Sundancing. (Astronomy).Astronomers say they have solved the mystery of why supergranules--enormous cells of turbulent, charged gas that pepper the sun's visible surface--appear to move across the sun faster than the sun rotates. Data taken by the SOHO Soho (sōhō`, sə–), district of Westminster, London, England, known for its continental restaurants. Once a fashionable quarter, it became popular among writers and artists in the 19th cent. (Solar and Heliospheric Observatory The Solar and Heliospheric Observatory (SOHO) is a spacecraft that was launched on an Atlas IIAS launch vehicle on 2 December 1995 to study the Sun, and began normal operations in May 1996. ) spacecraft reveals the motion as an optical illusion. The supergranules undulate undulate /un·du·late/ (-lat) 1. to move in waves or in a wavelike motion. 2. to have a wavelike appearance, outline, or form.un´dulatory , and it's the wave they form that races ahead of the sun's rotation. Researchers liken lik·en tr.v. lik·ened, lik·en·ing, lik·ens To see, mention, or show as similar; compare. [Middle English liknen, from like, similar; see like2 the phenomenon to people in a stadium doing the wave. Each person jumps up and then sits back down, creating a wave that moves across the stadium even though no one is actually moving beyond their seat. Similarly, the bobbing of supergranules "is just a pattern of activity that is moving across the solar surface in waves," says SOHO astronomer Tom Duvall of NASA's Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C. in Greenbelt, Md. Duvall and his collaborators, who report their work in the Jan. 2 Nature, relied on SOHO's Michelson Doppler Imager to make their measurements. The device measures the velocity of material at the solar surface so that scientists can discern the movement and structure of gases both on the surface and far beneath.--R.C. |
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