On Monday, August 21, millions of people will experience total darkness during the day as a solar eclipse moves through the United States. Just before totality — the term used to describe the minutes of complete darkness when the moon crossing in front of the sun — you may be able to see Baily’s Beads.
Baily’s Beads occur because the moon’s surface isn’t smooth. The edge of the moon is riddled with various bumps, craters, and mountains, which interfere with the light sun’s shining through. These peaks on the moon’s edge cause the breaks of light known as Baily’s Beads.
Baily’s Beads can only be seen for a few seconds before the moon completely covers the sun. In those moments, you will be able to see a ring around the sun break into beads that is sometimes compared to a glistening necklace.
“In an annular eclipse, Baily’s beads first appear along the sun’s trailing, rather than leading limb, pinpointing the moon’s deepest limb depressions first and marking second contact. The beads increase in number as the limb moves further onto the sun’s disk until no breaks in the sun’s rim are visible. When the moon’s leading limb reaches the opposite rim of the sun, the beads return, then diminish in number as they merge together until the last one vanishes when the moon’s limb appears unbroken, marking third contact.”
In order to see Baily’s Beads, you’ll want to make sure you are wearing solar eclipse glasses. Look toward the eastern edge of the moon to see the light break into “beads” before the sky goes completely dark.
The Beads were named after Frances Baily, an English astronomer who first spotted them during a solar eclipse that took place on May 15, 1836, in Roxburghshire, Scotland. In 1842, he travelled to Pavia, Italy, to watch another total solar eclipse. According to Wards Book of Days, it was Baily’s discoveries and publications that made eclipse watching popular among the “scientific community.”