Everything You Need to Know About the Aug. 21 Eclipse
On Aug. 21, all of North America will experience a solar eclipse.
If skies are clear, eclipse-watchers will be able to see a partial solar eclipse over several hours, and some people â within the narrow path of totality â will see a total solar eclipse for a few moments.
Itâs never safe to look at the Sun, and an eclipse is no exception. During a partial eclipse (or on any regular day) you must use special solar filters or an indirect viewing method to watch the Sun.
If you have solar viewing glasses, check to make sure theyâre safe and undamaged before using them to look at the Sun. Make sure you put them on before looking up at the Sun, and look away before removing them. Eclipse glasses can be used over your regular eyeglasses, but they should never be used when looking through telescopes, binoculars, camera viewfinders, or any other optical device.
If you donât have eclipse glasses, you can still watch the eclipse indirectly! You can make a pinhole projector out of a box, or use any other object with tiny holes â like a piece of cardstock with a hole, or your outstretched, interlaced fingers â to project an image of the partially eclipsed Sun onto the ground.
Of course, if itâs cloudy (or youâd just rather stay inside), you can watch the whole thing online with us at nasa.gov/eclipselive. Tune in starting at noon ET.
If youâre in the path of totality, there will be a few brief moments when it is safe to look directly at the eclipse. Only once the Moon has completely covered the Sun and there is no light shining through is it safe to look at the eclipse. Make sure you put your eclipse glasses back on or return to indirect viewing before the first flash of sunlight appears around the Moonâs edge.
A solar eclipse happens when the Moon passes directly between the Sun and Earth, casting its shadow down on Earthâs surface. The path of totality â where the Moon completely covers the Sun â is traced out by the Moonâs inner shadow, the umbra. People within the Moonâs outer shadow, the penumbra, can see a partial eclipse.
The Moonâs orbit around Earth is tilted by about five degrees, meaning that its shadow usually doesnât fall on Earth. Only when the Moon lines up exactly between the Sun and Earth do we see an eclipse.
Though the Sun is about 400 times wider than the Moon, it is also about 400 times farther away, making their apparent sizes match up almost exactly. This is what allows the Moon to block out the Sunâs bright face, while revealing the comparatively faint, pearly-white corona.
Eclipses are a beautiful sight to see, and theyâre also helpful for our scientists, so weâre funding eleven ground-based science investigations to learn more about the Sun and Earth.
Total solar eclipses reveal the innermost regions of the Sunâs atmosphere, the corona. Though itâs thought to house the processes that kick-start much of the space weather that can influence Earth, as well as heating the whole corona to extraordinarily high temperatures, we canât study this region at any other time. This is because coronagraphs â the instruments we use to study the Sunâs atmosphere by creating artificial eclipses â must cover up much of the corona, as well as the Sunâs face in order to produce clear images.
Eclipses also give us the chance to study Earthâs atmosphere under uncommon conditions: the sudden loss of solar radiation from within the Moonâs shadow. Weâll be studying the responses of both Earthâs ionosphere â the region of charged particles in the upper atmosphere â and the lower atmosphere.
Learn all about the Aug. 21 eclipse at eclipse2017.nasa.gov, and follow @NASASun on Twitter and NASA Sun Science on Facebook for more. Watch the eclipse through the eyes of NASA at nasa.gov/eclipselive starting at 12 PM ET on Aug. 21.Â
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
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