The most exciting part of a total solar eclipse happens fast — within minutes — so make sure you're ready, whether you're on the ground or watching live online.

Getty/Rob Stothard

Source: NASA

If you live in parts of Southeast Asia, like Indonesia, you might see the full total eclipse with your own eyes.

Reuters/Toru Hanai

And if you’re in the Pacific — including Hawaii, Guam, and parts of Alaska — you might see a still-exciting but less dramatic partial solar eclipse. But more on this later.

AP

Here's what’s going to go down.

A total solar eclipse happens when the moon, sun, and Earth are perfectly aligned — causing the moon to cast two narrow shadows across our planet.

NASA Goddard Media Studios

The moon orbits Earth on a slanted plane, at a slight angle. Total solar eclipses happen only when the orbit of the earth and moon are completely in line, about once every 18 months (on average).

 Source: NASA Scientific Visualization Studio

Eclipses happen in incremental stages as the moon swoops around Earth. This photo is shortly after "first contact" — when the moon first "touches" the disk of the sun.

REUTERS/Abdel-Halim Shahaby

From there the moon slowly glides in front of the sun until it covers the star ("second contact"). Right before that happens, rays of sunlight scatter through the craters and valleys on the moon's surface. This visual phenomenon is referred to as Baily's Beads.

Miloslav Druckmüller/NASA

Source: NASA

As the moon edges close to totality, those brilliant beads around its edges will begin to disappear, leaving only one shining spot above the surface of the sun, which is said to look like a diamond ring.

Miloslav Druckmüller/NASA

Source: NASA

If you're watching from outside, make sure you're wearing your eclipse glasses because the sun's rays can damage your eyes — even during this partially obscured stage.

Bill Ingalls/NASA

As the moon continues along its path, the glistening "diamond" will disappear and eventually there will be no direct sunlight streaming around its surface.

Miloslav Druckmüller/NASA

Source: NASA

Thus begins the money shot: A total solar eclipse.

Luc Viatour/www.Lucnix.be

Source: NASA

At this point, it's safe to look directly at the sun without glasses, when the eclipse is in this complete totality phase.

Flickr / David Goehring

Source: NASA

And don't hesitate because this phase will only last for a minute or two.

Navn on YouTube

Source: NASA

If you're extra lucky, you might see a giant loop of plasma , called a solar prominence, protruding from the sun during totality. You can see part of a prominence at right in pinkish-red, below:

Luc Viatour/www.Lucnix.be

Here's the path the shadow will take during the March 8 eclipse:

Source: NASA

The darkest and narrowest part of the shadow is called the umbra.

NASA

Those lucky enough to be in the direct path of the umbra shadow will be able to see the full total eclipse.

NASA's Goddard Space Flight Center/E. Wright

The umbra will be 97 miles wide and crawl 8,800 miles across the Earth over a few hours. If you're in range, you'll see an eerie twilight wash over the sky for the few minutes during totality. The temperature will drop a few degrees, too.

Source: NASA

You'll also have the rare and mystifying opportunity to see the solar corona — an aura of dancing streamers, plumes, and loops of the sun's blazing hot plasma.

NASA’s Goddard Space Flight Center/Duberstein

Source: NASA

But don't fear, even if you're not within the narrow path of totality. You can still see a partial eclipse in the second, much wider shadow called the penumbra.

NASA

Source: NASA

The penumbra will fan across Asia, Hawaii, Guam, and parts of Alaska.

NASA's Goddard Space Flight Center/E. Wright

Source: NASA

You may be wondering how the sun is completely obscured, since the moon is much smaller than the sun — about 400 times smaller, in fact.

NASA/SDO/LRO/GSFC

By coincidence, the moon also happens to be 400 times closer to Earth: a perfect match! Most of the time, this allows it to completely block the sun's rays.

NASA/SDO

But the moon's imperfect orbit makes it wobble — or librate — toward and away from the Earth. This sometimes makes it a bit farther away and appear smaller during an eclipse.

Source: NASA

If it's on the smaller side, you get an annular solar eclipse, like this one:

The next total solar eclipse is slated to happen on August 21, 2017. And lucky for the US, this one’s supposed to swoop right across the states. It will be the first total eclipse visible from the US since February 26, 1979.

Source: NASA

>> Watch the eclipse live online

Not in the path of the eclipse?

We've rounded up two of the best live webcasts for your viewing pleasure here, by NASA Television and Slooh.

Slooh's live coverage starts at 6 p.m. ET (this broadcast will show the eclipse live first), and NASA TV starts coverage at 8 p.m. ET.