SAN FRANSICO — Astronomers who study the sun have a new image to contemplate - a knobby star.
Early data from a new European-American orbiting solar observatory show our star is covered with knob-like features. They measure about 60,000 miles across (five Earth diameters) and a half-mile high. On a solar scale, that makes them too small to have been seen by any Earth- or space-based solar observatory before.
Shown for the first time at the fall meeting here of the American Geophysical Union, the knobs appear to be a significant feature of the sun's outer layer. Ed Rhodes of the University of Southern California at Los Angeles told a press conference that theorists had predicted such features should exist. If the knobs prove to be a permanent solar element, he says, it is reasonable to think they play a significant role in the mechanisms that bring energy from the interior to power solar activity and sunshine.
Meanwhile, the sharp view of the new, $1.1 billion satellite may have settled a debate over whether the sun's shape is inconsistent with Einstein's general theory of relativity, and how fast the sun's core region rotates. Jeff Kuhn of Michigan State University reported that new observations show the sun, instead of having a slightly squashed shape, is essentially a perfect sphere "and Einstein's theory is safe." He added that some theorists suggested that the core region rotates quite rapidly compared with the rest of the sun. The fact that the sun shows so little flattening rules that out.