Late on Tuesday afternoon, the moon will block out the sun in South America.
Millions of people living in cities from La Serena, Chile, to San Juan, Argentina, will witness the event as shadows spread over hills and an uncanny coolness invades deserts. Many more have ventured to the region specifically for the spectacle — one that some astronomers are calling the Great South American Eclipse.
The celestial phenomenon is the first total solar eclipse since August 2017, generating excitement among professional astronomers, eclipse chasers and casual observers because it offers the opportunity to see pale tendrils of the sun’s atmosphere, or corona.
“We only get a few minutes to see the solar corona during an eclipse,” said Ivo Saviane, an astronomer at the La Silla Observatory situated on the outskirts of the Chilean Atacama Desert. “But this is a great chance to see the corona shoot ultrahot gas and study mechanisms like solar wind, which are still quite mysterious,” he said.
Here’s all you need to know to about the best times and places to watch the eclipse in-person and online.
When does the eclipse start?
The eclipse will start above the southern Pacific Ocean at 12:55 p.m. Eastern time and then arc toward the western coast of Chile. As the moon bites into more of the sun, daylight will slowly become dimmer.
La Serena, Chile, a city of about 200,000 people, will be the first in South America to experience the peak eclipse, or totality, at 4:38 p.m. Eastern time (the time zone is the same in Chile). Late Tuesday morning, The Associated Press reported that more than 300,000 visitors had gathered in the city for eclipse-watching, placing strain on its water and gasoline supplies as well as other city services.
Totality there will only last one or two minutes. Then the eclipse will barrel east.
Which places are in the eclipse’s path?
The path of the totality will track a strip of land about 90 miles wide, from La Serena to Chascomús, a city just south of Buenos Aires, Argentina.
The luckiest eclipse viewers may be people at Chile’s La Silla Observatory, situated on a mountaintop in the Atacama Desert. The area’s climate makes it more likely that it will be free of pesky clouds when totality begins there at 4:39 p.m. Eastern.
Chile’s foreign ministry posted pictures on Twitter showing clear skies around the observatory, where the country’s president, Sebastian Piñera, plans to take in the spectacle.
But not everyone seeking a good view will need to trek out to the desert or up a mountain.
“The sun will be about 14 degrees above the horizon at the time of the total eclipse, so it will be really low,” Dr. Saviane said. “That means you can see the eclipse from anywhere, as long as there are no clouds obstructing your view.”
Skywatchers in Chascomús, Argentina, will be the last with a chance to see the totality, at 4:42 p.m. Eastern (or 5:42 p.m. local time in Argentina). But weather reports showed cloudy conditions there in the afternoon.
After that, the eclipse will head into the Atlantic Ocean and effectively end when the sun sets around 4:50 p.m. (5:50 p.m. local time).
Outside the path of totality, people will be able to see a partial eclipse in the rest of Chile and Argentina as well as in Ecuador, Peru, Bolivia, Paraguay, Uruguay and even parts of Colombia, Brazil, Venezuela and Panama.
How do you watch an eclipse safely?
Whatever you do, do not look directly at the sun during a partial or total solar eclipse.
If you’re planning on seeing the eclipse in-person, make sure to use proper eye protection. You’ll need special eclipse glasses or a pinhole camera.
In a pinch, you can also make a make a pinhole camera by making a tight circle with your fist. Then look for the shadow of the crescent sun on the ground. The gaps between the tree leaves can serve the same purpose, projecting hundreds of tiny, flickering images of the sun.
You can watch the eclipse online, too.
If you’re not already in or near one of the South American cities in the path of the eclipse, there are plenty of places to watch it online:
The European Southern Observatory, which runs La Silla, started livestreaming the eclipse around 3:15 p.m., about an hour before totality. Or you can watch it in the video player embedded above.
The Slooh Community Observatory will have broadcasts from telescopes locations in Chile and Argentina.
And you can catch also TimeandDate.com’s eclipse coverage on YouTube.
When is the next solar eclipse?
If you miss the solar eclipse, or are so transformed by viewing it that you want to chase the next one, don’t worry. Total solar eclipses happen somewhere around the world every 18 months or so.
The next one will happen as soon as December 2020. It will pass over Chile and Argentina again, as well as parts of southwest Africa and Antarctica. And the next one over the United States will be in 2024, blazing a northeast-bound path that starts in Mexico in the southwest and crosses the entire United States until it ends in Canada.