Two years from today: get ready for the Great American Solar Eclipse of 2017

A total eclipse of the Sun, showing the Sun’s atmosphere, or corona, stretching out into space, which is not normally visible during daylight. Photo Credit: Fred Espenak/NASA’s Goddard Space Flight Center
A total eclipse of the Sun, showing the Sun’s atmosphere, or corona, stretching out into space, which is not normally visible during daylight. Photo Credit: Fred Espenak/NASA’s Goddard Space Flight Center

Exactly two years from today, on Aug. 21, 2017, a rare total solar eclipse will be seen again in the skies of the United States, racing east from Oregon to South Carolina. For a brief couple of minutes, the skies will darken as the Moon passes in front of the Sun, revealing the Sun’s corona, which is not normally visible in daylight, to millions of people as it crosses coast to coast for the first time in nearly a century. A total solar eclipse is one of the greatest sights in nature, not to be missed, and many are already making plans to witness the event.

During the moment of totality, the Earth, Moon, and Sun are lined up in a rare perfect alignment, and by cosmic coincidence the Moon and Sun appear to be exactly the same size. When the Sun’s disk is blocked by the Moon, the Sun’s atmosphere, or corona, becomes visible, looking like a bright ring of light around the dark disk of the Moon. The spectacle can be an emotional one as one watches this beautiful but fleeting natural phenomenon.

Path of the 2017 total solar eclipse. Credit: Michael Zeiler/
Path of the 2017 total solar eclipse. Image Credit: Michael Zeiler/

These eclipses are possible because, while the Sun is about 400 times larger in diameter than the Moon, the Moon is also about 400 times closer to the Earth than the Sun, so that the Sun and Moon appear to be almost exactly the same size in the sky. It was different when the Moon first formed a few billion years ago, when it was closer to the Earth and so appeared larger. But due to friction from tides, the Moon has been gradually receding from Earth since then.

“I well remember the last total solar eclipse that passed through my home state of SC in March of 1970, I was 12 years old at the time and lived directly in the path of totality,” said Hap Griffin, an accomplished astrophotographer of nearly three decades who owns his own observatory and a business that modifies DSLR cameras for better astronomical performance. “I’ve waited 45 years for another one and am completely excited that the eclipse of 2017 will again pass directly over my home area. I am working with my local astronomy club to prepare a pool of public speakers and presentations so that we can alert the public to the event coming up in only two years!”

Travel agencies, national parks, and other organizations are already making plans (or selling tickets) to witness the eclipse, and many communities on the eclipse center line across the country are developing their own logistical plans to support the large crowds expected. Some of the larger and more well known places in the path of the eclipse include Salem, Ore.; Grand Teton National Park, Wyo.; St. Louis and Kansas City, Mo.; Nashville and Great Smoky Mountains National Park, Tenn.; and Charleston, S.C. The small Kentucky town of Hopkinsville, however, is nearest the point where the eclipse totality will last the longest: 2 minutes and 40 seconds.

For the total solar eclipse in 2017, maps of the best locations to view it can be seen here. The eclipse totality will only be visible from locations within the yellow path. The green lines are the times of greatest eclipse and the orange curves inside the path of the eclipse show the duration of the eclipse. The time above the path of totality is Universal Time (formerly Greenwich Mean Time) and the time below is the local time zone.

There is also a larger and very cool map which can be downloaded, showing the path of totality across the United States on the day of the eclipse. After downloading, scroll across to see the path from the west coast to the east coast. If you were to print the map, it would be 8 inches tall by 10 feet, 8 inches long! The map includes oval figures for the shadow of the Moon, drawn at three-minute intervals and at local times. There is also a short description of the area and the speed of the Moon’s shadow as it progresses.

A total solar eclipse over Svalbard, Norway. Photo Credit: Thanakrit Santikunaporn
A total solar eclipse over Svalbard, Norway. Photo Credit: Thanakrit Santikunaporn

Bottom line: The closer you are to the center of the path, the longer the duration of the eclipse. Other topics related to the eclipse are also included on the map, and a desktop background for your computer (Mac or PC) is available showing the entire eclipse path.

Some solar eclipses are called annular solar eclipses, when the disk of the Moon doesn’t quite cover all of the Sun’s disk. The apparent sizes of the Moon and Sun can vary slightly due to the Moon being in a slightly elliptical orbit around the Earth and the Earth revolving in a slightly elliptical orbit around the Sun. The sky doesn’t get quite as dark as it does during a total solar eclipse, but is still a beautiful sight. The next annular solar eclipse to be seen from the United States will be Oct. 14, 2023. If the Moon’s shadow isn’t centered on the Earth, then a partial solar eclipse will occur, and only part of the Sun is blocked out by the Moon. The last partial solar eclipse in the United States was Oct. 23, 2014.

Solar eclipses don’t occur every month, since the orbit of the Moon has a tilt of about 5 degrees with respect to the Earth’s orbit around the Sun. A solar eclipse would only happen every month if the orbit of the Moon was exactly within the same plane as the orbit of the Earth around the Sun.

An airliner passing through the crescent eclipsed sun. Photo Credit: Mike Killian
An airliner passing through the crescent eclipsed sun. Photo Credit: Mike Killian

The total solar eclipse of 1918 also crossed the United States in a path similar to the upcoming one in 2017, from Washington state to Florida. That was the last time a total solar eclipse crossed the country from one coast to the other. A good summary of historical solar eclipses is here.

More information about the 2017 total solar eclipse is available on the Great American Eclipse website, including a blog to help keep you updated as the time approaches. And remember, don’t watch a solar eclipse without proper solar filters when any part of the Sun itself is still visible. More information about eye safety is here and here.

“There are precious few events in life that leave such an indelible impression that the simple act of recollection can quicken the pulse and increase respiration as vivid memories flood one’s mind. The total eclipse of the Sun is just such an event.

“The simple act of standing within the shadow of the Moon affords the rare and unprecedented opportunity to gaze directly at the halo of million-degree plasma surrounding our star. Twisted, tortured, and constrained by the Sun’s enormous magnetic fields, the solar corona is revealed to the naked eye only during the brief seconds when the Moon complete blocks the brilliant disk of the Sun.

“The corona’s gossamer crown of pearly light displays an ethereal beauty that transcends both science and nature. It hypnotizes the viewer into an altered state where time seems to stand still. Nevertheless the diamond ring of third contact, signaling the end of totality, appears much too quickly. Hungry eyes search in vain for one last glimpse of the corona hidden by the rapidly expanding glare.

“Totality is over. The memory of this fleeting event will be replayed many times in the years to come. But for some people it will not be enough. They will travel to the far corners of the globe at the appointed time and place to witness the grand spectacle again. And again. And again. They are the eclipse chasers.”

— From the book “Total Addiction” by Kate Russo.

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This article was first published on AmericaSpace.

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