About 20,000 skygazers descended on the small resort town of Exmouth on Western Australia’s North West Cape last Thursday to experience a wondrous celestial phenomenon — a total solar eclipse that looked remarkably like a diamond ring.
The Diamond Ring Effect, which was first explained by Francis Baily in 1836, occurs when the Moon completely masks out the Sun during a solar eclipse. Due to the rugged lunar landscape, the black outline of the moon is not smooth. Tiny beads of sunlight can still shine through in some places and not in others as the moon slowly grazes past the sun.
These are called Baily’s Beads. When only one dazzling “bead” remains, momentarily, the view of the eclipse resembles a diamond ring. The ring’s glow is produced by the Sun’s corona remaining dimly visible around the lunar silhouette.
The Diamond Ring Effect can be seen in the instant just before the total solar eclipse and in the moment just after. In Australia, the Diamond Ring was visible for only a second or two, while the eclipse lasted about a minute.
NASA astronomer Henry Throop was one of the thousands cheering the daytime blackout, explaining to an NPR reporter that the experience was "mind blowing."
"I feel so emotional, like I could cry," added Fremantle, Australia, native Julie Copson.
Solar eclipses are the result of an uncanny mathematical coincidence. The Moon is 400 times smaller than the Sun, but is 400 times closer to the Earth. This results in two celestial discs that are virtually the same size visually.
On occasion, solar eclipses will occur when the Moon, in its elliptical orbit, is near its farthest point from Earth and appears slightly smaller than average. In that case, the halo of the Sun is more prominent and the Diamond Ring Effect doesn't occur. Instead, we are treated to a “ring of fire” solar eclipse — also known as a "wedding band in the sky."
Scientists described this type of eclipse as “annular,” a word derived from “annulus,” which means ring-like object.
While Exmouth (pop. 3,000) had been touted as the best place in Australia to see Thursday's solar eclipse, the spectacular show was also visible in parts of Indonesia and East Timor.
The next total solar eclipse over North America will take place on April 8, 2024. The next annular eclipse over North America is set for October 14, 2023.
The image, above, was captured by NASA at an observatory in Chile in 2019. Thursday's eclipse was live-streamed by NASA, but the videographer was not able to get a clear shot of the Diamond Ring Effect.
Credit: Image by NASA/Goddard/Rebecca Roth NASA Goddard Space Flight Center from Greenbelt, MD, USA, CC BY 2.0, via Wikimedia Commons.