Solar Portrait

Tuesday, September 01, 1998
These images of the sun are among the first captured by the ultraviolet-light telescope of a new NASA space probe. The Transition Region and Coronal Explorer, or TRACE, spacecraft, launched April 1, snaps one picture of the sun every 20 seconds or so, 24 hours a day, seven days a week. Every morning, Alan Title and his colleagues at the Stanford Lockheed Institute for Space Research in Palo Alto, California, sit down to watch movies compiled from the images. Aside from providing wide-eyed earthbound researchers with pretty pictures, TRACE offers solar physicists the best resolution yet of the fine details of the sun's outer atmosphere. Each of these images, taken by TRACE on April 25 and 26, shows about one-sixteenth of the sun's surface. The smallest loops visible-which consist of electrically charged particles, or plasma-are only about 200 miles wide. Such definition could not be obtained with previous instruments. "You saw just blurred-out loops," says Title. "You didn't see all this interior fine structure." The pictures reveal that the loops of plasma can be close neighbors yet have very different temperatures. Here, blue indicates about 800,000 degrees, green about 1.5 million degrees, and red about 2.7 million degrees. (The bright spot in the photo above is a sunspot.) The largest loops visible in these two images could contain 15 Earths.
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