You may have noticed the Moon exhibiting a ghostly glow of late, where subtle light illuminates the usually dull part of the lunar surface. This is a phenomenon called Earthshine, and it can be a spectacular sight, not to mention a great opportunity for lunar photography.
In this article, we explain when you can see this moonglow, what causes it, and why it's named after one of the most celebrated scholars of all time.
You can also take advantage of clear nights this year with ourfull moon uk calendaryastronomy guide for beginners.
When can I see Earthshine?
Weather permitting, you can watch Earthshine tonight,May 22nd, after sunset (8:56pm BST in London, 8:13pm EDT in New York City).
Earthshine is visible in the mornings a few days before the new Moon and in the evenings a few days after the new Moon. You may have already seen it before dawn on May 17 during the waning crescent phase, but if you didn't feel like getting out of bed at that time, we have another chance during thehair removalphase of the crescent moon.
Here are the next opportunities to see Earthshine:
- May 21th:Illuminated crescent moon at 3.9%
- May 22nd:Crescent moon illuminated at 8.9%
- may 23:15.5% illuminated crescent moon
"Take a look on the night of May 23 and you can see the crescent Moon between the bright planet Venus and the star Pollux, with the red planet Mars just to the left of the pair," he advises.Dr. Darren Baskill, Professor of Astronomy at the University of Sussex.
The phenomenon is most visible during the waxing or waning phase, because the illuminated part of the Moon is thinner, allowing more of the darkened Moon to be illuminated by Earthshine.
It is the ideal time of year to see, since during the spring, the northern hemisphere is tilted towardsSun, while at higher latitudes, persistent winter snow and ice still provide ground cover. Snow and ice reflect more light than darker colored vegetation and water (ie, snow and ice have a higher albedo), so we get a more apparent Earthshine.
While Earthshine is expected to be brightest during the winter months when snow and ice cover is prolific, the amount of light reaching the Arctic is significantly less, so Earthshine is not as hectic during winter.
Bottom line: get out there and watch it while you can!
What exactly is earthshine?
Earthshine appears as a soft, subtle glow on the unilluminated or "night" portion of the Moon during specific phases. This is when a delicate, yet somehow ghostly shape of the full Moon nestles in the arc of the brilliant crescent Moon, and it's a beautiful sight for those early summer nights.
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Also known as the Da Vinci glow, the intensity ofThe brightness of the earth can vary depending on certain factors., such as atmospheric conditions, the reflectivity of the Earth, and the location of the observer.
Just keep in mind that the popular media says that the "dark side of the Moon is visible" as this is incorrect; the dark side of the Moon is facing away from us.
how is the moontidal lock, we will never be able to see the dark side of the Moon from our point of view here on Earth. Rather, we can see theoffpart.
What causes it?
Earthshine is also known as Da Vinci's shine, ashen shine, or rather, romantically, "the old moon in the arms of the new moon." It is caused by sunlight reflecting off the Earth's surface and then reflecting back to the Moon.
"Like all planets and moons, Earth does not emit light, it only reflects light from the sun," Baskill explains.
"This reflected sunlight can be seen illuminating the darkest part of the Moon for a few days on either side of a new Moon, when the Moon appears as a crescent in the evening or morning sky.
"The crescent moon is caused by bright sunlight directly illuminating the Moon, while the darker part of the Moon is dimly illuminated by Earthshine, sunlight that has been reflected from Earth to illuminate gently the moon".
Earthshine occurs during the phase of the lunar cycle when only a thin crescent of the Moon is illuminated bystraightsunlight, either in the waxing or waning phase.
As for the part of the Moon that is not illuminated by direct sunlight, this is the part that we see as a ghostly glow. As we all know, light from the Sun reaches the Earth and illuminates its surface. But this is not limited to landmasses, as it also includes clouds, oceans, and the atmosphere.
some of thisluzit is then scattered, diffused, and reflected back into space. A part of this reflected light travels towards the Moon and lands on its unilluminated part, the lunar night side.
The Moon, despite having a non-reflective surface, bounces this reflected sunlight from Earth. And it is this phenomenon that results in a dim glow on the unilluminated part of the Moon, providing subtle illumination to the otherwise dimly lit lunar surface.
What affects it?
Earthshine's appearance and intensity is influenced by several factors, including Earth's cloud cover, the composition of its atmosphere, and the angle of sunlight reflecting from our planet onto the Moon. These factors can cause slight variations in the brightness and color of the earth glow, making it different every time.
Earth's atmosphere, for example, plays a crucial role in shaping Earthshine's appearance. As light from the Sun passes through the atmosphere, it undergoes scattering and absorption, and different wavelengths are affected to varying degrees. This atmospheric filtering influences the color and intensity of Earth's glow, and it is this light that is ultimately reflected back to the Moon.
Different ground covers will reflect different amounts of light; for example, the earth reflects about 10-25 percent, while clouds reflect about 50 percent of the light.
Why is it called the da Vinci glow?
In the early 16th century, Renaissance scholar Leonardo da Vinci turned his thoughts to unraveling the enigma of this strange, otherworldly glow. He made detailed drawings and sketches of the Moon, and although da Vinci did not coin the term himself, these observations led to its association with his name.
His notebooks contained a drawing depicting Earthshine, which is now held in theleicester codex, a compilation of Da Vinci's scientific writings. Although you will need patience if you want to read the manuscript yourself, since da Vinci recorded his observations in his characteristic mirror writing; Italian backwards.
What equipment do I need to see Da Vinci's Shining?
Other than the ever-constant desire for clear skies, no special equipment is required. If you have some on hand, although it's not necessary, using binoculars or a telescope can help you pick out features you couldn't normally see on the Moon's surface and look at subtle variations in brightness more closely.
You can even try drawing the Moon on dark paper with chalk, pastels, or pencils.
Will climate change affect our ability to see it?
Potentially. Researchers looking at the Earth's albedo have discovered thatwarming temperatures may result in a less intense Earthshine.
As the oceans warmed, they found that fewer low clouds were forming over the eastern Pacific Ocean, west of the Big Bear Solar Observatory in California, where they were taking measurements. This reduction in cloud cover led to a slight decrease in the Earth's albedo (reflectivity), subsequently affecting the intensity of the Da Vinci glow.
About our expert
Dr Darren Baskill is an Extension Officer and Professor in the Department of Physics and Astronomy at the University of Sussex. He previously lectured at the Royal Greenwich Observatory, where he also launched the annual Astronomy Photographer of the Year competition.
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