse on November 19, 2021, would be the longest because the fifteenth century, across the time Machu Picchu was being constructed. The subsequent time Earth will see a partial lunar eclipse that lengthy will likely be on February 8, 2669. This is, coincidentally, near the 12 months that the time-travel film Bill & Ted’s Excellent Adventure begins!


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