Total Solar Eclipse 2017: Here's What the Sun's Corona Will Look Like to Scientists

The total solar eclipse on August 21 will be a historic occasion for everyone in the United States. But for scientists observing the totality, it will be extra special.

Astronomers observing the eclipse along the path of the totality—a roughly 70-mile-wide path stretching from Oregon in the northwest to South Carolina in the southeast—will be able to see the corona, the wispy, glowing atmosphere that surrounds the Sun.

The National Solar Observatory has produced a detailed image of what the corona will look like on August 21. Streams of light protruding from the Sun’s north and south pole will be visible, as well as concentrated bubbles of light close to the surface—although to our eyes, it will like just look like a “fuzzy halo” around the Sun, according to Dr. Gordon Petrie from the NSO.

Total solar eclipse corona This National Solar Observatory image shows a model of the sun's corona during the August 21 total solar eclipse, based on measurements taken one solar rotation (or 27.2753 Earth days) before the event. National Solar Observatory

The light from the corona, a plasma aura that surrounds the Sun and other stars, is usually overwhelmed by the Sun’s radiance. But during the total solar eclipse, the moon blocks out the Sun’s direct light, leaving the star’s outer atmosphere visible.

The light streaming out from the Sun’s poles are known as polar plumes, while the bright bulbs of light close to the Sun’s surface are called helmet streamers. The latter form when magnetic field lines from the Sun loop back on themselves, trapping the coronal plasma.

Read more: A total solar eclipse passes through 10 states on August 21. Here's when to watch it

The Sun has its own magnetic field that is rooted deep within the star. The patterns produced by its magnetic field are measured using superheated gases in the Sun’s atmosphere to trace out the lines. Petrie compared this process to “sprinkling iron filings over a bar magnet to get a butterfly shape.”

Scientists were able to predict the shape of the corona on July 25, which constitutes one complete solar rotation—equivalent to about 27 Earth days—prior to August 21. “The corona is not likely to change too much between now and the eclipse, unless we get lucky and a large active region appears,” said Petrie.

The corona will be visible for a total of 90 minutes during the August 21 eclipse, much longer than usual. For scientists, the total solar eclipse will offer a rare opportunity to study the corona. "At a total solar eclipse, scientists collect important and unique information about how this major layer of the solar atmosphere functions, and how it changes over the 11-year solar cycle," Jay Pasachoff, Field Memorial Professor of Astronomy at Williams College, told Newsweek in July.

Skywatchers elsewhere in the United States will still witness a partial solar eclipse. Anyone watching the eclipse, which will pass through 14 states, is advised to follow NASA guidelines including wearing safety glasses equipped with solar filters to avoid sustaining damage to their eyes during the event.

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