On August 21, a solar eclipse will be viewable throughout the United States for the first time in 99 years. For those in its path of totality, daylight will completely disappear for a few minutes. What is the path of totality? And why is this one of the most exciting celestial events of the century? Here, NASA’s lead scientist for Eclipse 2017, Madhulika Guhathakurta, answers our burning questions.
“I was born to be a space cadet,” Guhathakurta says with a laugh, explaining that her birthday happens to be the same day that Sputnik launched. Scroll down for Guhathakurta’s guide to the eclipse (including important safety precautions)—plus the best getaways in the path of totality!
What is a total solar eclipse?
A total solar eclipse is when the moon comes in between the sun and Earth, and from a vantage point on Earth, allowing for the shadow of the moon to completely cover the yellow disc of the sun.
What will this total solar eclipse look like to us, here on Earth?
If you happen to be on the right spot where this umbral shadow falls on our planet—[also known as] the path of totality—you will be able to see the total solar eclipse. During totality, for a few minutes, there will be complete darkness. It will get dark, kind of like twilight, it will get cold, you will actually see stars and planets come out that we normally don't see during daylight. Animals big and small sense the change in light and air temperature and take on their nocturnal behavior.
When the visible disc of the sun is completely covered, and you see darkness in its place, you see this beautiful, [crown-like] structure [around the blocked-out sun] called the corona. The only time you can see the corona with unaided eyes is during a total solar eclipse. The halo of the corona is about the same brightness as a full moon. If you have a second to look away at the horizon, it will be a 360-degree sunset.
The path of totality is a narrow band, about 70 miles wide, diagonally crisscrossing from the coast of Oregon all the way to Charleston, South Carolina. If you go to the NASA website, you can enter your location, and it will tell you what phase of the eclipse you will be watching and at what time.
If you're not in the path of totality, what you'll see are partial phases of the eclipse, which are crescent suns, similar shapes as that of a crescent moon. There will be various degrees of partial phases through the entire US, and this is an eclipse that will be visible everywhere in the US including Hawaii and Alaska. I don’t think people are going to feel the ambient light change much unless the partial eclipse is at least 90 percent or more. But if they were to look at the sun with appropriate eclipse glasses, they will absolutely see the progression of the eclipse and crescent sun. It’s a fascinating, magical moment.
Why do total solar eclipses occur?
Because of two coincidences: The sun is 400 times wider than the moon. The sun is also 400 times farther away from our Earth than the moon is. Therefore, when we look at the sun and the moon in the sky, they appear to us to be the same size. Additionally, the plane along which the Earth goes around the sun, called the ecliptic plane, and the plane along which the moon goes around the Earth are slightly off angle, about .5 degrees. Solar eclipses occur during the new moon and when these planes coincide.
This cosmic coincidence and planar geometry blocks the visible disc of the sun completely. You have to completely cover the yellow ball of the sun—even if there is one ray of sun passing through the moon’s mountains, craters, and valleys, you will not have a total solar eclipse.
Are total solar eclipses uncommon?
No. They happens about every 12-18 months on different parts of the Earth, most of them remote, inaccessible, and over oceans because Earth is over 70 percent water. However, at a given place on Earth, total solar eclipses occur very rarely, about once every 400 years. Last time I watched a solar eclipse was in Indonesia in March 2016. I only caught a few glimpses as it was cloudy and rainy in the area when our telescopes were set up.
Why is this one so special?
What makes this one unique is the time it is happening and the path it is covering. The last time a total solar eclipse crisscrossed the entire continent of the US was 99 years ago in 1918. There is no one alive who remembers the last transcontinental American eclipse. The vast majority of Americans have never seen or even heard of a total eclipse of the sun. This eclipse provides an opportunity for every American to participate in it. The eclipse is coming to you. That's why this one is called the All-American Eclipse. We are going to be covering this eclipse like no other eclipse has been covered. From NASA, we have all our spacecraft lined up to observe this eclipse both along and away from the path of totality. We have balloons, airplanes, and ground-based instruments all along the path of totality. Balloons will be launched by undergraduate students all along the path of totality. Google will be partnering with the Mystery Science journal, for everyone to document their interaction with the eclipse. This is, in a way, going to be the most observed, photographed, and appreciated eclipse in the history of eclipses.
What safety precautions should eclipse viewers take?
You cannot look at the sun directly without aid, without appropriate eclipse glasses. There are particular filters [see NASA’s eyewear recommendations here]. That is the most important aspect of the eclipse because a partial solar eclipse is going to be seen by everybody in every state in America. The only time, and I repeat, the only time, you can look at the sun directly without eclipse glasses is during the phase of the totality, when the entire visible disc of the sun is blocked, we descend into this deep blackness of the visible photosphere, and out comes this pearly halo, a shimmering corona. If you have your glasses on during totality, you will miss the whole show. You will not see the corona.
