A total solar eclipse is passing over South America: What to know

On Tuesday, a total solar eclipse will be stunning crowds across South America.

Buenos Aires, Argentina -- Nearly two years after the "Great American Eclipse" of 2017, another total solar eclipse is crossing the Americas. This time, it will be passing over Chile and Argentina on Tuesday, and crowds are preparing to be wowed as the moon passes directly in front of the sun.

While the area of greatest visibility, or longest duration, occurs over the South Pacific, there are a number of cities where the total eclipse will be visible, including La Serena, Chile; San Juan, Argentina; Rio Cuarto, Argentina and about 40 kilometers (24 miles) south of Buenos Aires.

Fast facts about eclipses:

There are four types of solar eclipses: partial, annular, total and hybrid. According to NASA, solar eclipses happen about twice a year, but total solar eclipses only occur every 12 to 18 months with varying visibility.

Since an eclipse happens when the sun, moon and Earth are in alignment, eclipses nearly always come in pairs of two or three, with a lunar and solar eclipse being partnered about two weeks apart. In this case, according to NASA, there will be a partial lunar eclipse visible on July 16 in parts of South America, Europe, Africa, Asia and Australia.

How to watch:

Be sure not to look directly into the sun without proper eye protection. You can likely find solar eclipse glasses at your local tienda if you're in the area, but NASA recommends checking to see that they're compliant with the ISO 12312-2 international safety standard and that they're not scratched or damaged.

Note that multiple pairs of sunglasses are not sufficient eye protection and you may risk eye damage. You shouldn't be able to see anything through the proper filters or glasses, except for the sun… perfect for eclipse gazing.

The one time it's safe to look directly at the eclipse without filters is during totality. For this brief moment, the moon will completely obscure the sun, and a ring will appear. This ring is called the penumbra, while the darkened moon is called the umbra.

As totality is ending, a bit of light will peek out from behind the moon, resembling a diamond ring. At this point, return to using eye protection. Happy viewing!