Monday, August 14, 2017

Dark Days Ahead: The Great American Eclipse, Part II

Are you ready? We* are just one week away from a total solar eclipse, an event NASA calls “one of nature’s most awe inspiring sights.” Considering all of the inspiring sights NASA has unveiled over the years, that’s saying a lot! The total solar eclipse will be visible from a narrow band of the United States stretching from coast to coast on August 21. Weather permitting, everyone in the United States (including Hawaii and Alaska) along with people in regions of South America, Africa, and Europe will have the opportunity to see at a least partial solar eclipse. For more on logistics and geography, check out The Great American Eclipse, Part I.

A TOTAL solar eclipse is about as bright as the full Moon—and just as safe to look at. But the Sun at any other time is dangerously bright; view it only through special-purpose “eclipse glasses” or hand-held solar viewers that meet the ISO 12312-2 international standard for such products. Homemade filters or ordinary sunglasses, even very dark ones, are not safe for looking at the uneclipsed or partially eclipsed Sun.
Image Credit: Courtesy Mark Margolis / Rainbow Symphony.

If you aren’t already prepared, it’s time to get ready; you don’t want to miss this. Take two simple steps to make the most of your viewing:

1.  Figure out when the eclipse will be visible in your area. You can do this by visiting one of the websites below. Note that there are four key pieces of information: the maximum portion of the sun that will be eclipsed by the moon as visible from that location, the time at which the maximum occurs (often called the “peak” time), the eclipse start time, and the end time. From start to finish, the eclipse will happen over about 90 minutes. You’ll want to look up at peak time for sure, but try to check in at a few other times as well.
  • Vox – This user-friendly page provides information on what you’ll be able to see based on your zip code.
  • Space.com – On this page you can put in your exact addresses and get the details in local time.
  • NASA has an interactive eclipse map that lets you click on your city and get the details for that location. Note that the time is given in UT, universal time. Below the map is a table that shows how to convert UT to your time zone. 
If you want to see the total solar eclipse, you need to be in the path of totality. This will take more planning—hotel rooms are completely booked in many cities along the path, and traffic is expected to be intense. It’s going to be amazing so don’t let this discourage you, but do make a plan.

2.  Protect your eyes. You don’t want to miss the eclipse, but you also don’t want to damage your eyes. Do not, I repeat, DO NOT look at the sun during an eclipse without appropriate eye protection. You wouldn’t stare at the sun normally, even with sunglasses, so don’t do it during the eclipse. You need certified glasses approved for eclipse viewing. There are companies selling unsafe “eclipse” glasses so be careful! To avoid eye damage, read this guide to safe eclipse eyewear and this guide to reputable vendors by the American Astronomical Society before you purchase eclipse glasses or look through a telescope. Also, if you plan to use a camera to photograph the eclipse, use a filter, or you risk damaging your equipment permanently. There is one exception to these rules: people in the path of totality can safely look at and photograph the total solar eclipse without protection only during the 2-2.6 minutes of totality.

Can’t get your hands on a pair of safe eclipse glasses? No problem!

  • Search for local events on this NASA page as well as in local publications. Many schools, libraries, astronomy clubs, and science centers are holding events featuring all kinds of eclipse viewing opportunities.
  • Create a pinhole projection—its quick, easy, and safe, and teaches a bit about optics! You can even use a colander.
  • Check out NASA’s Television’s four-hour coverage, Eclipse Across America, which will be live streamed. 

Many people are scrambling to get eclipse-ready at the last minute, but scientists have been preparing for this eclipse for YEARS. The eclipse provides many unique opportunities to learn about the sun, Earth, moon, and space. For example…

A total solar eclipse is the ideal time to study the sun’s mysterious corona, the intensely hot halo that surrounds the sun. While the surface of the sun is only about 6,000°C, the corona is somewhere in the neighborhood of 1,000,000°C. Usually, the corona's light is washed out by light from the surface of the sun, but when the moon blocks the disc of the sun and the sky goes dark, the structure of the halo becomes visible. Scientists are thrilled at this chance to study what makes the corona so much hotter than the surface of the sun and investigate its influence on the Earth. There are other techniques for observing the sun’s corona, but none are as good as a total solar eclipse!

The total phase of the March 20, 2015, solar eclipse as seen from the Svalbard archipelago in the Arctic. This is a composite of short, medium, and long exposures, as no single exposure can capture the huge range of brightness exhibited by the solar corona. The longest exposure in the composite captured the faint illumination of the Moon by earthshine, that is, sunlight reflected off the Earth. No filter was used during the exposures, as totality is about as bright as the full Moon and just as safe to look at. At all other times, though, a safe solar filter is required to observe or photograph the Sun.
Image Credit: Reinhard Wittich.

Scientists from the Harvard-Smithsonian Center for Astrophysics will study the corona in infrared light from an aircraft flying high above Kentucky during totality, in hopes of finding out more about its magnetic field. The Southwest Research Institute is leading a team that will also be flying during the eclipse, onboard NASA research aircrafts. This team will focus on observing the motion of the corona in visible and infrared light. Strategically located instruments will be observing the sun’s corona from the ground. For more on these research efforts, check out this recent story in Scientific American.

Several scientists are taking this opportunity to explore how the sun’s radiation affects the Earth’s atmosphere. Instruments on the ground will study the amount and type of radiation reaching the earth during totality, while at the same time instruments in space will study the radiation reflected outward by the earth.

In addition to using instruments based on the ground, in space, and on airplanes, scientists will be launching high altitude balloons during the eclipse. These balloons will take data on the Earth’s atmosphere, cosmic rays, and other aspects of nature influenced by the eclipse. Student groups will launch 55 balloons along the path of totality that will livestream footage to the NASA website. Some of these balloons will carry bacteria strains in a test of how well the strains handle the Mars-like conditions of the Earth’s stratosphere that occur during an eclipse.

A number of groups also have citizen science projects tied to the eclipse, where viewers like you and I can take and submit photographs, videos, or measurements during the eclipse. If enough viewers take part in these projects, scientists end up with a significant number of data points collected from a wide variety of locations. Combined, this information can lead to meaningful discoveries. For a list of such projects, visit the Citizen Science page of NASA’s eclipse website—and check back this Wednesday for part III of our eclipse coverage, including an exciting look at one of these projects.

Wherever you’ll be during this eclipse, Physics Buzz wishes you clear skies and safe viewing!

Kendra Redmond


*We know many Physics Buzz readers don’t live near the viewing area of this eclipse. If you are one of them, check out Time and Date’s list of upcoming eclipses to see if there is one coming soon to your area. We are especially excited about the August 21 eclipse since the path of totality is within driving distance of the PhysicsCentral office. If you’re out of range, check out NASA’s livestream of the event, Eclipse Across America.

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