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Spicules on the Sun's Surface
This image, taken at the Swedish 1-meter Solar Telescope (SST) on the island of La Palma, Spain, shows Active Region 10380, photographed on June 16th, 2003 towards the limb of the sun. The image was taken through a filter in so-called "H-alpha" light emitted by hydrogen atoms at a wavelength of 656 nm in the solar spectrum (reddish light). This part of the solar spectrum is mostly emitted by the chromosphere: the layer of the Sun's atmosphere just above the solar surface. For this image, we used the Lockheed tunable filter which allows us to fully exploit the Doppler effect and focus exclusively on "blue-shifted" light emitted by features coming towards us. That is why the (right half of the) image is dominated by a "lawn" of short, dark features, called spicules: they are jets of gas moving towards us at speeds of ~30,000 miles/hour. Also visible in the upper left quadrant are some small sunspots (where the magnetic field is very strong), and large fibrils or magnetic loops connecting the sunspots. The brighter regions are so-called "plage" regions, also caused by stronger than average magnetic field, usually organized in small "flux tubes". This image is one of the highest resolution images ever taken of the chromosphere of an active region on the Sun, showing details of only 80 miles! The whole area shown here measures about 40,000 miles by 27,000 miles on the Sun, with the spicule jets measuring about 300 miles in diameter, and a length of 2,000 to 5,000 miles. For comparison purposes, the Earth's diameter is about 8,000 miles, whereas the Sun measures 870,000 miles in diameter.