For 14 minutes and 30 seconds on May 26, 2021, the only light that reaches the Moon’s surface will have first been filtered by Earth’s atmosphere.
For some scientists, that proved a lightbulb moment last time out.
The coming full “Flower Moon”—despite also being the year’s biggest “supermoon”—will dim considerably and turn a kind of copper color.
Visible to those on the Pacific Rim—including western U.S. states—it’s a fleeting sight that hasn’t happened since the “Super Wolf Blood Moon” of January 20, 2019.
Although it’s thought of only as a visual treat for moongazers, some significant science was achieved during that last total lunar eclipse.
Here’s what was discovered during the Moon’s last trip through Earth’s shadow in space.
1. Total lunar eclipse: a meteorite strikes the lunar surface
The Moon is covered in craters. Obviously. So it figures that just occasionally it will be possible to see a bright flash as a meteorite strikes the lunar surface. That’s exactly what happened on January 20, 2019 when photographers and videographers captured a 0.28 seconds-long flash on the edge of the Moon as totality was turning our satellite a deep reddish-orange.
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It was something that Jose Maria Madiedo at Spain’s University of Huelva had hoped to observe, and with colleagues they set-up eight telescopes specially to collect data at different wavelengths.
They got it—and published a paper about their success, the first time ever that an impact flash was unambiguously recorded during a lunar eclipse.
What’s more, they revealed that a similar event was recorded during the total lunar eclipse of January 21, 2000. Since near-identical lunar eclipses occur almost exactly every 19 years, some have speculated that both impacts were caused by the same minor Sagittarids/Capriconids meteor shower.
2. Total lunar eclipse: Earth as an exoplanet
On January 20, 2019, astronomers at the Leibniz Institute for Astrophysics in Potsdam (AIP), Germany used the total lunar eclipse to search for the ingredients for life in Earth’s atmosphere.
Why? To use Earth as the prototype of a habitable planet so scientists can learn what to look for in the atmosphere around exoplanets.
They used Arizona’s Large Binocular Telescope (LBT) and found oxygen water, sodium, calcium and potassium in the dimmed and polarized sunlight shining through the Earth’s atmosphere—and reflected onto the Moon during the total lunar eclipse.
The LBT was observing “Earthshine,” sunlight reflected from the Earth’s surface onto the Moon.
3. Total lunar eclipse: estimating the Moon to Earth radius ratio
Using just a smartphone, a telescope and a total lunar eclipse it’s possible to measure the the ratio between the Moon and the Earth radii.
That’s what two scientists in Santiago, Chile did on January 20, 2019 during the total lunar eclipse—and they published their results. Using a smartphone attached to a telescope, they took photographs of the cape of Earth’s shadow on the Moon.
With geometry and open-source software they then calculated the ratio between the radii of the Moon and the Earth—and got the same result as the known values. The conclusion? Smartphone cameras can be used to get powerful astronomical results.
When is the total lunar eclipse ‘Blood Moon?’
The next total eclipse of the Moon will occur on Wednesday, May 26, 2021. In the early hours of May 26, 2021 the western U.S. will see a full “Flower Moon” turn a reddish color for precisely 14 minutes and 30 seconds as our satellite briefly glides through the edge of Earth’s dark shadow in space.
Disclaimed: I am the editor of WhenIsTheNextEclipse.com
Wishing you clear skies and wide eyes.