What were those red spots during the solar eclipse? An astronomer explains

As skies darkened Monday over North America during a rare solar eclipse, many people noticed bright dots — flickering spots that were reddish, pink and orange in hue — along the periphery of the moon and Sun.

Those brilliant red spots, say experts, are called solar prominences. Here's what that means.

What are solar prominences?

Solar prominences, explains NASA, are large, bright loops of plasma anchored to the Sun's surface in the photosphere — the visible surface of the Sun — that extend into the Sun's outer atmosphere. These prominences are sometimes visible during a solar eclipse.

"They're sort of like an appendage coming out of the chromosphere of the Sun," said Butler University Physics & Astronomy professor Brian Murphy. "That red color people noticed is fluorescing hydrogen gas, just in the right temperature and density to give us this pinkish color."

Experts say you can think of solar prominences as being akin to the clouds in Earth's atmosphere, but instead of suspended water vapor, these giant tendrils of hot gas are trapped by magnetic fields. They can reach distances of 93,000 miles above the Sun's surface and last for several months, according to NASA, unless they erupt.

As a solar prominence flows along a tangled and twisted structure of magnetic fields, says NASA, they either collapse back into the Sun's surface or can become unstable, break and burst outward, releasing the plasma in a dazzling display of energy.

Was that a solar flare during the eclipse?

Many photos Monday managed to catch a bright spot at the bottom of the eclipse. Murphy explained people were probably witnessing a "post eruptive solar prominence," which was likely the location of a solar flare.

When a solar prominence is 'post eruptive'

"Think of a rubber band stretched in the shape of a horseshoe magnet," Murphy said. "Now imagine that rubber band breaking at the top. That's when you get material ejected quite often from the sun or a solar flare, when the magnetic field is reconnecting — that's what we mean by 'post eruptive'."

What is a solar flare?

A solar flare is an intense burst of radiation near a sunspot that releases magnetic energy out into space, according to NASA. These giant explosions from the sun send energy, light, and particles throughout the solar system. Flares can last several minutes to several hours. Sometimes this burst of energy can cause geomagnetic storms on Earth.

What's the difference between a solar flare and a coronal mass ejection?

While coronal mass ejections (CMEs) and solar flares are both tremendous explosions of energy that occur on the Sun, they move at different speeds.

Solar flares, NASA says, are some of the most powerful explosions in the solar system. Particles from a solar flare can travel at the speed of light and reach Earth in minutes. CMEs, explains NASA, are large clouds of solar plasma and magnetic fields from the Sun that can take up to three days to reach our planet.

Credits: NASA’s Goddard Space Flight Center/Mary Pat Hrybyk-Keith

Community science groups across U.S. capture video of 2024 solar eclipse

Murphy said community science groups at 35 telescope stations across the country collaborated Monday to capture video clips of the total eclipse as it stretched from Texas to New England.

These 2-3 minute clips, as part of a National Science Foundation project, will later all be combined into a 60-minute video to help study the Sun's corona. Speaking on behalf of the Citizen Continental-America Telescope Eclipse (Citizen CATE) 2024 project, Murphy said he and others were excited to see the solar prominence — those red dots — in their recordings.

"It was pretty obvious to the eye as well," he said, "which made it even better."

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John Tufts covers trending news for the Indianapolis Star. Send him a news tip at JTufts@Gannett.com. Follow him on X at @JTuftsReports.