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Two summers ago, on August 21, 2017, thousands of people from across the world witnessed the "Great American Solar Eclipse," the first total solar eclipse to occur exclusively over the continental United States since January 11, 1880. Now, stargazers are getting excited to watch the Sun disappear again for a brief period on July 2, 2019 — this time, the eclipse's narrow path will extend across the South Pacific all the way to Chile and Argentina.
The "Great South American Eclipse" is particularly thrilling for astronomy fans because two world-class observatories — the Cerro Tololo Inter-American Observatory and the La Silla Observatory — lie directly in the path of totality. The powerful telescopes, positioned in Chile's remote areas known for their clear skies, will capture the stunning phenomenon live and broadcast it to hundreds of countries and millions of people worldwide. Meanwhile, over 400,000 "eclipse chasers" plan to descend to Chile's Coquimbo region, which lies in the path of totality, to watch the wondrous spectacle in person.
The maximum totality of the eclipse — the largest amount of time the moon will cover the Sun — is expected to be four minutes and thirty seconds, or about 70 percent longer than the 2017 Great American Eclipse, which lasted 2 minutes and 40 seconds. However, because the eclipse is set to begin while the Sun and moon are angled over the Pacific Ocean, only observers on a few boats and airplanes will get to experience the full duration. Those watching the celestial event on land, in Chile and Argentina, will have to be satisfied with just two minutes and thirty-five seconds of darkness.
Fleeting as they are, total solar eclipses allow scientists an opportunity to investigate mysteries such as why the sun is so hot, or what causes the unpredictable, and often dangerous, solar flares that emanate from its surface.
A solar eclipse occurs when the Earth, moon, and Sun align with the moon in the middle. However, we do not experience a total solar eclipse every time this happens because the moon’s elliptical orbit causes its distance from Earth to vary between 221,500 miles to 252,000 miles. For a total solar eclipse to occur, the moon has to be at its closest orbital distance — so it appears bigger than the star — and in perfect line with the Earth and the Sun.
Total solar eclipses, which occur about every 18 months, are not rare events. However, what makes watching the Sun's brief disappearance so exciting is that it is only visible to those directly in the path of the moon's umbra, the darkest part of the shadow from inside which the entire disk of the Sun is obscured. Since this typically measures between just 93 miles (150 kilometers) and 155 miles (250 kilometers) across, only a small percentage of the Earth's sunlit hemisphere is able to enjoy the experience live. Moreover, total solar eclipses occur at a specific location, on average, every 360 years, which makes watching one in real time a genuinely once-in-a-lifetime opportunity.
If you are among the lucky few in the path of this summer's "Great South American Eclipse," be sure to wear special glasses to protect your eyes from the Sun's harmful infrared and ultraviolet radiation, which can result in permanent damage or even blindness. Those not in the path of the solar eclipse will be pleased to know that due to the moon's orbit, the event is usually followed by a more widely visible lunar eclipse. On July 16 and July 17, 2019, a large part of the world, including South America, Europe, Africa, Asia, and Australia, will be treated to a spectacular partial "blood moon," or lunar eclipse.
Resources: astronomy.com,space.com,whenisthenexteclipse.com, wikipedia.org