Gamma glow from the moon.Viewed at wavelengths from visible light to X rays, the sun is our solar system's star performer. Observed in the light of gamma rays Gamma rays Electromagnetic radiation emitted from excited atomic nuclei as an integral part of the process whereby the nucleus rearranges itself into a state of lower excitation (that is, energy content). , however, the moon outdazzles the sun. Images taken recently by a telescope aboard the Comp-ton Gamma Ray gamma ray Penetrating very short-wavelength electromagnetic radiation, similar to an X-ray but of higher energy, that is emitted spontaneously by some radioactive substances (see gamma decay; radioactivity). Observatory (GRO GRO Guerrero (Estado de México) GRO General Register Office (UK) GRO Greater Research Opportunities GRO Gamma Ray Observatory GRO Growth-Related Oncogene GRO Greensboro, North Carolina ) provide graphic evidence of this phenomenon. "As far as we know, no other branch of astronomy sees the moon brighter than the sun," says GRO investigator David J. Thompson 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. The gamma glow occurs when high-energy cosmic rays-the charged particles streaming in from distant regions of the galaxy at nearly the speed of light- smash into the moon. They excite the nuclei of atoms on the lunar sur-face, which then emit gamma radiation. Unlike the moon, the sun possesses a magnetic field. This field acts as a shield, deflecting cosmic rays cosmic rays, charged particles moving at nearly the speed of light reaching the earth from outer space. Primary cosmic rays consist mostly of protons (nuclei of hydrogen atoms), some alpha particles (helium nuclei), and lesser amounts of nuclei of carbon, nitrogen, and other incoming charged particles. Gamma radiation from the sun is thus too faint to be detected by the GRO telescope, except when turbulent activity triggers a solar flare. |
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