From John H The most detailed pictures ever taken of the Sun reveal the insides of striking snake-like filaments that reach from bright portions of the solar surface into the dark hearts of sunspots. The images promise astronomers a new way to reach deep into these magnetic beasts and extract their operational secrets.
Made with a specially equipped ground-based telescope, the photographs reveal features never before seen on the solar surface. The images themselves, and more important the technique used to make them, promise a fuller understanding of the complex and poorly understood interplay of matter and energy that roil the hot surface, all driven by the thermonuclear reactions at the Suns core.
Researchers at the Royal Swedish Academy of Sciences in Stockholm, led by Goran Scharmer, discuss the images in the Nov. 14 issue of the journal Nature.
Team member Dan Kiselman told SPACE.com what he sees in the new views of the Sun:
"A dark-cored filament looks like a glowing snake with a dark stripe painted along its back," Kiselman said. "The 'head' of the snake is often a complicated feature where the stripe splits up among many bright points."
The pictures were taken with academys recently installed solar telescope at La Palma, in the Canary Islands off the coast of Africa. Movies made by putting sequential images together show that that the dark cores of the filaments are long-lived and possibly more stable than the brighter portions.
The scientists also identified canal-like structures in the so-called penumbra of sunspots that "could also be described as a pattern of cracks," Kiselman said. The penumbra straddles a sunspots dark core and brighter regions elsewhere on the solar surface. "Whatever metaphors we use for these features, one should remember that everything is just glowing gas."
The photos were taken on July 15 and were colorized to highlight details. They were released today.
Mysteries remain
| Zoom In! | | Click on these images to zoom in on any portion with SPACE.com's Universal Viewer:  Large field-of-view image of sunspots in Active Region 10030. The image has been colored yellow for aesthetic reasons and to highlight detail.
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 Closer look: The highest resolution solar image ever shows part of the largest sunspot in Active Region 10030. The central region is dark because the strong magnetic fields there stop upwelling hot gas from the solar interior. The surrounding thread-like structures make up the penumbra. Dark cores, never before seen, are clearly visible in some of the bright penumbral filaments that stick out into the umbra. |
Detailed Views: Click to enlarge this set of pictures:  Panels a, b, and c show small sunspots, called pores, that have thin dark lines around their edges, dubbed hairs. The surrounding solar surface show dark lines seen as canals. Panel d shows penumbral filaments with dark cores; one of the filaments seems to be twisted. Tickmarks around the edge of the images show the scale. The distance between two ticks is 1,000 kilometers (621 miles).
IMAGES: Royal Swedish Academy of Sciences 
Sunspots seen by SOHO: This huge group of sunspots spanned a region 15 times larger than Earth. It was imaged by NASA's SOHO spacecraft on July 15, 2002 -- the same day as the Royal Academy's newly released images were made.
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Despite the detail the photos resolve things down to 62 miles (100 kilometers) -- researchers still dont know the details of how sunspots work.
"It is clear that everything we see is the result of the interplay of magnetic fields and the solar gas, or plasma," Kiselman explained. "The heat of the Sun tries to push through, carried by convection currents which are hindered by the magnetic fields. But exactly what happens and why these kind of structures are formed, we don't know."
Sunspots are cooler and darker than the rest of the Sun. They are launch pads for complex expulsions of plasma that race through the solar system, sometimes fueling the colorful lights near Earths poles known as aurora.
One might expect astronomers to have a firm grasp of the mechanics of our own Sun, it being by far the closest star around.
"Compared to other stars, one may say that it is true," Kiselman said. "But the amazing zoo of structures and dynamic phenomena on the Sun are not well understood in general, though they have been observed for a very long time."
So imagine how little is really known about other stars. "We will never understand any other star better than the Sun," he said.
SOHO much better
In terms of details, the photos beat a space telescope, the Solar and Heliospheric Observatory (SOHO). How is it possible to get finer images from the ground?
"SOHO simply does not have large enough telescopes," Kiselman said. The Canary island telescope has a 1-meter (3-foot) aperture. "Such a large solar telescope has yet to fly in space."
Telescopes are put in space partly to overcome the blurring effects of Earths atmosphere. Further, SOHO captures ultraviolet images of the Sun that can't be obtained from Earth.
As is often the case, ground- and space-based telescopes compliment one another in the overall study of an object.
The new images were made possible with adaptive optics, a system in which deforms mirrors to correct for atmospheric blurring.
John Thomas, of the University of Rochester in New York, wrote an analysis of the new images for Nature. Thomas says the newly discovered filament cores "are likely to be an important key to understanding the penumbra" of sunspots.
Thomas cautioned, however, that even higher-resolution images and observations of other types will be needed to figure it all out.
In fact, no one knows what is the lower limit of discernable structures on the solar surface. Eventually, he said, larger telescopes with adaptive optics might be able to see structures as small as 0.6 miles (1 kilometer).
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