Solar Eclipse 101

A total solar eclipse happens somewhere on Earth once every year or two. What is an eclipse? Learn more about how solar eclipses happen, the four types of eclipses, and how to view the sun safely if you're within the path of totality. Eclipse map adapted with permission: https://www.exploratorium.edu/eclipse

Lucky skywatchers in Southeast Asia get a rare front-row seat to a total eclipse on March 8 and 9, and Pacific islanders will see a still-dazzling partial eclipse. But the rest of the world doesn’t have to miss out: If you can’t hop a plane to the middle of the Pacific Ocean, you can watch it live online.

(Just come back to this page and scroll down to see our handy video feed, below.)

The moon passes between Earth and the sun every month, but a total solar eclipse happens only when the three celestial bodies are perfectly aligned. And this particular eclipse is even more special: It’s happening while the moon is at its closest point to Earth—called perigee—making the moon appear larger in the sky, as a “supermoon.”

The moon casts its dark central shadow, called the umbra, onto a very narrow strip along the surface of the Earth. The strip from which the upcoming total eclipse will be visible lies mostly over the Pacific Ocean.

Over the course of about three hours, the moon's dark shadow first touches land over Sumatra, Indonesia, at 6 p.m. EST Tuesday evening in North America (Wednesday in Indonesia).

The path of the totality—where the entire face of the sun is covered—then races across central Borneo, Sulawesi, and moves across the International Date Line into March 8. The shadow will pass quickly northeastward across the Pacific Ocean until vanishing near Hawaii.

In total, the moon's shadow will travel a path approximately 8,800 miles (14,162 kilometers) across the globe, while the width of the path will be no more than 97 miles (156 kilometers) across.

Along this thin track of totality, broad daylight will briefly turns into twilight. This darkness will last the longest at Woleai Atoll, Micronesia: a whopping four minutes, compared to just two in Eastern Indonesia.

Though the most dramatic parts of this celestial phenomenon will be visible in remote areas, armchair astronomers can watch a live webcast of the eclipse by the robotic telescope service SLOOH.com.

Slooh will beam multiple feeds from the Pacific Basin region along the path of totality, including coverage from the Indonesian countryside.

Where will the partial eclipse be visible?

Partial phases of the eclipse—where only part of the sun is covered by the lunar disk—will be visible across a much wider area, including China, the Koreas, Japan, Philippines, Guam, northern Australia and even parts of Alaska.

From example, from Honolulu, Hawaii as much as 63 percent of the sun will be eclipsed just before sunset on Tuesday, at 5:37 p.m. local time.

What’s the best way to watch this event?

For observers along the path of the eclipse, astronomers recommend using either a professionally manufactured solar filter in front of a telescope or camera, or eclipse-viewing glasses that sufficiently reduce the sun's brightness and filter out damaging ultraviolet and infrared radiation.

(Check out a DIY alternative: Build an eclipse viewer).

What if I miss this one?

Later this year, on September 1, there will be another solar eclipse visible from Africa.

Folks in North America will have to wait their turn, however, as the next total solar eclipse will occur for them on August 21, 2017. The shadow path will cross over the contiguous United States for the first time since 1979, from Oregon to South Carolina. A much larger area of the continent will witness some degree of a partial eclipse.

Follow Andrew Fazekas, the Night Sky Guy, on Twitter, Facebook, and his website.

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