An observatory in the mountains of southern New Mexico that is dedicated to unlocking the mysteries of the sun has found itself at the center of a mystery that is creating a buzz here on earth. Authorities [say] only that an undisclosed security concern was behind the decision to abruptly vacate and lock up the remote facility on Sept 6. The Sunspot Solar Observatory has been closed for more than a week. The FBI referred all questions to the group that manages the site, the Association of Universities for Research in Astronomy. The vagueness continued to fuel speculation. The telescope at Sunspot was originally built by the U.S. Air Force. After several years of operation, it was transferred to the National Solar Observatory, which is part of the National Science Foundation. Sunspot's one-of-a-kind telescope produces some of the sharpest images of the sun available in the world, officials said.