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Get a sneak preview of Baily’s beads on the waning moon

Glowing crescent moon with white arrows pointing to the tips of the crescent where small dots of light are visible, labeled beads.
You don’t always need a total eclipse to see Baily’s beads. In this image of the waning crescent moon from April 5, 2024, the beads are visible as small pebbles of light at the tips of the crescent. Look for the same effect during the total solar eclipse on April 8, 2024. Image via Raúl Cortés.

Baily’s beads eclipse teaser

As many of you may know, a total solar eclipse exhibits a phenomenon referred to as Baily’s beads. This is sunlight passing through the rugged topography of the limb of the moon, showing up as pebbles of light. But, we can see them during a normal waning crescent moon phase, too! The photo above shows a waning crescent moon as we saw it in Monterrey on April 5, 2024. Here, at the very end of the “moon horns”, you can see the same – but opposite – effect as during a total eclipse.

During a normal lunar phase, the “beads” are high mountains or craters lit by the sun, and the dark spots between the beads are valleys. During a solar eclipse, it is just the opposite. The beads are created by sunlight going through valleys, while the dark spots are high mountains.

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The very tip of the glowing crescent moon. A line of dots of light labeled Beads is visible.
A zoomed-in look at the crescent horn, showing how light seeps through the rugged terrain of the moon limb as beads. Image via Raúl Cortés.
Very closeup view of tip of glowing crescent, with a row of dots extending from it.
A zoom in of the lower part of the crescent horn, showing the Baily’s beads effect. Image via Raúl Cortés.

Bottom line: These photos of the crescent moon give us a sneak peak of the Baily’s beads phenomenon, which will be visible during the total solar eclipse on April 8.

April 6, 2024
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