Baily's beads are points of sunlight shining through valleys on the Moon's rugged edge in the last seconds before totality and the first after it. They are named after the English astronomer Francis Baily, who described them at an annular eclipse in 1836. Each bead is direct sunlight, so watch through eclipse glasses.
Understanding Baily's Beads
What makes the beads
The Moon's edge, seen side on, is a skyline of mountains several kilometres high and the valleys between them. When only the thinnest crescent of the Sun is left, that skyline decides where the light gets through, so the pattern of beads is different at every eclipse and changes second by second. Spacecraft maps of the Moon's surface now let astronomers work out the profile of its edge for any eclipse, and with it where the beads will appear and how long they will last.
The sequence at second and third contact
Baily's beads come just before the diamond ring at the start of totality and just after it at the end:
| Moment | What you see | Eye protection |
|---|---|---|
| Seconds before C2 | The crescent breaks into Baily's beads | Glasses on |
| Just before C2 | The diamond ring: one last bead beside the corona | Glasses on |
| C2 to C3 | Totality: the corona, prominences, darkness | Glasses off |
| Just after C3 | A second diamond ring, then beads | Glasses back on at once |
Beads at the edge of the path
Near the northern or southern limit of a path of totality, the Moon's edge runs along the Sun's instead of crossing it, so beads can flicker on and off for many seconds, sometimes for the whole of a short totality. Some observers go to the edge on purpose, trading minutes of totality for a long show of beads and the pink chromosphere. The contact times on each city page show how long totality lasts there.