What’s up with that huge dark hole in the Sun?

By Tom Yulsman | July 11, 2016 10:48 am

Not to worry, everything’s under control

An animation of images of the Sun acquired by NASA's Solar Dynamics Observatory spacecraft on July 11, 2016 highlights a dark area covering the top of the Sun known as a "coronal hole." (Source: NASA Solar Dynamics Observatory)

An animation of images of the Sun acquired by NASA’s Solar Dynamics Observatory spacecraft on July 11, 2016 highlights a dark area, called a “coronal hole,” covering the top of the Sun. In the animation, the Sun is seen in extreme ultraviolet light. This highlights the atmosphere —the Sun’s corona. Hot, active regions are bright. The dark coronal hole is an area where very little radiation is being emitted. (Source: NASA Solar Dynamics Observatory)

Every once in awhile, the Sun develops a huge “hole” — a dark patch in its outer atmosphere, or corona, like the one visible above.

This is the Sun, as seen today by NASA’s Solar Dynamics Observatory.

I’ve posted about these coronal holes before, but I really like this animation, as well as the one below offering a visualization of what’s actually going on.

SEE ALSO: The Sun blows its top — again 

A coronal hole is a place where where the Sun’s magnetic field opens out into interplanetary space, allowing hot material from the corona to speed outward. As a result, these areas have very little hot plasma compared to their hotter, brighter surroundings. So they appear much darker.

Solar coronal hole and magnetic field lines

This video clip shows the Sun as seen by the Solar Dynamics Observatory spacecraft on June16, 2016. A map of the Sun’s magnetic field is overlaid on the SDO video.

In the animation above, acquired by the SDO spacecraft on June 16th, the Sun is once again seen in extreme ultraviolet light, highlighting the corona. A coronal hole is evident here too. This animation also adds a map of the Sun’s magnetic field lines.

Those lines are tightly bundled near the brighter active regions in the corona. Here, the Sun’s magnetic field is particularly intense. Meanwhile, the magnetic lines from the coronal hole clearly open out into space, allowing hot particles to stream outward.

The result: a relatively cool, dark “hole.”

CATEGORIZED UNDER: Astronomy, select, Stars, Sun, Top Posts


ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.


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