October 10, 2005, Sunspot, NM--Adaptive optics technologies now available at the National Science Foundation's Dunn Solar Telescope at Sunspot, NM, are revealing striking details inside sunspots and hint at features remaining to be discovered in solar activity.
The images are made possible by the Dunn's recently completed AO76 advanced adaptive optics (Shack-Hartmann wavefront correction system) and a new high-resolution CCD camera. The ultrasharp image of sunspot AR 10810 shows several objects of current scientific interest. G-band bright points, which indicate the presence of small-scale magnetic flux tubes, are seen near the sunspot and between several granules (columns of hot gas circulating upward).
The dark cores of penumbral fibrils and bright penumbral grains are seen as well in the sunspot penumbra (the fluted structures radiating outward from the spot). These features hold the key to understanding the magnetic structure of sunspots and can only be seen in ultra high-resolution images such as this one. Magnetism in solar activity is the "dark energy problem" being tackled in solar physics today.
Normally such features are beyond the grasp of ground-based solar telescopes because of blurring by Earth's turbulent atmosphere. The Dunn's AO76 system compensates for much of that blurring by reshaping a deformable mirror 130 times a second to match changes in the atmosphere and refocuses incoming light. This allows the Dunn to operate at its diffraction limit (theoretical best) of 0.14 arc-second resolution, rather than the 1.0 to 0.5 arc-second resolution normally allowed by Earth's atmosphere.