Is a total solar eclipse an opportunity for NASA to make scientific discoveries?
Absolutely. The corona is the start of the outer atmosphere of the sun. Only during a total solar eclipse can we can see the very inner edges of the corona in visible light. This is the only time when we can try out new instruments to observe the corona in higher spatial, temporal and spectral resolutions than done before. These new measurements have the potential for new discoveries.
During a total eclipse, the lower parts of the sun's atmosphere, or corona, can be seen in a way that cannot completely be replicated by current human-made instruments. The lower part of the corona is key to understanding many processes on the sun, including why the sun’s atmosphere is so much hotter than its surface, as well as the process by which the sun accelerates solar wind and sends out a constant stream of particles and radiation, produces solar storms which propagate through the corona, all of which can cause changes in the nature of space and impact spacecraft, communications systems, and orbiting astronauts.
Since a total solar eclipse shuts off the sunlight, can it cause a power outage?
It’s expected that there will be a dip in the power—though it’s not a bigger dip than a regular night. Think of California. A big fraction of its power comes from solar energy. If you're cutting off the visible disc of the sun, you're actually cutting out that energy input to solar-powered grids. The totality is very short, but the entire phase of the eclipse is a few hours from beginning to end. So there’s going to be less power generated from solar-powered grid.
WANT TO SEE THE SOLAR ECLIPSE IN ALL OF ITS GLORY? ESCAPE TO ONE OF THESE GETAWAYS IN THE PATH OF TOTALITY!
1) Brooks Winery, Amity, Oregon
My name is: Abby McManigle, Executive Chef at Brooks Winery in Amity, Oregon.
This place is special because:we have the most expansive Riesling portfolio in Oregon. We also have a full-service kitchen and culinary events with a strong emphasis on food and wine pairings.
This is the perfect spot to view the eclipse from because: We will turn the winery into an overnight camp site the night before the eclipse, on Sunday, August 20th. In addition to the wines and tents that we are providing, we are also having a BBQ dinner with live music the night before as well as an eclipse talk and star watch with Professor Siegel, an astrophysicist from Lewis & Clark College. Plus outdoor yoga and breakfast the day of the eclipse and a pizza lunch from our wood-fired oven.
While you’re in the neighborhood, you must try: Oregon has some of the best outdoor activities in the country. Hiking, biking, canoeing, the coast lines, etc. Unplug and explore it!
I will be celebrating the eclipse by: cooking our Champagne Brunch in the morning, celebrating the release of our very first Brooks Estate Sparkling Riesling.
2) InvitedHome’s Grand Outlook in Jackson Hole, WY
My name is: Will Farrow, Director of Operations for InvitedHome in Jackson Hole, WY
This place is special because: Jackson Hole is bordered on the west by one of the most rugged and dramatic mountain ranges in the world—the Tetons. People come from around the world to visit Grand Teton National Park and Yellowstone National Park just north of here. Wildlife viewing, natural scenery, hiking, fishing, mountain biking, rafting, and climbing are all widely known to be exceptional, and Jackson Hole Mountain Resort is on any serious skier or snowboarder's bucket list.
Sitting on a secluded five acres on the sought-after East Gros Ventre Butte, our modern Grand Outlook home offers world-class amenities but with the level of privacy only a home can afford. Inside is an exercise room, sauna, spacious outdoor area with hot tub, and five bedrooms with 6.5 bathrooms.
This is the perfect spot to view the eclipse from because: The dramatic scenery of the Tetons and the Snake River Valley (aka Jackson Hole) are breathtaking on their own. Adding a celestial event like a total eclipse will create a unique and spectacular experience as well as memories to last a lifetime. The home’s location and lack of neighbors means that guests will have the most unbeatable views of the eclipse in the country, while relaxing in the hot tub or sitting on the patio with friends and loved ones.
I will be celebrating the eclipse by: embarking on an early a.m. hike to the remote summit of a nearby mountain where I can watch the moon's shadow cross those Tetons.
3) Salishan Spa in Gleneden Beach, OR
My name is: Steven Hurst, general manager of Salishan Spa and Golf Resort.
This is the perfect spot to view the eclipse from because: Salishan is located along the central Oregon coast, where the eclipse will first make landfall, so people visiting our resort will be among the first in North America to witness the phenomenon. We have opened up the event lawn to our resort guests so they can experience the true magic of nature for themselves. We are providing guests with complimentary viewing glasses, and breakfast will be available in the nearby Sun Room or a buffet breakfast and lunch also are available. The property also has created a special Coastal Eclipse cocktail.
This experience is special because: The eclipse happens in the morning, so guests will have a full day to enjoy the amenities at Salishan, from our championship 18-hole golf course to a relaxing visit to the spa.
I will be celebrating the eclipse by: hosting hundreds of people for a one-in-a-lifetime experience at Salishan.