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National Optical Astronomy Observatory News


Dr. K. S. "Bala" Balasubramaniam
National Solar Observatory

For More Information:
National Oceanic and Atmospheric Administration
Space Environment Center Boulder, CO
Barbara McGehan
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This picture of the largest sunspot group in a decade is a collage of images taken on March 27, 2001, at the National Science Foundation's Richard B. Dunn Telescope at the National Solar Observatory in Sunspot, New Mexico.

This whole sunspot covers more than 140,000 kilometers (86,8000 miles), 22 times the diameter of Earth, over the Sun's northern hemisphere. The images were acquired with a blue filter, called the G-Band, where carbon-hydrogen molecules are the primary source of light.

The Dunn Telescope is able to resolve features as small as 100 kilometers (62 miles) across on the Sun's surface. The darkest of the structures are the sunspot umbrae, where the magnetic fields are locally vertical. They are surrounded by lighter fibrous channels called sunspot penumbrae, where the magnetic fields are locally horizontal. The surrounding bubbly structures are known as photospheric granules, which are about 1000-2000 km (620-1,240 miles) across.

This large sunspot group is visible on the sun with the naked eye, when sufficient filters are used to prevent damage to the eyes.

The National Solar Observatory is operated by the Association of Universities Research in Astronomy, Inc.(AURA), for the National Science Foundation.

Credits: NSO/AURA/NSF (K. S. Balasubramaniam, M. Sigwarth, R. Radick, S. Hegwer, J. Elrod and S. Fletcher.)

More images...

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NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation. Last updated 30 March, 2001.

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