How do Baily’s beads form during a total solar eclipse?

Baily’s beads are an arc of bright spots that appear during a total or annular solar eclipse. They form just before the Moon’s disk completely covers the Sun, or immediately as it begins to reveal the Sun again.12

As the Sun is reduced to a very thin, narrow crescent, the remaining sunlight is broken into distinct segments by the irregular topography of the Moon’s edge, known as the limb. Mountains and valleys along this edge allow sunlight to pass through in specific locations, creating an array of bright specks that resemble a string of beads. These beads disappear at the moment of second contact, when totality begins, and reappear in reverse order at third contact.12

Because the Sun remains intensely brilliant during the partial phases when these beads are visible, it is essential to protect your eyes using appropriate filters to prevent permanent injury.2