The early May skies have been spectacular so far as the Eta Aquari meteor shower, the signature of the famous Halley’s Comet, has pierced our atmosphere. But there’s another reason to keep an eye on the stars in the coming days. It is a mysterious phenomenon known as Earthshine.
Earthshine, known as the “Glow of Ashes,” the “Old Moon in the Arms of the New Moon,” or “Da Vinci’s Sparkle,” has captivated onlookers for thousands of years. Now is the perfect time to catch a glimpse of this event.
When can I see Earthshine?
Weather permitting, you’ll be able to see Earthshine tonight. Thursday, May 9thjust after sunset (8:37 PM BST in London, 8:01 PM EDT in New York City, and 7:44 PM PDT in Los Angeles).
There’s a new moon (where the moon is between the Earth and the sun), and right after this event is the best time to catch a glimpse of the Earthshine effect.
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Now, the only part of the moon that will be illuminated by the sun will be a small crescent (or more accurately, the waxing moon), making the Earthshine effect visible.
There are two reasons why the Earthshine appears brighter when the Moon is crescent.
First, only the thin crescent moon on the Moon’s surface is illuminated by sunlight, so there is less competition for faint Earthshine. It’s similar to how a flashlight can see better in a dark room than in a bright room.
Second, during this crescent phase, the Earth is almost completely illuminated when viewed from the Moon. Imagine yourself standing on the moon. You will see a bright, nearly perfect Earth casting Earthshine onto the Moon’s surface.
Here’s how the moon will look over the next few nights:
- May 9th: 3% Waxing Crescent Moon
- May 10th: 7% Waxing Crescent Moon
- May 11th: 14% Waxing Crescent Moon
- April 12: 22% crescent moon
Weather permitting, you should be able to see Earthshine on all of these nights (but the night closest to the new moon on May 8th is best). For the best chance of seeing it, look for it in a dark area just after sunset.
April and May are the best times of the year to observe the Earthshine effect, so this may be your last chance to observe it until next year.
What is Earthshine?
Earthshine is the faint glow on the unlit side of the moon that is visible around a new moon. Essentially, it’s light from the Earth rather than the Sun, which reflects off the Moon like a giant cosmic mirror.
The process looks like this:
- Sunlight hits the earth and reflects off the ocean, land, and clouds.
- Some of this reflected light returns to space.
- A small portion reaches the moon and illuminates the side facing us that is hidden from the sun’s direct light.
This light travels long distances, first reaching the Earth and then the Moon, so it is much dimmer than the parts illuminated by the sun. This gentle indirect glow is called Earth Shine.
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Why is now the best time to watch Earthshine?
During spring, currently especially noticeable in the Northern Hemisphere, Earthshine becomes approximately 10 percent more pronounced due to the increased reflectivity of the Earth’s surface.
“Earth’s reflectivity, or albedo, changes throughout the year. Snow and ice reflect a lot of sunlight, but land and the vegetation on it reflect less light. Like water, , our oceans become even less reflective. Dr. Darren Baskill To tell BBC Science Focus.
As the northern hemisphere tilts toward the sun after winter turning its back on the sun, the remaining snow and ice in the polar regions acts as a reflective surface, bouncing large amounts of sunlight back into space.
This reflected light reaches the moon’s surface and projects Earthshine onto its dark side.
By next month, most of the snow and ice will be gone, making Earthshine a little harder to find, especially for those of us who live in artificially lit urban areas.
“Additionally, as spring turns to summer, the ‘young’ crescent moon will be higher in the sky, making it easier to observe the phenomenon,” Baskill added.
What does da Vinci have to do with it?
Among his many accomplishments, Leonardo da Vinci was one of the earliest to accurately describe Earthshine, leading to the phenomenon now often referred to as the “da Vinci glow” (although (He did not coin the term himself.)
Da Vinci meticulously sketched the moon and various celestial bodies, and correctly deduced that Earthshine probably resulted from sunlight reflecting off the Earth.
However, his theory was not without flaws. He initially attributed the influence primarily to oceans, overlooking the significant contribution of winter snow and ice.
Before da Vinci, some astronomers thought the moon might be translucent, allowing sunlight to pass through it. This theory suggested that when sunlight hits the moon from behind, it shines more easily through the thin rim, creating a brighter crescent and dimmer earthshine.
What will affect Earthshine?
As mentioned earlier, the brightness of Earthshine is affected not only by the presence of snow and ice, but also by various other factors.
One important factor is cloud cover, as clouds can reflect or absorb sunlight. Thick, white clouds are particularly effective at reflecting sunlight, increasing Earth’s illumination. Generally, as the amount of clouds on Earth increases, Earthshine will appear brighterOf course, this assumes the moon is still visible.
In 2017, scientists uncovered a worrying trend. Earth’s albedo, or overall reflectance, is decreasing Over the past few decades. This decrease suggests that Earthshine is becoming less visible.
Such phenomena could signal that global warming is intensifying, as more heat is absorbed by Earth’s oceans and atmosphere, leading to less sunlight being reflected back into space. .
Did you know that?
- When the sun suddenly disappears, the crescent moon disappears first, but Earthshine dimly illuminates the moon for an additional three seconds.
What equipment do I need to watch Earthshine?
In short, not that much. Eyes are enough.
If you want to further your viewing experience, binoculars can help you find hidden details on the moon’s surface.
About our experts
Dr. Darren Baskill I am an outreach officer and lecturer in the School of Physics and Astronomy at the University of Sussex. He previously lectured at the Royal Observatory Greenwich and was the organizer of the annual Astronomical Photographer of the Year competition.
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Source: www.sciencefocus.com
