This weekend, a full Flower Moon will appear in the night sky as a total lunar eclipse turns our natural satellite red.
Full moons are a lunar phase that occur roughly once every month when our natural satellite is located opposite to the sun, with the Earth in between.
During a full moon, the side of the moon that faces towards our planet is fully illuminated, appearing like a perfect circle. The full moon this month will be visible on the night of May 15-16.
The full moon in May is often referred to as the “Flower Moon.” But where did this name come from?
The names given to the full moons originate from a number of places and historical periods, including Native American, colonial American and European sources.
This name has been attributed to Algonquin peoples, and refers to the fact that this time of year is characterized by the growth of spring flowers in North America, according to The Old Farmer’s Almanac.
May’s full moon will be also be very close to its perigee—the point in the moon’s orbit when it is closest to Earth—and can be described as a “supermoon” as a result. The moon has an elliptical orbit around the Earth, meaning the distance between it and our planet varies over time.
Supermoon is a non-scientific term and there are several ways to define it. But perhaps the most common definition refers to any full moon that occurs when the moon is at least 90 percent of perigee, according to The Old Farmer’s Almanac.
What Happens During a Total Lunar Eclipse?
The Flower Moon also coincides with a total lunar eclipse, which occur when the moon is on the opposite side of the Earth from the sun, and the Earth’s shadow falls on the moon. Lunar eclipses only occur at the full moon phase.
“A total lunar eclipse happens when the moon moves into the Earth’s shadow,” Robert Massey, deputy executive director of the U.K. Royal Astronomical Society, told Newsweek. “So, it’s effectively that the moon, the Earth and the sun are almost exactly in line. Now, it doesn’t happen every month, because the moon’s orbit around the Earth is tilted with respect to the Earth’s orbit around the sun.”
“Most of the time the moon goes above or below the shadow,” he said. “But every so often, perhaps a couple of times a year, it actually goes into the shadow. And so you have an eclipse.”
The moon doesn’t fully disappear during a total lunar eclipse because the shadow isn’t completely dark. In fact, during the total phase of the eclipse, some of the sun’s light is refracted through the Earth’s atmosphere, which has the effect of turning the moon a shade of red. This is why the moon during a total lunar eclipse is sometimes referred to as a “blood moon.”
“Imagine sunlight going through the Earth’s atmosphere, the atmosphere bends [the rays] a bit. And because of the angle, what you see is very red light,” Massey said.
“If you imagine the color of the sun at sunset—if it’s very low down, it goes that deep red color—that’s the quality of light that hits the moon. So, on Earth, you can get quite a very pretty effect whereby you get the moon appearing in different shades of red, depending on how deep in the shadow it is. It is actually quite deep this time so it will probably be a pretty pronounced dark red.”
Before the total phase of the eclipse, observers will see the moon entering the lighter part of the Earth’s shadow (penumbra)—the only sign of which will be a very light dimming. The moon then starts to enter the darker part of the Earth’s shadow (umbra) and it will dim noticeably.
Finally, during the total phase, the whole of the moon will be inside the umbra and it will turn red. After this, the process reverses itself until the moon appears like a normal full moon again.
The total phase of the upcoming eclipse will be visible across most of the Americas—except for the northwesternmost part of the continent—the western edge of Europe, western parts of Africa, and the Antarctic on the night of May 15-16. In fact, the United States has one of the best views of this eclipse, according to Massey, at least for the people in the lower 48 states.
When Was the Last Lunar Eclipse?
The last total lunar eclipse occurred on January 20-21, 2019. But the last eclipse of any kind took place on November 18-19, 2021, but it was only a partial one. Partial lunar eclipses occur when the full moon passes only partway into the umbra.
What Is the Next Full Moon?
The next full moon will be visible in the evening of June 14, according to The Old Farmer’s Almanac. The full moon in June is often referred to as the Strawberry Moon, among other names.
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