Rare hybrid solar eclipse to grace Exmouth next week; rest of Australia sees partial view

On April 20, a rare celestial alignment will cast a shadow across Western Australia, and thousands of people are already making their way to a small, remote town called Exmouth to witness it. For fifty-eight seconds, the Moon will slide directly in front of the Sun, blocking it completely from view. This will happen nowhere else in Australia. Everywhere else in the country will see only a partial eclipse—the Moon nibbling at the Sun's edge but never fully obscuring it.

What makes this event unusual is that it is a hybrid eclipse, a phenomenon so rare that it accounts for only about three percent of all solar eclipses. The last one occurred in November 2013. The next will not happen until November 2031. A hybrid eclipse occurs when the Moon reaches a very precise distance from Earth—close enough that its shadow behaves one way in some places and another way in others. As the eclipse path travels from near Antarctica northward, it begins as an annular eclipse, where the Moon is too far away to completely block the Sun and a ring of light remains visible. As the shadow moves north and passes over Exmouth, the geometry shifts and the eclipse becomes total. Then, as it continues toward the Pacific, it reverts to annular again. This transition happens because of the curvature of the Earth itself. "The rarity of this eclipse occurs because the distance has to be exactly right," explained astronomer Jonti Horner of the University of Southern Queensland. If the Moon were even slightly closer, the entire path would see a total eclipse. If it were slightly farther, everyone would see an annular eclipse.

Exmouth sits directly beneath the shadow's path, a narrow corridor only about forty kilometers wide. The eclipse there will unfold over nearly three hours, beginning at 10:04 in the morning and ending just after 1 p.m. Western Australian time. Totality itself—that moment when the Sun vanishes completely—will last just fifty-eight seconds. It is, as Horner noted, quite a short eclipse. The longest total eclipse ever recorded lasted seven minutes and thirty-two seconds, so what Exmouth will experience is a brief but complete darkness at midday.

The rest of Australia will see something far less dramatic. In the far north and west, the coverage will be substantial. Darwin will experience an eighty-one percent eclipse, enough that the Sun will become a thin crescent and the sky will take on an eerie quality. Perth will see seventy-one percent coverage. But as you move east and south, the effect diminishes rapidly. Adelaide will see only twenty-one percent. Brisbane, sixteen percent. Sydney, Melbourne, Canberra, and Hobart will all see less than eleven percent. Tasmania, at the southern tip of the continent, will see just five percent of the Sun covered. In these eastern and southern regions, most people will not notice anything at all. Our eyes are poor judges of subtle changes in brightness. When the Sun is half covered, the landscape receives fifty percent less light, yet it looks essentially the same. The scenery around you appears unchanged, and the difference goes undetected.

This eclipse is the first of five that will cross Australia over the next fifteen years. The next total eclipse, in July 2028, will cut a path from the Kimberley down to Sydney and will last five minutes and ten seconds at its peak—far more dramatic than what Exmouth will witness. After that will come a total eclipse across the southeast in 2030, an annular eclipse through Tasmania in 2035, and another total eclipse across central Australia in 2037. But for now, all eyes are on Exmouth, where a rare alignment of Sun, Moon, and Earth will create a moment of complete darkness in the middle of the day.