This week, a rare hybrid solar eclipse will darken skies across the South Pacific, with narrow portions of Australia, East Timor and Indonesia being bathed in complete shadow.
The event is a combination of different types of solar eclipses—it will first appear as an annular eclipse with the moon wrapped in a fiery halo of sunlight, then shift into a total, sky-darkening eclipse and finally return to the annular “ring of fire.”
Hybrid solar eclipses are few and far between: The last one was in 2013, and the next will be in 2031. One of these phenomena will not appear over the contiguous United States for more than a century—until March 2164. That makes this week’s eclipse a must-see for cosmic enthusiasts.
But for those who can’t experience it in person, several free live streams will air coverage of the spectacle online. The hybrid eclipse begins at 9:34 p.m. Eastern time on April 19 and lasts until 2:59 a.m. on April 20.
Solar eclipses occur when the moon passes directly between the sun and the Earth. But although the moon orbits Earth once every 27.3 days, an eclipse does not happen with every revolution—since the moon’s orbit is tilted by five degrees relative to Earth’s, it usually appears to pass above or below the sun from our point of view.
But on the special occasions when the moon and sun do align in the sky, one of four spectacular outcomes can happen: an annular, total, partial or hybrid solar eclipse. An annular eclipse with a ring around the moon occurs when the moon is farther from the Earth and appears smaller than the sun in the sky. In a total eclipse, the moon is in full alignment with the sun, blocking the entirety of the star’s brightness and casting a shadow over parts of our planet. A partial eclipse happens when the sun is only partly covered by the moon. And a hybrid eclipse is a combination of these other types.
These differences exist because the moon’s orbit is not a perfect circle, but rather an oval-shaped ellipse. As a result, it passes between the Earth and sun at varying distances, creating a visual effect of a larger or smaller moon. During a hybrid eclipse, different vantage points on Earth see the moon appear as different sizes due to our planet’s curved surface putting some viewers farther from the moon, writes Time’s Jeffrey Kluger. In this way, a total eclipse and an annular eclipse can be seen in different places around the world.
This week, the hybrid eclipse will occur as a combination of all three other types of eclipses. The annular eclipse will first appear over the Pacific south of Madagascar, then switch to a total eclipse while still over water. Totality will sweep across Earth to the northeast—passing over small regions of Australia, East Timor and Indonesia—and shift back to an annular eclipse between Indonesia and Hawaii. The annular portion of the eclipse will not be seen from land. At some angles, such as from Papua New Guinea and the Marshall Islands, only a partial eclipse will be visible.
In Australia, the largest inhabited place that will experience a total eclipse is the small town of Exmouth. Though its population is only about 2,800, thousands of viewers will flock there to glimpse this rare solar event.
“I look forward to this eclipse, because it is a long-anticipated party,” heliophysicist Jia Huang of the University of California, Berkeley, tells Popular Science’s Briley Lewis. “A hybrid eclipse is very rare.”
To catch this phenomenon from afar, tune into an online livestream. TimeAndDate.com will host one on YouTube beginning at 9:30 p.m. Eastern time on April 19. NASA will also air the eclipse on NASA TV from 10:30 p.m. And the Gravity and Discovery Center and Observatory will stream from Exmouth at 10 p.m., showing totality beginning at 11:29 p.m.
Even if internet-based skywatching does not strike your fancy, you can plan to catch next year’s total solar eclipse, which will cross North America following a path from Mexico to eastern Canada in April 2024. And this week, the Lyrid meteor shower is illuminating the night sky—the spectacle will reach its peak on Saturday with about 18 meteors visible per hour.