In May 2002, the Swedish 1-m Solar Telescope (first image above, 1 MByte) started operation with its full aperture. During the first few months of operation we collected many solar images with unprecedented spatial resolution, estimated to approximately 90 km. Some of these show inner structure, a dark core, in the hitherto unresolved filaments in sunspot penumbrae. The second image above (20 KByte) shows the entire solar disk as it looked on July 15. The third image (250 KByte, tick marks are 1000 km apart) shows part of the sunspot group near disk center. The fourth image (200 KByte, 1000 km tick marks) shows part of the larger spot, where several dark core filaments are visible. A sample dark-cored filament is shown in the fifth image (5 KByte, 100 km tick marks).
The dark-cored filaments were an unexpected discovery, that we have published as a Letter in Nature, "Dark cores in sunspot penumbral filaments" by Göran B. Scharmer, Boris V. Gudiksen, Dan Kiselman, Mats G. Löfdahl, and Luc H. M. Rouppe van der Voort, 14 November 2002.
We also have a movie in quicktime and mpeg formats, that shows how the same field of view develops during half an hour of observations. (The mpeg movie is B/W and has lower quality. On the other hand, we know the quicktime movie does not work everywhere. The best way to make it work is to download it to the local computer, start the appropriate viewer program and open the quicktime file from there.)
The images may be published if you give credit to the Royal Swedish Academy of Sciences.
If you need these images for professional publishing, please go to the image and movie download page, where they are available in a number of different formats and sizes.
There is more background information, mainly for journalists, and if you are a solar scientist you may want to analyze some of the data.