May 18, 2012
On Sunday evening, for the first time in 18 years, a solar eclipse will be visible from the continental United States. This won’t be your typical eclipse, either—as in the picture above, from October 3, 2005, the moon will cross directly in front of the sun but block out only a portion of its light, leaving a “ring of fire” that is much thicker than the ring seen during most total eclipses.
Why the ring of fire? Total solar eclipses occur when the moon passes directly between the sun and earth, covering up the sun for a brief duration from our vantage point. Because the moon is currently near apogee—meaning it’s at a point in its orbit that is farther from us than usual—the moon appears smaller in the sky, and thus isn’t large enough to block the entire sun. The result: a bold, shimmering ring of fire, known as an annular eclipse.
Unfortunately, those on the East Coast (including us here at Smithsonian) won’t be able to see the eclipse at all, since the sun will set by the time it will occur. Many residents of Western states will be able to see the ring of fire eclipse during the afternoon or evening on Sunday; others will see a partial eclipse, in which the moon crosses in front of the sun off-center, blocking just one portion of it. This NASA map shows the thin swath of the United States that will be able to see the annular eclipse. If you’re outside it, you can click on your exact location to see what time you should look to the sky to see a partial eclipse.
Although up to 94 percent of the sun’s light will be blocked out by the eclipse, looking at it for even a few seconds with the naked eye can cause permanent harm to your retinas. (Don’t try watching with your smartphone or digital camera, either—it can damage the lens.) Instead, punch a small hole in a piece of cardboard and allow the sun’s light to pass through it, and you’ll see a projected image of the eclipse on the ground. You can also look to the shaded ground beneath a leafy tree to see the shadows turn into circular rings of light.
Watch the video below by Science@NASA for a full explanation of the astronomical phenomenon:
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